A version of this gets posted every summer, but I'll throw my story out here and see what I get. About 3 years ago I swapped a 455 Olds into my 1969 Vista Cruiser. The motor is an older stock rebuild - aluminum intake, stock style water pump, and a 180F thermostat. I'm running a factory AC setup and I live in Arizona. To state the obvious - it gets HOT here. Whenever the temperature climbed above 85-90F outside (which isn't even hot), my aftermarket gauge (Stewart Warner) indicated the car would run hot. In the 230F range during stop and go traffic with the AC on. Cutting the AC helped a bit, but it'd still stay around 215-220. Open highway driving didn't help- it would still get up there with the AC on.

This summer I replaced the older 4-row brass/copper radiator for a Cold Case aluminum one. Now the car runs fine on the open highway - 60-70 mph with the AC on and it stays around 205F (tested on a 100F day). However, it still climbs to 235F if I'm idling for a while (10 mins) or in long stop-and-go driving. I cut it off at that point.

I'm taking this to mean I now have sufficient cooling capacity but a low-speed airflow issue. I replaced the fan clutch with a Hayden HD model and I have the 7 blade 19" stock fan. No difference - I still climb to 230F or so if idle for a while.

I have (what I believe) is a stock fan shroud though the fan does seem to sit deeper in the shroud than expected. I have the rubber seal on the bottom and sides of the radiator. I am missing the passenger side masticated rubber strip - but can one small piece of rubber really make that much of a difference? I'm running 50/50 antifreeze - I even brought premixed to ensure it was correct. There are no mouse nests, scorpion dens, or rattlesnakes blocking the radiator or condenser.

I've spoken to a few shops and as expected get conflicting answers. Everything from "oh that's normal these ran hot back in the day", "aluminum radiators aren't as good as the original", "put electric fans on", and "if the idiot temp light isn't on your OK".

My last thoughts are:
1. Replace the thermostat just to see if that helps. I really don't think that will do anything though. The current one is 3 years old and the car runs fine on the highway.
2. Adjust the tension spring on the Hayden HD fan clutch to get stronger lockup and therefore more airflow at low speed.
3. Check the timing? Though my mechanic (who set the timing 3 years ago) said that's highly unlikely as the timing would have to be way way off to run this hot.
4. Water pump - I really don't think this is an issue either as highway drives fine.

Any suggestions? Is this really just normal and having a gauge is making me crazy? I can see not being able to run the AC while idling on a 115F day, but I'm getting hot under much less severe conditions.

Thanks for any input!

 

The thermostat won't do anything, unless it's malfunctioning (which is unlikely). The rated temp on the thermostat is the start to open point and it is typically fully open 20 degrees above that point. So that won't do anything.

Let's talk about your radiator. How many "rows" is it? Your problem, as you mentioned, is that you need more air flow at low speeds. When you have an AC condenser in front of the radiator it's essentially a pre-heater for the air across the radiator. The more "rows" the radiator has the harder it is to get air acrossed it, meaning more pressure drop. The radiator in my Rallye 350 (which has a 455 in it) is a two row, 1.25" tube, aluminum radiator. If you look at the fins in the radiator they do NOT line up from row to row. So this creates the pressure drop. So I chose a radiator with very wide tubes and only two rows. If you have a 4 tube, 1/4" tube radiator, that is a problem. Not saying you can't make it work. But at low speed you need a LOT of air flow. I live in FL, not as hot as you, but pretty hot.

So I'd start by making the fan clutch come on sooner. I actually took a LOT of time to make sure all the sides around the fan shroud are sealed off. I doubt one piece of rubber is a problem, but as a check, go get some aluminum tape (real duct tape) and seal off all of the area around the fan shroud so the fan pulls all the air it can move across the radiator.

