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i could use some help here.
my ‘73 delta 88 with 350 engine keeps overheating.
i already replaced the waterpump,the radiator. ( installed a 3 row aluminium unit) and the thermostat. (195 degrees).
still the engine overheats even when just idling.
i inspected the cooling fan with visco clutch and it is functioning correctly too.
i now suspect the cooling channels in the engine to be silted up with rust. Especially since the old and replaced waterpump was seized up because of rust.
any suggestions of how and with what agent to derust the cooling channels in the engine block and heads?
any input is appreciated! I’m out of options here.
Is the coolant boiling over. If you have a temp gauge, how hot is it getting? I was having a similar problem with my car with a 455. Turned out the fan clutch I thought was good wasn’t. I put a new Hayden heavy duty clutch and a high flow t-stat and problem solved. That being said my temps still get to 210 in heavy traffic. If you had restrictions in the water jackets you would have higher temps at higher rpms and speeds. Not just at idle. High idle temps is usually indicative of air flow problems.
Sorry for the confusion.
when i start the engine temps rise to 220 degrees and stays there. Idling or highway cruising makes no difference. It stays at 220 degrees. Only when i remove the thermostat the temp drops significantly.
What did the temp drop to with it removed? A thermostat maintains the minimum engine temperature. Since the temp dropped when you removed the thermostat, see what happens if you install a 180* thermostat. Thermostats may not fully open for up to 15- 20* above the stated temp.
I think you have a bad thermostat. Most manufacturers mass produce thermostats & have extremely limited quality control standards (if they have any at all).
You demonstrated, IMO, the thermostat is bad if you remove it and the temperature drops significantly (although you didn't state what that is).
STANT makes the best cooling system components, IMO - I'd only buy a STANT radiator cap &/or thermostat.
Your vehicle should use STANT Part # 45358
You can order from any local automotive parts store or on-line from many vendors - here's the RA link: https://www.rockauto.com/en/catalog/...hermostat,2200
I say a Robert Shaw 180 high flow Thermostat. Your 220 degrees is on the borderline temp, new vehicles run that hot. Use a temp gun to check your gauge accuracy. Also make sure all the directional flaps around the radiator are in place and not damaged.
Last edited by olds 307 and 403; June 17th, 2022 at 08:02 PM.
When driving or idling the car without a t-stat temperature drops till 160 degrees. Ambient temperature is 70 degrees.
ran into a traffic jam one day. Running the car without t-stat and temperature rose quickly to 220 degrees again.
i bought a new t-stat this morning. A stant 180 degrees. Before installing it i tested it in a pan. Warmed up the water on my stove with the t-stat and a kitchen thermometer in the water. To my surprise the t-stat didn’t start opening till the water reached 194 degrees!? It was fully open at 212 degrees. Did this test 3 times. Same outcome every time. Is this a faulty t-stat,or am i interpreting it wrongly.?
haven’t installed this t-stat till now. Not sure if i should.
When driving or idling the car without a t-stat temperature drops till 160 degrees. Ambient temperature is 70 degrees.
ran into a traffic jam one day. Running the car without t-stat and temperature rose quickly to 220 degrees again.
i bought a new t-stat this morning. A stant 180 degrees. Before installing it i tested it in a pan. Warmed up the water on my stove with the t-stat and a kitchen thermometer in the water. To my surprise the t-stat didn’t start opening till the water reached 194 degrees!? It was fully open at 212 degrees. Did this test 3 times. Same outcome every time. Is this a faulty t-stat,or am i interpreting it wrongly.?
haven’t installed this t-stat till now. Not sure if i should.
That is "as designed". Read the link(s) I provided to you (above). I'll quote the most important:
Thermostats have a “rated” temperature (such as 180F or 195F). This is the temperature the thermostat will start to open, releasing heated coolant from the engine into the radiator. The thermostat will fully open once the coolant gets another ten or fifteen degrees warmer.
