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I briefly spoke with vintage Chief in my previous thread about this issue and was advised to move it to a new topic.
My 71 olds cutlass has undergone a hefty project over the past year in my garage. The engine and trans has been rebuilt with an eye on daily driving and modest power increases.
However I have been dealing with overheating issues since the rebuild stemming from the radiator emptying around a gallon of coolant out of the overflow in a matter of minutes when the vehicle is accelerating. Idling it is fine, and in the garage not in gear it can be revved to any reasonable rpm without spitting up coolant but after a drive with any degree of acceleration requiring more than 2500 rpms the coolant will coat the passenger side of the engine bay.
I tried high flow thermostats and no thermostat and the problem persisted. It took a little longer when the thermostat was removed for the car to overheat but not much. When the radiator is full it flows well, I don’t see any bubbles forming in the tank. When the radiator is low after a drive it barely trickles through the tank.
350 engine, flat top pistons, #7 heads, custom grind cam from comp cams with barely over stock lift but longer duration, .030 over bore, moly rings, 145-155 psi compression on all cylinders with compression tester.
My running theory was a blown head gasket allowing compression into the coolant supply or a clogged radiator. Am I heading in the right direction? The radiator in the car is a copper/brass three core unit with built in trans cooler. I am using the factory 19.5” clutch fan and shroud with new clutch and water pump. Both are in good working condition. 16 pound cap on radiator. No leaks from system during pressure testing from radiator
with thermostat removed and held vacuum as well.
I have not performed a leak down test yet on the motor but am going to try to borrow the tool this weekend to test it.
Last edited by markvii1; September 9th, 2020 at 08:23 PM.
For a suspected head gasket issue, you can rent a test kit tool from the local auto parts store that uses a chemical to test for combustion gases (specifically CO2) in the cooling system. Easy to use and extremely sensitive - I checked the one I used and the chemical changed color when I breathed on it, that's how sensitive it is.
In my case, I ruled out a head gasket problem using the test kit and was able to continue investigating other issues.
most of these cars had no overflow tank. The rad is made to be filled about 2" below the filler hole, if you fill to the top the excess will spew right out
it looks like youve covered most of the usual suspects but what is the operating temps ?
I removed the overflow tank after it blew the lid off of it. It was crudely installed by the previous owner and had no way to recycle coolant back to the radiator. Currently it drains to the ground. I leave about two to three inches from the top of the rad and fill it with the engine running and heater on to ensure air escapes and all avenues for the coolant to go to are filled.
I don’t know exact temps as I installed the rally gauge set correct for the year and it does not have numbers in the gauges but it will run at normal temperatures until the coolant has been ejected which is usually about a gallon and then it will run hot. I have tried to minimize running it while above the three quarter mark on the temp gauge. I keep a bottle of coolant with me for emergencies but lately I haven’t been able to drive it all as the problem has accelerated.
(1) Be certain you have the correct lower (inlet) radiator hose. The lower radiator hose must be of the style which maintains solid rigidity. If the lower (inlet) radiator hose does not maintain solid rigidity, there exists the possibility the lower radiator hose will collapse - preventing coolant from entering the engine (in particular during high RPM under acceleration). The lower radiator hose is the suction end of the system - coolant is being drawn (sucked) into the system via the water pump. If it collapses, well...you get the idea. Many parts houses out there - all wanting to sell product and many selling the incorrect product. If I'm not mistaken, the OEM lower radiator hose had the spring coil metal insert which maintained solid rigidity of the lower radiator hose. It's critical the lower radiator hose is not thin wall flexible style which can collapse. I suppose you could run (accelerate) the engine while driving, and when it pukes coolant, stop & grab (it's hot most likely) the upper radiator hose. If the system is under pressure you should be able to feel a rigid upper (outlet) radiator hose filled with circulating coolant. If the upper (outlet) radiator hose is not rigid with coolant running through it, check the lower (inlet) radiator hose to see if it has collapsed.
(2) Double-check your water pump model number and double-check it is the correct model for your vehicle. I understand it fits and appears to be working. At this point let's check all the basic points. A proper water pump will not produce "baffling" under acceleration. IOW, there should be a steady stream of coolant flowing. The propeller on the water pump must not produce a baffle effect. Double-check the water pump model number.
I do not believe the lower hose has the spring inside it- it is very flexible. I cannot find the original order I placed for the new water pump but if memory serves it was an AC Delco water pump for an Air Conditioned 71 Cutlass 350. The length of the pump puts the fan in the correct orientation to the radiator and shroud and I compared it to the old one before installing it (now that the correct motor mounts are installed). If I can find the part number tonight I will post it to verify. Can I purchase the spring for the lower hose or is there a correct lower hose that will have the spring inside it?