At low speeds you need airflow. I think a 7 blade fan is probably capable of moving enough air, but it needs to be fully engaged at idle to have a chance of moving enough air. As a test can you make it a positive drive fan and not a clutch? Again, as a test. Can that fan move enough air to accomplish what you need? I use twin electric fans and a standalone fan controller. It works well, but when both fans are on at idle, it sounds like a B-25 throttling up for launch, but the car will idle right at 165F for hours.

jerry

 

It seems like OP has a decent grasp of things. Good stuff from Jerry, however(!), I think it would be worth putting a 160* thermostat in. I know, technically it might not be a problem but for the 15 minutes & $10 worth of commitment, why not see if anything changes?

For consideration/discussion-

Are condenser fins clean & unobstructed? (Sorry, wasn’t paying attention)

Is there an efficient impeller in the water pump?

Gauge accuracy confirmed?

While my present 2 cars are both running clutch fans & shrouds, they run pretty much “on the thermostat” but that is in CT, a far cry from AZ heat & they don’t approach those coolant temps being observed. I will say, my blue car with either an aluminum or Cu radiator would run “on the fan setting” with Windstar type (actually late Tbird V8) aftermarket fan assy & Flex A Lite controller. Car can idle for hours on a 100* day and never surpass the fan setting, normally with a 180* stat. Quiet too. The reason I went to electric was unwilling to tolerate the roar of the clutch fan. Maybe clutch was bad, not sure, but I love the electric setup. Personally I wouldn’t discount an electric setup but they have to be well conceived and executed.

All this said, there technically & practically is not a problem with coolant temps being observed, BUT, I would not be comfortable with them.

​​​​​​…

 

You have a good grasp of the possible problems. And you've gotten some good guidance.

Here are two other points that may help. The first is important; the second, less so.

1. The fan blades need to be centered on the trailing edge of the fan shroud to give best air movement. Modify the shroud or change spacers on the fan to accomodate.
2. Higher anti-freeze concentrations move less heat. Unless you drive in ambient temperature below +10°F, use 25% ethylene glycol anti-freeeze if you want to gain about 8% more heat transfer ability. This percentage will protect your engine and radiator from damage down to -5°F (it turns to slush between -5 and +10 and it's not completely liquid until +10°F). Never use a lower percentage as you will not get corrosion protection; bacterial growth is also likely.

 

Good advice above...

Confirm temps with an infrared point and shoot thermometer.


50/50 anti-freeze isn't necessary in your climate, I'd drop it to 30% coolant.

Flush the system with CRC ThermoCure.

Add RedLine WaterWetter.

Figure out why the fan is too far into the shroud, if it is.

Yes a missing flap can contribute to running warm. It probably isn't all but rather part of the problem.

Thermostats can open partially instead of all the way.

Running temps ok on the highway do indicate the radiator is ok as stated.

 

You made me laugh with that as it has been one of the things I advise people to check after a co-worker had a field mouse build a nest between his radiator and condenser on a camping trip.

I would suggest checking the timing as low initial can cause the engine to run warmer.

Back when I had to run my car through emissions testing, I would decrease the initial timing and disconnect the vacuum advance for the test, and on the drive to the test facility I would see the coolant temperature go up. Then after the test, I would go around the corner, reset the timing, reconnect the vacuum advance, and the coolant temp would immediately drop back to normal. This was only a 10-15 degree change, but that may be enough to get you into a more comfortable range.

My distributor setup is a 1978 HEI with the original weights and center bar (18º mechanical advance), medium springs form a Moroso HEI recurve kit, initial set to 16º, and vacuum advance limited to 10º, and connected to manifold vacuum. The coolant runs right around thermostat temperature (180º - 190º). This is on a 350 so not 100% the same as your 455, but it might help.

 

Idle speed is often overlooked in these situations.. I learned this years ago with an old hot rod with a 455. It would hold temp all day idling at 750 rpm. I cranked the idle speed down to 500 rpm to amplify the lope of the cam. It then started getting warm idling and would eventually overheat. I tore my hair out and it dawned on me to turn the idle back up. Going from 500 to 750 rpm was a 50% gain in fan speed, it moved a **** ton more air that way and was very noticeable under the hood. This of course only applies to idling, unless you have underdrive pulleys.