BTW: I should point out. Your test is not identical to an installed thermostat. Your pan has no laminar flow; instead, it is static. An automotive thermostat is deigned to operate under pressure - which, you have no pressure in a warm pan of water.
Last edited by Vintage Chief; June 18th, 2022 at 05:38 AM.
Get a Robert 180 Thermostat. I find the 160 and 180 open pretty exactly where they should on the gauge. Yeah, a new heavy duty fan clutch will help, especially at idle and low speeds. Make sure all air direction flaps are in place. The 3 core is OK but not ideal. It should still cool a stock 350. A large 2 core aluminum rad with 1"+ tubes, mine are 1 1/8", some are 1 1/4", will definitely out cool that 3 core and a 4 core as well due to better air flow through the cores. What size is the radiator in the 88? I assume, pretty big.
Sorry for my late reaction.😳
no it is not resoved yet. Haven't had much time to adress it the last few days.
my plans are to install the old radiator again,bypass my new heater core and remove the thermostat.
then i want to fill up the cooling system with a mix of water and oxalid acid. (10:1). Drive the car for a while and repeat that until the water stays clear when i let it out of the system. At this point the water turns black the moment i pour it in the engine.
i will report my experiences here in this topic of course.
thanks for all your input and help!
Btw . To my knowledge Oxalic acid is one of the most potent rust inhibitors as it comes to acids. Curious to learn what your opinions are..
I used acid as well, it really removed the scale from inside the radiator. CLR is supposedly latic acid and gluconic acid. I may have used citric acid as well. Even if the original rad doesn't cool as well, it is better to use acid in the Copper Brass than in the aluminum rad. I just installed this rad in my 70S, I plan on putting some serious warm weather miles on it. So far, it barely moves the gauge around town, back and forth to work in my 70S. It is a 2 core with 1 1/8" tubes. The good aluminum radiators require 4 core saddles. I wasn't super impressed with my Champion 3 core aluminum as far as cooling ability. https://www.ebay.ca/itm/351157989603...mis&media=COPY
then i want to fill up the cooling system with a mix of water and oxalid acid. (10:1). Drive the car for a while and repeat that until the water stays clear when i let it out of the system.
Btw . To my knowledge Oxalic acid is one of the most potent rust inhibitors as it comes to acids. Curious to learn what your opinions are..
Interesting. My HS auto shop engine class instructor who I considered the best auto mechanic at the time taught us to use oxalic acid to clean cooling systems. Never did try it though. I like your idea of bypassing the new heater core and reinstalling the old radiator for the purpose of saving your new parts from the effects of the acid. Sounds like some thought went in to this. A concern I would have is the core plugs. If the block is rusted up and the core plugs are original the acid and rust removal more cause them to leak during the rust removal or start to leak in the future. (I've have this happen on costumers cars over the years) I have also seen the OEM steel shim head gasket start to leak during the cleaning process. I recommend you remove the thermostat before chemical flushing the system and leaving it out until you are finished. With the thermostat removed, disconnect the lower radiator hose from the radiator and flush the engine with a water hose alternating from the upper hose to the lower hose until the water runs clear from both outlets. I suggest you remove the core plugs before you start the chemical flush procedure. That may enable you to verify if in fact you do have plugged coolant passages and allow you use picks and/or chisels (by hand) and a water hose to physically remove rust and scale. That may help the chemical flush to be more effective and you will have the peace of mind that the core plugs will not leak while you are on the road.
Whatever direction you take, after you are sure that your system is clean I suggest you use GM Cooling System Sealer or Bars Cooling System Conditioner. These are not stop leak additives for external leaks. They are designed to seal porosity of the cylinder heads and block. The Bars product also contains water pump lubricant, seal conditioner and rust inhibiter. I have used both products over the years and was always happy with the results.
Best of luck with this headache. Permanent rust removal from a neglected cooling system is not easy. You will probably have to perform the flush procedure several times. Please keep apprised of your progress.