Just ordered a lower hose and inner spring from the parts place - hopefully this will help with my issue. I hadn't even considered the lower hose being a problem as it's difficult (impossible) to be under the hood when the car is chucking coolant to check the hoses.
Last edited by markvii1; September 10th, 2020 at 05:42 AM.
Obviously the length of the water pump shaft is critical for pulley alignment, but that is not what I am making reference to. I am referencing as stated the water pump propeller contained within the water pump. It most likely is the correct water pump but we’ve all seen aberrations. The propeller need to be of the correct style/dimensions in order for the propeller blades to sufficiently move water through the water pump without creating a baffle where you’re moving more air than water. Think of a boat propeller with the incorrect pitch which spins/rotates but never grabs enough water to propel the boat. Again, chances are it’s correct but double-checking is harmless assurance.
i believe you discussed radiator caps earlier in the other thread, You said there was a jerry-rigged overflow tank, if that is what it was and you removed it. You know this car never had an OEM overflow reservoir. Note there are basically two types of reservoirs: (1) Is nothing more than a puke tank to contain overflow; (2) The other is not a simple containment reservoir but will also return fluid to the radiator. I don’t know which type you removed. The second type would be maintained under pressure, the first type is not maintained under pressure - it’s just a puke tank to catch overflow. In any case, you only need a hose connect to the overflow vent outlet running down the side of the radiator with the correct radiator cap. Some radiator caps are terribly made. You need nothing fancy here. A very plain Jane simple 16 psi cap. I believe you stated in the other thread you tested a radiator cap in hot water and called it good. Temperature is not the critical piece of the puzzle - it’s the pressure of the valve and spring of the radiator cap. Does it ‘maintain’ pressure? That is the critical piece.
I tested the thermostats in hot water for proper function and they all worked. I have installed two different 16 psi radiator caps - both were simple cheap caps from the local parts store but the seals were good. The tank that was on the car was just a "puke" tank that was sheet metal screwed through the upper support cover - not a factory correct part. Right now I just have a rubber hose running from the overflow on the radiator down the side of the radiator to exit under the car. I guess the pressure on the line when the car is operating causes it to spray like a fire hose with no one holding it down and that allows the coolant to spew all over the passenger side inner fender. I will try to find the box the water pump came from to cross reference part numbers.
I had an issue with the radiator caps for my 72 Cutlass. They tested fine but did not seal well on the radiator neck when hot. I finally found that the Delco 12R7S cap had a full upper seal unlike some of the others. This cap fixed my problem.
Last edited by Will22; September 10th, 2020 at 07:32 AM.
I tested the thermostats in hot water for proper function...
My bad! I was mowing the lawn between showers & had a momentarily lapse of reasoning. For some reason I mistakenly thought I recalled you tested the radiator caps. Doh.
Note there are basically two types of reservoirs: (1) Is nothing more than a puke tank to contain overflow; (2) The other is not a simple containment reservoir but will also return fluid to the radiator. I don’t know which type you removed. The second type would be maintained under pressure, the first type is not maintained under pressure - it’s just a puke tank to catch overflow.
There's actually a third type of system (not overflow tank) that is a non-pressurized coolant recovery system. It utilizes the non-pressurized overflow tank and a radiator cap with a return valve in it so that the coolant in the overflow tank is drawn back into the radiator when the engine cools.Basically a catch-can with return capability.
Aftermarket sucko radiator caps are common in the ricer world, quite common and the first thing that is looked at when you start having overheating issues that weren't there before. It's OEM for me.... Tedd
I had an issue with the radiator caps for my 72 Cutlass. They tested fine but did not seal well on the radiator neck when hot. I finally found that the Delco 12R7S cap had a full upper seal unlike some of the others. This cap fixed my problem.
Heard an old Olds specialist explain once that the radiator opening can sometimes get "bent" in such a way that the cap seal does not fit the radiator opening correctly. The fix was to eyeball it closely and torque on the cap to correct the alignment. The pressure tester may have enough articulation to the seal that it will in fact seal the radiator but the cap will not. Just a thought.
Caps are made cheap and radiatore have been getting thinner in construction and can warp or dent. In the last five years I've had two caps not seal when pressure gets close to max, Seal fine till they get on a extended pull or a extremely hot day. It's hard to find especially if you are not looking at the right place.....Tedd
I ordered a lower hose spring and installed it this evening. I’m no longer spewing coolant from the radiator and the temps stay nicely between the 1/4 and 1/2 mark on the temp gauge with 180 degree stant super stat installed. Also installed stant 16 lb OE style radiator cap for good measure.
