FL442

I have a 1971 Olds 442 with the 455 and A/C. Car was mostly stock when I got it and we've been having an issue with it overheating in the Florida heat.

The radiator was a 4-core and appeared newer. Some of the other parts looked older so replaced with the following:
- GMP 130-1260p High Performance Water Pump
- Heavy Duty Hayden Clutch
- New hoses around
- Super Slat 180deg themostat
- New carb (wasn't running right with the old one)
- New heater control value
- New 18" Fan

The ram air cleaner was also missing so we replaced that. We later discovered the 18" fan was a little small and the Service Manual said it should have been 19.5 inches for the 455 with A/C. Found one and waiting to install it.

At around 40 miles per hour the car says at 190. At idle it seems to start creeping up but based on reading some of the older posts this seems like it could be due to the smaller diameter fan. At highway speeds, 60-70, the temp just keeps rising. Got up to 230 before slowing down to 40 and the temp started to come back down.

Looking for some suggestions on what to try next. The Distributor Vacuum Control Switch is currently unhooked. I think we are running the vac advance right from the manifold. It was unhooked when I got the car and we are going to look at hooking that up next.

Perhaps it is a timing issue too. Seems like some from old posts were suggesting advancing as much as you can without pinging. I saw another that said 10deg initial and 36 total. I am not sure how to set timing and don't have a light so I was going to let my mechanic do that.

Killian_Mörder

The heater control valve shouldn't affect operating temperature whatsoever.
Overheating at highway speeds automatically rules out any fan problem.
Depending on where the thermostat originated, it's remotely possible that the new one's not operating properly. If the timing's set correctly, I'd try running it without a thermostat and then see if it still overheats

don71

When I hear of a car getting hot at highway speeds makes me think of a flow restriction within the system...somewhere. Often suggested is to make sure the lower hose isn't becoming crimped or becoming squeezed shut. There should be a spring in the lower hose that aids in keeping the hose from collapsing. And yea, even new a new thermostat could be suspect.

All other tuning aspects should be confirmed from carb to timing.

FL442

The heater control valve looked to be leaking. I was just one of the parts replaced.

The car will keep getting hotter at idle, but goes back down once you start driving lower speeds. That is why I was think the smaller fan might be an issue, recirculating hotter air instead. Will try without the thermostat.

The lower hose was a ACDelco Professional Molded hose (24027L). It supposedly has built in support and I was told it didn't need a spring.

Don71, what have you seen regarding timing?

FL442

Also forgot to post we did switch to pertronix and put in a new coil. Replaced the rad cap with a new 16lb.

Sugar Bear

Overheating on the highway is classic radiator restriction, the airflow is adequate because of the speed but the rad can't dissipate the heat. Look closely at the external fins for blockage, the internal tube ends through the fill neck and shoot the rad with an infrared looking for cool spots indicating blockage. After my rant
​​​​about the rad it could be the stat not opening completely as others mentioned, I've seen a few defective new ones.

About the spring in the lower hose, get the car hot and rev the engine looking for any sign of collapse.

Any chance of using a remote camera to watch the lower hose under highway conditions?

Good luck!!!

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Killian_Mörder

An endoscope is also usefull, after draining the system. With that, it's possible to detect impurity scale and calcium deposits, the latter caused by hard water use. Once a tube gets totally blocked, flushing will no longer help. In that case, tank removal would be necessary and the blockage to be mechanically freed.
If there's head gasket damage, you could identify it, through running the engine while the thermostat's out. Then, look down the filler, in order to see if bubbles show up or not

Ozzie

I had a similar problem with my 1965 442 in the S. Louisiana summer. After trying everything I could think of, I removed the thermostat and blocked the by-pass. That made a noticeable improvement.

classicmuscle442

When checking lower hose make sure its hot, can make a spring out of a metal coat hangar bent around a shovel handle.
Make sure aftermarket water pump is set up to turn in right direction.

FL442

New water pump is clockwise rotation and should be fine. Went with that unit as others commented it worked good with their Olds.

FL442

Got the car up to temp and when reving the engine did not notice any collapsing of the lower hose. Car is an A/C car and there is a cooler in front of the rad. Checked the files from the previous owner and found that radiator was replaced in 2005 but only has like 4k miles on it. He had lots of notes and invoices in the file. I can see he had it periodically flushed. Again, outside of the areas I can see the radiator appears in good shape. With engine stopped I shot the temp of various spots from the inside and didn't find any noticeable cool spots.

Has anyone had any issues running without the distributor vacuum control switch hooked up?

classicmuscle442

See u have petronix, what is your timing set at, are you using timed or manifold vacuum? Nice looking car!