I used acid as well, it really removed the scale from inside the radiator. CLR is supposedly latic acid and gluconic acid. I may have used citric acid as well. Even if the original rad doesn't cool as well, it is better to use acid in the Copper Brass than in the aluminum rad. I just installed this rad in my 70S, I plan on putting some serious warm weather miles on it. So far, it barely moves the gauge around town, back and forth to work in my 70S. It is a 2 core with 1 1/8" tubes. The good aluminum radiators require 4 core saddles. I wasn't super impressed with my Champion 3 core aluminum as far as cooling ability. https://www.ebay.ca/itm/351157989603...mis&media=COPY
interesting! I read a lot about cleaning the cooling system with acids lately. I know a lot more now. The thing however that i can't find really is how long the mixture of water and acid has to stay in the system to do its job properly.
is it a few hours,days. Maybe a week? Is it harmful to keep it too long in the engine,or is it useless to keep it in there too long because is looses its potency over time?
curious to learn what the opinions are about this.
That is "as designed". Read the link(s) I provided to you (above). I'll quote the most important:
BTW: I should point out. Your test is not identical to an installed thermostat. Your pan has no laminar flow; instead, it is static. An automotive thermostat is deigned to operate under pressure - which, you have no pressure in a warm pan of water.
Thanks for clearing that up!😊 Never knew a thermostat is controlling the minimum temperature. Always assumed it's there for controlling the maximum temperature.
The point I was trying to make was your test in a static pan of warm water does not replicate what is occurring in the car. A thermostat installed in a car operates under pressure (~15psi) in a closed system - very dissimilar to an open pan of water. The design of a thermostat's shape and the materials used to manufacture a thermostat were developed to operate under a closed pressurized system. And, to be clear, the thermostat does one thing only - it opens & closes. The radiator, water pump, fan, radiator cap & thermostat operate as a system to control/maintain cooling.
The point I was trying to make was your test in a static pan of warm water does not replicate what is occurring in the car. A thermostat installed in a car operates under pressure (~15psi) in a closed system - very dissimilar to an open pan of water. The design of a thermostat's shape and the materials used to manufacture a thermostat were developed to operate under a closed pressurized system. And, to be clear, the thermostat does one thing only - it opens & closes. The radiator, water pump, fan, radiator cap & thermostat operate as a system to control/maintain cooling.
Thanks. I now run the car without t-stat. When the system is cleaned i will install a stant 180 degrees t-stat. Next thing to check is the fan clutch. Don't really know how to perform such a check. When cold there is a slight drag. If i try hard i can make the fan 1.5 to 2 full rotations. When the engine is fully hot this drag is exactly the same. Shouldn't it get more drag or even lock up?
If i try hard i can make the fan 1.5 to 2 full rotations.
Do you mean you can grab a fan blade and "whip it" with your hand like the wheel of fortune and it will spin 1 1/2 - 2 revolutions by it self? Yes bad fan clutch.
Another way to test. With a fully warmed up engine at idle speed shut the engine off and watch the fan blades. The fan should could to an immediate stop. If the blades spin freely for several revolutions the clutch is no good.
If i try hard i can make the fan 1.5 to 2 full rotations.
Do you mean you can grab a fan blade and "whip it" with your hand like the wheel of fortune and it will spin 1 1/2 - 2 revolutions by it self? Yes bad fan clutch.
Another way to test. With a fully warmed up engine at idle speed shut the engine off and watch the fan blades. The fan should could to an immediate stop. If the blades spin freely for several revolutions the clutch is no good.
Exactly! Didn't know how to accurately explain it. Unfortunately English is not my native language.
i spin the fan like a wheel of fortune and it makes approximately 1 1/2 to 2 revolutions. Hot or cold makes no difference.
i will now do the test you recommended. I'll warm up the engine and then shut it off and see how many revolutions the fan spins freely. I'll report my findings here.