 

I put a Cold Case radiator in my 75 Hurst Olds W30 (455) last year when we came back from the nationals which was 400 miles each way. The ran about 220° on the highway with the AC on. I know that is not dangerous but I just didn't like it. The Cold Case has dropped my water temp 20-25°. I used the cap that came on the radiator. A lot of good stuff has been mentioned. I did not see anybody mention the cap. One other thing to check is if the belt is tight and not slipping. After I have checked the above mentioned and don't get results. I would put a pusher fan in front of the radiator and have it come on at 180-190°.

 

My 1972 Cutlass with a 455 sat indoors for the most part for 24 years since I owned it. My brother bought it off the original owner in 1981 in Houston Texas! I painted it last year and have driven it maybe 200 miles in the last year !
Since my brother bought it it has had very little engine wise done to it. I did put a cap and wires and new plugs in it when I bought it! I replaced the radiator with a new one! Can’t remember if I put a new thermostat in it?
I had taken it out in 90 degree weather last week and went to a car show! I watched the Sun Temp and Oil gauges when driving and sitting in traffic and it never got over 200 to 205! I assume that is good! It doesn’t have an original fan/clutch but has an aluminum flex fan! Since I don’t have a long ( mileage wise) driving time on the street I do keep my eyes on the gauges! It’s the original motor/ tranny and I believe it’s all stock with the low mileage!
It does run rich and I have new Echlin Marine points/condenser/rotor to put in it! It’s pretty healthy up to about 3500 rpm’s but then it’s like the engine loses power! Could be never having been tuned up since the 1980’s! Next on my list! Just glad no overheating issues so far!
The advice above about the timing and idle speed make sense! Also, I’ve read on here if you have an OAI hood with no upper OAI air cleaner the scoops can over pressure the engine compartment so no air will flow through the radiator?? I don’t remember if you have an OAI hood?
Good luck curing this issue, it would drive me crazy!At least you have the folks above to give you good hints and advice!
OLE442

 

WearnWrals - First, what I need to say is your write-up is one of the best write-ups on CO regarding your issue. I am currently concerned with a similar issue with the 400ci in my '67 4-4-2 at idling and stop and go traffic, although I'm sure you'll get a laugh that I start getting concerned when mine reaches 205°. My set-up has a non-clutch Flex-fan, and an 18" electric pusher fan that I can toggle on/off from the cabin if needed. The pusher fan has kept it from getting >210° even above 95°. I'm thinking of putting on a non-clutch 4-blade OEM style fan just to get more air movement at idle or in stop/go traffic. I wish you the best of luck getting your operating temp down to a temp you're comfortable with!

 

Good point. However, his problem is at low speed, where this would not be a cause.

 

My 71 442 ran hot for years. I changed radiators (even a 6 row) but nothing helped
I finally put a paper towel in front of the grill and noticed it was blowing out, not pulling in. The fan clutch was too long and was causing air to backup in the shroud and blow forward. I found a short fan clutch that made the blades just barely stick out of the back of the shroud. No more overheating at idle! The car is much more fun to drive!(The fan clutch was for a 82-96 jag. XJ6) it bolted on and is short. The part # ìsNapa. 261306.I have found many fan clutches that say they will fit but are too long and put fan too deep in shroud or hit radiator.

 

Haha- good it worked! I had seen your comment while researching my problem and made sure to check!

 

Thanks for all the input so far! To answer a few questions that have been posed:
1. Radiator specs: It's a ColdCase GMA-42AB. 2 row aluminum, 1.25" tubes, 16 fins per inch. While it didn't "solve" my high temps while idling, it did improve on-highway cooling. So this radiator has increased cooling capacity compared to my previous one (whether due to size, design, or just not have mineral deposits inside - who knows!)
2. Idle speed - 710 rpm checked with a digital timing light. It's a little lower than the Service Manual recommendation of 830 rpm.
3. Attached is a picture of the fan in the fan shroud. The fan does sit a little too deep, it's not 75% inside/25% outside. The shroud looks stock to me (it has the raised spot for the radiator hose clamp) and I'm using the correct fan clutch. I suppose a shorter fan clutch standoff could be used, but there isn't a lot of room between the clutch and standoff mounting bolts as is.