Will attempt longer drive tomorrow with some highway miles to make sure. Thank you for the ideas I never would have thought to check the lower hose otherwise.
Hopefully you found the issue. I suspected the lower radiator issue primarily because you stated it occurred during acceleration but not at idle. At acceleration you're drawing significant amounts of coolant from the lower hose and if it has collapsed, there's no coolant entering the block and basically it's going to boil over and puke out the overflow. GL
The entire cooling system has "radiator cap" pressure on it when hot, and the engine is shut off. Pressure is equalized in a static system. Let's say 16 psi.
Run the engine. The "suction" side of the water pump reduces the pressure, while the outlet(s) of the water pump increase the pressure. No pressure differential, no coolant flow. Pressure is not equalized in a dynamic system. The amount of pressure differential will depend on how, where, and how much the coolant flow is restricted.
All the above is basic hydraulic theory: static vs. dynamic systems.
The thermostat is the intended restriction, mounted in a rigid, metal or strong composite assembly called "the engine", notably AHEAD of the long and non-rigid upper rad hose. Given this placement of the thermostat, the upper rad hose is on the suction side of the water pump. There can be multiple restrictions that aren't intended. A plugged radiator and/or heater core would be towards the top of the "likely suspects" list.
So if your lower hose is "sucking shut", the first thing I'd look for is a RESTRICTED RADIATOR, (which has the effect of causing the upper hose to be part of the pressure side of the water pump, not the suction side) the second thing would be rotted upper rad hose, or ancient heater hoses, and the third thing would be a coiled support (spring) in the lower hose. That lower hose is getting pressurized by the rad cap at ~16 psi, minus the suction of the water pump. How could it ever collapse?. Excess restriction coupled to high water pump RPM would do it. Especially when the rest of the cooling system hoses (upper rad hose in particular) are towards the end of their service life, so that they balloon excessively under pressure.
With the radiator restricted, and the other cooling system hoses expanding under pressure, the water pump is trying desperately to pull coolant out of the rad, and push it into the engine and those expanding hoses. In essence, it's moving a considerable volume of water OUT of the lower hose, and INTO "everywhere else". The lower hose doesn't have a large internal volume to begin with, much less than the entire rest of the hoses. As those hoses expand and increase the volume of coolant they contain...the one on the suction side collapses and reduces it's volume..
Last edited by Schurkey; September 16th, 2020 at 01:29 PM.
Do not confuse system pressure vs flow pressure. The system operating pressure is not determined by the cap, the cap determines at what point the system gets relief, it is a popoff valve. There is no telling which corrected the issue since multiple things were changed at once.
Do not confuse system pressure vs flow pressure. The system operating pressure is not determined by the cap, the cap determines at what point the system gets relief, it is a popoff valve.
Yes, that's exactly what I'm trying to get across.
The cooling system, with the engine running and the water pump moving water (creating a pressure differential) can be divided into the "high (pressure) side", and the "low (pressure) side", with the primary restriction (thermostat) and the pump being the dividing points. From pump impeller to the thermostat, you're seeing rad-cap pressure PLUS pump pressure; from the thermostat back to the water pump impeller you'd have rad cap pressure MINUS water pump "suction". The difference would be more dramatic as the thermostat closes, and less dramatic as the thermostat opens.
Of course, there's some flow restriction everywhere in the system--around the engine block and head water passages, through the hoses, through the tubes of the rad or heater core, etc. But the main restriction would--and should--be the thermostat, particularly when closed or open a small amount. When closed so there's almost no flow, the upper rad hose is strongly affected by the suction side of the water pump. With the thermostat open, the upper hose is less affected by the suction side of the pump. When the radiator is more of a restriction than the thermostat...the upper hose is more affected by the pressure side of the pump, so that upper hose sees rad cap pressure PLUS water pump pressure, and it balloons even more.
And the volume of coolant held by that ballooned hose on the pressure side, has to come from somewhere on the suction side. That means the lower hose collapses as the upper hose expands.
Last edited by Schurkey; September 16th, 2020 at 05:39 PM.
I ordered the lower hose from the parts place
thepartsplaceinc.com
However I ended up having to pull the thermostat out gain today after a longer drive as it was not opening and the upper hose was remaining cool. I tried to burp the system but that didn’t help for long. So now I’m back shopping for a radiator again. That spring is certainly staying in the lower hose though.