By all means do the idle shut off test but if the fan spins like the wheel of fortune the clutch is bad in my book. Here is an important note. Both my spin by hand and watch fan after shutdown test methods is only for thermostatically controlled fan clutches which where used as OEM on GM vehicles. It will not work on non-thermally controlled clutches which are used as OEM on Ford vehicles and cheap aftermarket replacements. A thermostatically controlled fan can be identified by the bi-metalic coil on the front of the clutch. Read the info in the link below for more info and please keep us appraised of your progress.
Your English is just fine. I don't know a better way to explain the spin the fan with your hand like the wheel of fortune. It has helped me diagnose bad fan clutches numerous times. It came from spinning good fan clutches so I know what a defective looks like. Just like watching the fan rotation after shut down. A key to proper diagnosis is knowing how a good part functions so you can spot a defective component.
Did the test you recommended. Got the engine fully warmed up and then shut it down. The fan didn’t stop immediately. My guess is it made about 6 to 8 full revolutions until it came to a stop.
ordered a new fan clutch at Rock auto. It’s a Hayden heavy duty unit. It can however be used in combination with the oem fan blade pitch. (2 1/2 inch).
The oxalic acid is in the cooling system for 2 days now. Drove the car 20 miles since. It makes the water a sort of fluorescent yellow. Next Sunday i’ll perform the flush process again with a fresh mixture of water and oxalic acid.
engine temp while driving currently pushes 205 degrees and 220 while idling. This is without a t-stat.
Did you check it with a digital temp gun? The gauge could be reading high. I had that happen with an aftermarket gauge. Hopefully the fan clutch makes a noticeable difference.
I was concerned when you said you were leaving the oxalic acid to sit in the engine for a week. I did an internet search and came up with the following; 3 step process (Sulfamic Acid/run for 3 hours/flush; Oxalic Acid/run for 3 hours/flush; Soda Ash/run for 3 hours/flush) and the results were impressive. I have yet to flush the Soda Ash and add the distilled water and coolant, but I know I've got a much cleaner radiator. What ever flush chemicals you use I suggest neutralizing the acid(s) with baking soda.
I still a fan of pulling the core plugs; I had a leaky core plug so I changed them all. Back of the block was caked with some kind of black mud. Took three treatments with pressure washer before water ran out clear. Never could have changed coolant enough to get that out. I highly recommend spraying out the block and changing welch plugs.
Did you check it with a digital temp gun? The gauge could be reading high. I had that happen with an aftermarket gauge. Hopefully the fan clutch makes a noticeable difference.
I did not check it with a digital temp gun. I don't have one. What i did do was putting the gauge temp sensor in a pan filled with water and brought the temp up till the water boiled. In the pan was a thermometer as well. The readings on the thermometer and the temp gauge were exactly the same from cold to boiling.
i also hope the new fan clutch will make a difference. I guess at some point the cause of this problem has to come up anyway.
I was concerned when you said you were leaving the oxalic acid to sit in the engine for a week. I did an internet search and came up with the following; 3 step process (Sulfamic Acid/run for 3 hours/flush; Oxalic Acid/run for 3 hours/flush; Soda Ash/run for 3 hours/flush) and the results were impressive. I have yet to flush the Soda Ash and add the distilled water and coolant, but I know I've got a much cleaner radiator. What ever flush chemicals you use I suggest neutralizing the acid(s) with baking soda.
I still a fan of pulling the core plugs; I had a leaky core plug so I changed them all. Back of the block was caked with some kind of black mud. Took three treatments with pressure washer before water ran out clear. Never could have changed coolant enough to get that out. I highly recommend spraying out the block and changing welch plugs.
Thanks for your time and effort to help! I appreciate it!
So,the sulfamic acid attacks the scale deposits and the oxalic acid acid attacks the rust.
what is the soda ash for? Baking soda is there to neutrolize the acids.
the welch/core plugs are the freeze plugs? Can you remove them with the engine still in the car?