Remaining things for me to do/consider:
4. I need to check the timing. I've never done that before; from what I read I need to measure initial timing with the distributor vacuum line disconnected. Does measuring total timing (vacuum line attached) provide any helpful information?
5. Add in the missing section of masticated rubber seal.
6. Switch to higher water/antifreeze mix. May provide a small benefit?
7. Consider Hayden Severe Duty Fan clutch
8. Maybe try bending the spring on the current HD fan clutch for earlier engagement. That seems tricky, since there is no way to know how much preload is really being added.

I could try the 160F thermostat- but would that really help? Since it runs fine on the highway and the temp is already above the thermostat opening temperature, I'd think a lower temp thermostat would just make it take a little longer to warm up, but once open, I'd be in the same position.

I could look into electric fans, but seems like I should be able to get the mechanical system working since everything is stock. I've read mixed things, but don't mechanical fans usually move more air than electric fans?

Thanks- Michael

 

Yes, a lower temp operating thermostat may take slightly longer but will still reach the same temp. A properly operating thermostat only controls the minimum operating temp.

Does the current thermostat open completely at its rated temperature?

 

Disconnect the vacuum line from its vacuum source, and plug the port so there isn't a vacuum leak. Check the timing at the RPM listed in the tune-up specifications.

Total timing to me is initial + mechanical. Vacuum advance is not included in that. You can easily check the timing with and without the vacuum connected to see how much vacuum advance your distributor adds. It would be much easier to do this by connecting the vacuum canister to a full manifold source so that you would have full vacuum advance at idle. If connected to a ported vacuum source, you would have to raise the engine speed to get vacuum, and there would likely be mechanical advance coming in as well, which would skew your measurements.

 

The biggest thing I see in this situation is relying on a gauge to tell you the truth without verifying the gauge.

With a healthy factory OEM 4 row cooling system, clutch fan, shroud, core support seals, good timing, and AF mixture mine runs 195° maybe 205° on a ballz out hot day.

It's been 95ish degrees with high sticky RH in my neck of the woods the last few days. Just did a cruise yesterday, 50-mile RT. Idling in traffic, it does not go above 205.

192° HD Stant, 50/50 mix regular green juice.

The point is, GM designed it to run like this. They worked fine when new. I've done nothing but maintain that engineering. I've tossed zero aftermarket fix-alls at it.

 

How would I determine if the thermostat is fully opening?

 

Exactly - if this ran fine when new, I should be able to get this running fine now.

I should mention I have verified the gauge with a cheapo IR temp gun. They correlate well and both indicate the engine is running well north of 215 once it idles for a long time, especially so if the AC is one.

Also, here are the fan/shroud pictures. I know the fan sits deeper than optimal, but does anything look like it's not a stock part leading to the stack up?

 

A 120 rpm increase is a 17% fan speed increase. Assuming my public education is ok. Thats a free thing to try.

 

All that comes to mind is placing it in water in a vessel on a stove whilst watching the water temp with an infrared thermometer and watching it open.

 

The fan should be half way in and half way out of the shroud.

 

Agree ^^^ OP is asking if anyone spots any reason it isn't half-in/half-out e.g., an incorrect component.

 

You are really only off 10° from me at 215. But you live in the desert I do not. A higher ambient temperature means a smaller temperature difference between the coolant and the surrounding air, making it harder for the radiator to dissipate heat. So anywhere you can pick up the air flow efficiency will help.

215-220° isn't over heating. You are correct you likely have an air flow issue.

One pic looks like there's excessive gap between the top plate and the radiator. But you said the seal on the rad is good. Install the missing masticated side seal.

The fan diameter looks too small to me. Or the shroud is too large. The blades should be roughly 1/2" from the shroud ID. And the blades should look line mine on the depth. Yours does look too deep to me. All of this could add up to a 10-20° loss.