Sugar Bear

Shooting rad temps with the car running and while in upper temp range will be much more conclusive data. If there are cool spots the rad is blocked, if not we know it isn't.

About the hose collapsing, if no access to a remote camera you could use an old hose with sections of pipe in it temporarily. A member suggested making a spring by winding heavy rigid wire around a tool handle, that is a good idea as a test.

Keep up with the diagnostics you'll find it.

Nice work and good luck!!!

rustyroger

Classic symptoms of a partially plugged radiator. Yours is 16 years old if I read your posts correctly. If it has stood dry for a long time it might well be internally corroded. Well there's an easy cure for that, several good radiator shops around Dallas who car recore it for you last time I spent much time there.

Roger.

rickman

Sorry, Just reread your post and saw you already changed the clutch. Wow, short term memory and unable to comprehend...whats next?

FL442

Mechanic said timing was around 8-10 initial, and 32 total. I believe it was manifold vacuum but forgot to ask.

FL442

We actually tried a couple of clutches to make sure the new one wasn't bad. Have the heavy duty one in there now but it hasn't really helped.

FL442

I don't have a remote camera. Will see if I can find or borrow one.

One thing. At 40 to 45 mph I can run all day an have no issues with it overheating. If its hot, I cruise at that speed and it comes down. If that radiator was blocked, would it still do that? I am going to heat it up an check the temps at each hose next.

FL442

Temps at the hoses were reading around 165 while the t-stat showed 190-195. Sides of the rad were in 180s. Drivers side was always seemed hotter. Top of the thermostat housing was around 200.

Sugar Bear

If the radiator was blocked would it still do that? Yes.

​Temp shoot various parts of the radiator core,/fins that is where the cool spots will show up if any.

Put a piece of electrical tape on the thermostat housing when shooting the temp see if it changes the reading. It is something to do with IR thermometers and emissivity which can make the IR reading incorrect.
​​​​I cannot explain it, I've just learned of it on another site working on an overheat problem.

Fun71

Yep, black will give you the most accurate temperature when using an infrared thermometer (flat black is best). We have a FLIR camera at work that has emissivity compensation capability for different colored materials, but a light coat of flat black paint to make it a black body radiator (1.0 emissivity) takes all the error out of the equation.

gs72

I was having high temp issues in warm weather. 72 Cutlass S 455, Noticed the radiator was leaking. Replaced it with a Cold Case aluminum radiator and problem solved. I used to get a slight ping at cruise speed tip in throttle. Its gone now. Car runs like a champ. Highly reccomend Cold Case radiators.

Fun71

This is an area where new doesn't always mean better. Some aftermarket radiators have fewer tubes per row and a lower fin-per-inch count than the factory radiators. There have been many folks who replaced a factory 2 row radiator with an aftermarket 3 row and had worse cooling than before.
Can you measure how many fins-per-inch and number of tubes your radiator has?

69HO43

I'd get the timing situation checked out too. It seems odd that at 40mph, it seems to do fine, but when revved to 70 mph, it's having troubles. You might have enough vacuum advance around town, but maybe not enough total mechanical advance. Just something to check. At 70 mph, you shouldn't be relying on your fan to do anything anyway.

Does it run ok at higher speeds? Thinking maybe a lean condition could cause a little overheating as well. Float bowl set right? Just thinking out loud. May be just fine.

As mentioned, this could be an air blocking issue where there is air restrictions across the fins. What about the condenser? You said it's an A/C car? Or no? Or as mentioned too, the hose could be collapsing. Professional series doesn't mean squat as far as the hose as it's more marketing term than quality description. Can you use your hand to squeeze the lower rad hose? (do that when it's cold) If that is the case, it can collapse at higher highway speeds, regardless of who told you that you don't need a spring. Put a spring in it if needed. OTOH, If it's so stiff that you have a problem squeezing the hose down in the middle, then I would say your hose may be stiff enough to resist collapse. I guess my experiences were always making sure to have a spring in the bottom hose. I take no chances on that.

Just some thoughts. Could be wrong.

Fun71

This info has me thinking about a similar experience I had with my car.
Instead of telling us what MPH, can you give the engine RPM? On my car, I found that at 70+ MPH on the highway, the engine was at around 3400 RPM and apparently with the AC on and 110+ ambient temps, the engine was generating more heat than the radiator could dissipate and the temps started climbing above 210F. If I slowed down so the engine was just under 3000 RPM, I could drive all day at 190F. This was with a very good radiator, a high efficiency 4 row core made into my 3 row end tanks by a local radiator shop. A that time my car had short 245-60-14 tires (24"-ish tall) which made the 3.23 rear gears seem even lower, which caused the engine to generate more heat than the radiator could keep up with during the blistering summer temps.