There are three on each side of the block. You have to remove the starter motor, the engine mounts, and steering pump brackets. It is not as much work as it sounds and I think it is the right way to get all the crud out. You will also be replacing 50 year old (assuming the engine is original) freeze plugs that have questionable remaining life, particularly with a neglected cooling system and the use of acids to remove the rust. I wouldn't want a core plug to spring a leak on road in my car. Just saying...
Maybe i'll just pull the engine,pressure wash all the freezeplug openings and replace the plugs all together.
That seems the easiest and most thorough method here.
pulling the engine isn't that much work anyway.
if all the freeze plug openings are pressure washed it isn't necessary to pull the heads as well?
If you have a place to do it and a hoist pulling the engine is not that much more work thought it usually leads to more MAW (might as well). No the heads do not have to be removed to replace the cylinder block core plugs. There are additional core plugs in the heads that may be a lot easier to replace with the engine out. You can also clean and paint the engine too. I just thought of another MAW - install new engine mounts since they are going to be removed if you do the work in the chassis or pull the engine. Pulling the fore mentioned components, cleaning the water jackets, replacing the cylinder block core plugs, and reassembly can be done in a day if you have everything ready before you start. If you pull the engine, clean the jackets, replace the all the core plugs, prep and paint the engine count on two maybe three days...
BillK is a poster here on CO who may be able to help you out with a core plug kit. Search this site for the correct engine mount part numbers.
If all this overwhelming you can stick with removing the cylinder block drains, do the flush and see if that cleans up the internal rust condition. I hope I'm not piling it on and derailing you. To me this is the reality of owning a 50 year old classic. Some look at it as a labor of love, others look at it as labor. The choice is yours. If things start to go south you can PM me. I'll do my best to talk you off the ledge and help you out.
You have been pulling the block drain plugs when draining everything correct? I might help remove rust and scale from that area. A temp gun is cheap and a verification of the proper temp.
Another method, if you suspect the block is "crudded up" remove a threaded drain plug to inspect, then remove only the most accessible frost/welch plug with the engine in place and look inside. This will also give you a chance to see the condition of the plug. If it is "crudded up" you can pull the engine to do the work, if it is clean just install a new plug.
Dynoking;
thanks again for your assistance! I have everything necessary to pull the engine including a workshop where i can work. For me it isn’t just labor. It is labor of love. Once the cooling system is repaired my Olds is more ore less flawless. Can’t understand how the previous owner failed to properly maintain this system. Such a waste of an otherwise fine automobile.
and it is not overwhelming. With the right information,tools and parts it isn’t difficult,just a lot of work. I am a patient man🙂
Oh,forgot to mention there is one MAW. Lefthand exhaust manifold has a leaking gasket. I have a pair of gaskets already. Shouldn’t be too difficult to replace if not one ore more of the bolts snap off. Fingers crossed!
Replaced old the water/ oxalid acid with a new mixture today. To my surprise the old mixture came out and was almost clear. There was some fluorescent yellow residu though,but no crud,rustparticles or other foreign objects. Strange. Thought it would be much more contaminated. While currently driving the car it seems temperature starts to drop a bit. Except for standing still and idling than temperature starts rising rapidly.
Next friday my new fan clutch is due to arrive. I’ll keep flushing till then,install the new fan clutch and if things haven’t improved considerably at that point i’ll pull the engine and pressure wash all the coreplug holes.
Olds 307 and 403;
i did not use the block drain plugs. I disconnect the upper and lower rad hose and let the water out. In order to drain the block completely i blow air wit my compressor through the upper hose and block to let out the water out of the lower hose. Is that sufficient to drain the cooling system completely?
sugar Bear;
You know where i can find such a threaded drain plug? I think it can be very helpful to remove such a plug and inspect what’s going on behind there. But i removed the water/oxalic cid mixture today after it had been in the engine for 5 days and i came out almost clear?! Didn’t really expected to see that.
thanks again all for your interest and advice! It is appreciated..
June 17th, 2022, 08:34 AM