The pump impeller could be off. There are a couple different impeller designs. One is better than the others at moving water and not cavitating.

Does the lower hose have the spring in it. The hose can collapse at high(er) speed...which isn't your problem.

What ° stat is in there now? Install a 192-195° HD Stat.
What is the base and vac advance timing numbers at curb idle?

Pics are of my 68 442. All stock.

 

See how much space between the fan blade trailing edges & the power steering pump hub you have to work with, as it will be a deciding factor how far back it can go. Half in / half out of the shroud may not be possible.

 

I agree with this.
I have a '66 Olds Toronado and it doesn't overheat. In fact, I thought the temp gauge wasn't working because it was 96 degrees that day. I removed the temp sensor wire. Plugged it back on and temp sensor, and the gauge went 1/2 way between "C" and "H".
One thing that I didn't see mentioned is the plastic part behind the front bumper to the radiator support. Some people calls this a "duck bill". Is that on your car ? I'm assuming all "A Bodies" used them.

The temp sensor is immersed in the coolant. The IR temp gun is not measuring the coolant ?

This is worth a try. Not only will air flow increase, but coolant flow at low RPM's will increase and could help cooling. Wouldn't you think the Oldsmobile engineers specified an RPM setting for a reason ?.

You can use a common cooking thermometer also.

 

Additional pics to scale

Power Steering pulley nut to fan blade:



3 groove A/C car Pulley to fan distance showing approximate length of the adapter the shaft and fan to pump mount.

 

From the pics the fan clutch in droldsmorland photo looks shorter.

 

I had a similar issue with my 1972 Cutlass 455 with factory A/C running R134. I ended up putting a 16” pusher electric fan on the condenser and wired it to come on when the A/C was switched on and problem solved. It never goes over 220 in traffic.

 

I got the same recommendation from a local AC shop about a pusher electric for use with R134A conversion here in Phoenix. They said the pressure with a R134A conversion gets high enough to blow out the compressor seal, and an auxiliary electric fan was mandatory in our summer temps.

 

I agree with fellow members that that may be the issue. The fan seems to sit completely inside the shroud. I'm assuming my 69 Supreme and your 69 Vista Cruiser came with the same shroud. Yours looks a bit different to me but maybe it's because its cleaned up vs mine that is driver dirty. My fan sits out more and is 1/2 and inch forward because of the aftermarket water pump ...

P.S. why does your top plate have have additional holes for securing the shroud ? My Supreme is original and doesn't have additional holes.

 

It looks like your top plate is for a 2/3 row radiator whereas his is for a 4 row radiator.

 

About the top plate: my VC was originally a 350 car with a 2/3 row radiator. The previous owner installed a 4-row radiator, but just beat the bottom saddles till it fit and mangled the 3-row top plate to seat. I replaced it with a reproduction 4-row top plate. Between the bottom saddles being abused and the riveted aluminum fixing the cracked fan shroud mounting points, the top plate sits a little higher than ideal.

I plan to go out and measure some of those features on my setup to compare. It may be that my fan standoff is too long. I'll also measure the timing and increase the idle speed.

Regarding the idle speed: seems like mine may be a bit low. My motor is also from 1970 or 1971 a but my service manual is for 1969. Are the listed idle speeds the same across these years?

 

My manual shows the ‘69 spec is 575 RPM in Drive and the 70-71-72 are 600 RPM in Drive. I’d use 600 as it’s easier to measure.

 

Here is a pic of my setup. You can see how offset the pulleys are because of the longer aftermarket aluminum water pump sitting further forward. And still you can see how far out the fan blades sit from shroud edge.


I've had my ride more than 10 years and 40,000 miles. First 5 years was with correct water pump, latter 5 years and currently is with aftermarket pump. Knock on wood, so far she has never overheated even though the cooling efficiency has been slightly compromised. No gauges on my ride just warning lights. The hot light sentinel has never even flickered on during full operation. And as you can see by condition my car is really driven. And has been track tested in brutal weather conditions.