Summit sells a three row solid aluminum radiator 33” x 18.6” x 2.75” for $299 with good reviews. Measured against my radiator it is around a half inch less wide and a half inch taller so should squeeze into place easily enough until I can get me original rad recored.
Will update further once I have tried a new radiator.
I tried to burp the system but that didn’t help for long.
You should only need to remove the radiator cap & let the engine run for ~20 minutes until it reaches operating temperature at which point the thermostat should open allowing the coolant to flow through the system; then, allow it to run maybe another 15 minutes with the radiator cap off. That should be good enough to remove air from the system. Then, fill the radiator to ~1" below the bottom of the radiator cap neck inlet. Then, replace the radiator cap and allow the pressure to build. Did the upper radiator hose get firm with coolant moving through it? Is that pretty much how you did it? Tough one to figure out here, I thought earlier in the posts you said you could see coolant moving through the radiator quite well at idle. Is that not the case any longer? If coolant is flowing quite well through the radiator and you can visually validate coolant moving through the radiator it's becoming more confusing (to me anyways). Is it still puking coolant when you drive it? I thought earlier you were good to go? Baffling is what it is.
Last edited by Vintage Chief; September 16th, 2020 at 04:20 PM.
Reason: sp
Installing the spring in the lower hose seemed to help the problem, it ran well for about two days with the thermostat in place, then the car would warm up past the normal threshold that the thermostat would open and would head almost to the top of the gauge before the temperature would drop. I pulled the cap off the radiator and noticed that coolant was barely trickling through again. I checked the upper hose and it was cool. The only piece of the puzzle left is the radiator. I have no idea how old it is and every other piece of the puzzle is new, rebuilt, checked and replaced. I’ve never experienced a similar problem to this before, but reading the posts above makes me think that a clog in the radiator puts the wrong pressure on the upper hose causing the thermostat to stay closed because the thermostats all test well in hot water on a stove. I thought today I had air trapped in the system but it did not help when I ran the car up to temp squeezing the hoses with the radiator cap off. The upper hose remained lukewarm.
My old-school manner to check for a significantly clogged radiator generally works pretty well. (1) Run the engine to operating temperature, ensure the fan is operable, turn off the engine. Place the palm of your hand on the fins of the radiator moving from an interior concentric circle outwards towards the periphery and note any serious hot spots and any serious cold/cool spots. Perform this on both sides of the radiator. (2) Visually check the condition of the fins on the front & back for external debris. (3) With the engine at normal operating temperature, the temperature of the lower radiator hose should be much cooler than the temperature of the upper radiator hose. (4) Run the heater with the engine at normal operating temperature, the heater should produce consistent hot air. (5) Place a bucket under the radiator & remove the radiator cap, remove the lower radiator hose, loosen and/or remove the upper radiator hose from the radiator & drain the radiator. Pour water into the radiator from a gallon container. The amount of water existing the radiator should approximate the same amount of water you pour into the radiator at approximately the same rate. It should not flow out the bottom significantly slower than you're pouring water into the radiator. (5) With an IR temperature thermometer, take readings of the radiator as I previously noted in (1) check for wide swings of variation in temperature (e.g. 40°F - 50°F). (6) Take note of significant discoloration of coolant and/or water exiting the radiator. Obviously you can't perform (5) without a temperature probe but they're not too expensive and often available at supply houses. Obviously if you had a temperature probe you could shoot the temperatures of both the upper and lower radiator hoses as well.
Last edited by Vintage Chief; September 16th, 2020 at 07:40 PM.
I may not be the fastest at troubleshooting but I try to be methodical & deliberate. I'd have to thoroughly convince myself above all, that coolant was absolutely moving through the system via the water pump. You just are not going to get ANY water moving through the system without a functioning water pump. Brand new water pumps are known not to work. The majority are re-manufactured - somewhere by someone. Many other very knowledgeable members here to help you out through this.
I may not be the fastest at troubleshooting but I try to be methodical & deliberate. I'd have to thoroughly convince myself above all, that coolant was absolutely moving through the system via the water pump. You just are not going to get ANY water moving through the system without a functioning water pump. Brand new water pumps are known not to work. The majority are re-manufactured - somewhere by someone. Many other very knowledgeable members here to help you out through this.
this^
When I first put the aluminum heads on my car probably 20 years ago, I drove the car for about 20 minutes, everything was fine. Then it would overheat, and overheat quick! You can imagine my concern, I was freaking out thinking I had heads with a bad casting, I had screwed up the installation, I figured whatever the cause, it was going to be expensive to fix. After eliminating the usual causes, I decided to inspect the water pump. I removed the pumps d didn’t see anything obvious, but when I set it down I heard a clink. When I picked the pump back off the workbench, the impeller was still on the bench. The pump wasn’t all that old, and had worked just fine until I installed the new heads.
Not always, but generally, a fast/fair diagnosis of the water pump is to check (1) the cabin heater. The heater should consistently deliver hot air at idle and at operating temperature. While you're accelerating/driving the car, turn the heater on, it should deliver hot air. Let's assume the heater core is functioning at this point at least. A major heater core issue your passenger compartment floor would be soaked with coolant and smell of coolant. (2) Perform the grip test on the upper radiator hose. With the engine cold and not running, grip the upper radiator hose & squeeze it. The upper radiator hose should be very flexible and very easy to collapse in your hand. More or less attempt to bend the upper radiator hose firmly in your hand to sense the flexibility of the hose with no water circulation. Either turn the car on and let it idle or rev the RPMs for 10' - 15' until the engine achieves normal operating temperature or take it for a quick ride. Grip/Grasp the upper radiator hose either with or without a functioning thermostat, the upper hose should now be firm and squeezing and twisting/flexing the upper radiator hose you should be able to feel coolant running through the upper radiator hose. You're not looking for pressure here, you want to feel water moving through the hose. (3) Perform the backyard diagnosis as described in the video link (below). You can make this for a couple dollars. You really don't need the food coloring dye and you can put the food coloring dye into the radiator before you test. The point being you should be able to clearly visualize water moving from the engine into the radiator via the upper radiator hose.
The heater works well in the car - as long as coolant is in the system I have consistent heat in the car. It always blows slightly warmer air in the car than the air outside (probably a blend door issue, haven't opened the evaporator case to inspect) but when I ask for heat I get it. There is no smell of coolant in the car and no wet carpet under the dash.
One other thought, are you absolutely sure all the air is out of the cooling system? The easiest/least messy way I have found is to jack up the pass front corner, make sure the radiator cap is the highest area of the cooling system. Leave the cap off overnight, if there is any air in the cooling system it will naturally “burb” out by the heavier coolant settling in the space previously occupied by the air. If the coolant level drops overnight, it had air in the system.
It could have had some air in it on the last test drive, but even when I filled the system before using a vacuum pump the issue persisted. My current running theory is that the radiator is blocked to an extent that it is increasing pressure on the system and cannot move the volume of coolant through itself fast enough that the water pump is pushing. With the thermostat in place the upper hose was hard and full of fluid but it was all cool to the touch. The thermostat never opened because the radiator backed up the coolant through the upper hose and kept one side of the thermostat cool. At least that is my theory, I am going to get temperature readings on it tonight to make sure.
It was the radiator. Bottom was much cooler than the top and wouldn’t drain completely without shaking and turning on its end to empty out of the lower hose opening. Installed a new all aluminum radiator from summit racing.
If anyone is looking for a good drop in radiator that required no modifications and worked with the factory top plate, fan shroud and trans cooler lines then try out this radiator. Summit 384000. https://www.summitracing.com/parts/s.../model/cutlass
It comes with a cap but it is crap. The factory cap fits on the opening however. I used the stant 16lb cap I bought recently and it fit perfectly. The radiator even sits in the rubber perches on the top and bottom perfectly.
The tanks are polished aluminum tig welded to the core and it has a three row core. It only cost $318 with tax and shipped to me in two days. So far I’m very pleased.
Temperature stays rock solid right where the 180 degree thermostat should keep it even under load.
It was the radiator. Bottom was much cooler than the top and wouldn’t drain completely without shaking and turning on its end to empty out of the lower hose opening. Installed a new all aluminum radiator from summit racing.
If anyone is looking for a good drop in radiator that required no modifications and worked with the factory top plate, fan shroud and trans cooler lines then try out this radiator. Summit 384000. https://www.summitracing.com/parts/s.../model/cutlass
It comes with a cap but it is crap. The factory cap fits on the opening however. I used the stant 16lb cap I bought recently and it fit perfectly. The radiator even sits in the rubber perches on the top and bottom perfectly.
The tanks are polished aluminum tig welded to the core and it has a three row core. It only cost $318 with tax and shipped to me in two days. So far I’m very pleased.
Temperature stays rock solid right where the 180 degree thermostat should keep it even under load.
Awesome. Thanks for following up with an excellent resolution synopsis. Happy motoring!
September 9th, 2020, 08:21 PM