By the way my current drive idle is 575 rpm. I literally just got back from stretching her legs and taking that pic for you. A casual 15 mile jaunt, in 80*80% temp and its about to rain...

 

Firstly- thanks for all the engagement helping to correct this problem. I did not expect as much input for a "running hot issue", since it comes up so often. A big thank you!

Ok, I went out and got some measurements, pictures attached.
1. I saw wrong, I have a 6 blade fan. Blade depth is a little over 2", but not 2.5"
2. Distance from edge of fan blade to water pump pulley nut= 3/4"
3. Distance of fan center to mounting point about = 1 5/8"
4. Fan clutch standoff length (it's part of the clutch, can't be changed) = 1 1/8"
5. Depth of shroud = 4 7/8"
6. Fan tip to shroud distance = 7/8" (the shroud is hard to mount perfectly centered, so some spots may be closer, others maybe farther)
7. Once warmed up, curb idle adjusted to 850 rpm per the manual.
8. Timing at idle (with vacuum to HEI disconnected but not plugged and carb port plugged) = 8.0 degrees

Regarding the fan depth: a) either the shroud is incorrect, b) the mangled saddles are causing the radiator to be forward a bit more than correct, or c) I need a new fan with deeper pitch to clear the shroud (this would barely work).

According to the service manual - the clutch length should be 1.5" (I measured 1 1/8" but maybe they quote to a different face) and the correct fan is a 19"/6 blade fan, which I have.

Thoughts on that initial timing measurement of 8.0 degrees? I have an engine combination not present on the manual: 455 low compression with a 4 barrel QJet. At 850 rpm, the manual specs 6 degrees for a low compression 455 with a 2 barrel, and 8 degrees for a high compression 455 with a 4 barrel.

 

Additionally, here are some IR temp gun readings across the engine bay and a picture of the temp gauge.

Unless I measured the timing wrong and need to redo it, I'm out of things to check! I suppose I could have an inefficient water pump impeller, but that pump isn't leaking so it's staying on. The thermostat could be partially opening, but I'd think highway driving would be impacted in that case.

A Hayden Severe Duty Fan might be an answer, or a deeper pitch fan. But I have throwing parts at a problem.


Passenger side radiator tank upper

Lower rad hose

Upper rad hose

Driver side radiator tank upper

Thermostat housing

Thermostat neck

Upper rad hose near thermostat

Gauge

 

It would be easy to change the initial advance to see if that makes any difference on the temperature.

 

Looks like you have the '69/70 402995 Olds fan shroud....correct for your setup.

Your top plate has the shroud attached at the top of the shroud in the two correct holes (4 row rad top plate).

Also - I seriously doubt there is any downside to changing to a factory-style closed style impeller water pump. Seems like it can only ADD fluid movement if what is on yours is a closed impeller. Sure, it entails more time and more $ but you are being "incomplete" in your diagnosis if you don't at least know what you have.

You may be able to drain the fluid, pull the lower hose and get a into the lower rad hose inlet on your pump (or put a camera/borescope up there if available).

 

Why has no one checked the fan clutch yet?

Cold: Fan spins about a half a turn with engine off and you winging it hard.
Hot: Fan spins about a blade width with engine off and you winging it hard.

If it spins freeballing, at either hot or cold, with engine off, and you winging it hard, it is dead. Rebuild or get another OEM one. If it is locked up, ever, it is dead. Same solution.

I went to Chicago this weekend. 455, redonkulus cam. Came down on a light after a ten mile cruise at 60. Ralley pac went from 40% to 50% at light. Started driving at 30 mph on next road, temp went down. Stopped for gas, spun fan. It spun 2 times and should be just a blade width. Ergo, clutch is shot and I need to fix it. Kept an eye on the temps all weekend, cruising is fine, lights were a twitch up.

If clutch is misbehaving, zip tie that mother so it doesn't spin on the clutch and go for a ride. Situation should improve. Then you know. Zero cost check.