My442

If the advance springs are weak, they allow too much advance at higher RPMs, resulting in advanced timing and overheating.

I chased a problem like this, and found out that total timing is critical to running temps.

BTW - an aluminum radiator dropped my temps from 205/210 to 175/180 no matter how hot it is outside.

sherlock1212

Had the same thing after the motor was rebuilt.They had to install a higher thermostat I believe it was a 210 this allowed the temperature to go higher so the rad had more time to cool the water seemed to work good after that

JohnnyBs68S

This makes no sense. A hotter thermostat prevents water from circulating through the radiator longer until the engine reaches an even higher temp. This cannot possibly allow the radiator "more time to cool the water". Once the thermostat opens, a higher temp thermostat will restrict flow more than a lower temp thermostat (that's how it makes it run hotter), which can't possibly cool the engine better. I suspect that you had a marginal cooling situation that resulted in large temperature fluctuations under varying cooling conditions, and putting in a higher temp thermostat simply reduced those temperature fluctuations (by clipping off the "valleys" of the variations). That's not the same as cooling the engine better.

The symptoms of cooling fine at 40-45 MPH and thermal runaway at 70 MPH indicates either the timing is advancing too much at higher RPMs and generating more heat, or the rear gear ratio is too high for the configuration (A/C condenser restricts airflow through radiator). This is why the factory limited the rear-gear ratios on A/C equipped cars, or didn't offer A/C on high-geared performance models. Do you know what your rear gear ratio is (and your trans in case its been swapped to an OD)? If timing checks out and your rear gear isn't in the high 3s or 4s, then the radiator is likely restricting the flow of coolant.

I'd still install a spring in the lower radiator hose. Running without one is inviting trouble. But if you want to fabricate your own, don't use steel wire which will corrode, use stainless or aluminum instead.

70W-32

Are you running a fan shroud, and the air deflector under the core support?

FL442

Car runs good at higher speeds. It was still pulling good at 70+ before I slowed down. Car is an A/C car. Sometimes only a small chirp if I mat it off the line, but soon after it really kicks in an pulls. I would have expected a little more immediately.

I can squeeze the lower hose. Will look to add a spring next.

FL442

Yes to both. Fan shroud was is an original part so there is more than an inch of space between it and the 18" fan blade tips. This is why I am going to the 19.5" fan as service manual said. Folks at Parts Place told me the 18" fan was right for my car. Others have suggested they too had problems with the smaller ran.

FL442

Spring seems to be cheap and easy thing to try so I'm adding it to the to do list. I don't know the gear ratio but the transmission is a TH400. I've had other cars with higher rear ratios and it doesn't feel like that. Going to check the RPM at various speeds. At 70mph I think it was around 3k RPM. Honestly not sure how accurate the speedo is at higher speeds. Car has allegedly been up to 90 and felt like it had more. I've been looking for ones of those speed signs on the highway to check.

FL442

Thanks for the tip on the advance spring. Going to add that to the list to check.

I realize a new aluminum radiator would help but consider that my last option because of the expense. Preparing myself for it nonetheless.

OLDSter Ralph

Johnny is correct about a higher temp thermostat ! The temperature rating of a thermostat is when the water next to it reaches a certain temp and allows coolant to flow from the engine block. If it cooled more with a the higher temp thermostat, you most likely had a BAD (defective) thermostat.
Aluminum wire will corrode. Get a radiator hose spring from a junkyard.

FL442

I was a little off earlier on the RPMs.

40mph: 2200
45mph: 2500
60mph: 3400
70mph: 4000
80mph: 4500

Fun71

OK, so your engine starts to heat up after some amount of time running at 3400 to 4000 RPM in fairly warm ambient temperatures, but it drops down to normal if you bring the engine speed down to around 2200 RPM.

​​​​​​​Sounds like a cooling system capacity issue to me, as in your radiator can't dissipate the amount of heat the engine is generating at 3400+ RPM.

matt69olds

Are all the shrouds and baffles present around the radiator? There are tar paper-like shrouds the clip to the radiator top plate and then to the core support. One on each side. There are also rubber insulators that clip to the core support to take up the space between the radiator tanks and the core support. There are also shrouds around the bumper brackets, all designed to funnel air thru the radiator.

rfpowerdude

I have found that those GMB pumps manufacturer went to crap and the impeller slips on the shaft on some of them. Luck of the draw. I had this exact problem on my 455 and went through everything first before the pump and no improvement. I then said, what the hell, and replaced the GMB with a stock replacement iron pump and the problem went away.

Just another possibility that was not specifically mentioned.

My442

Another potential root cause: The impeller on the water pump is slipping at higher RPM.

Most of the aftermarket water pumps have stamped impellers.

rfpowerdude

Looks like we may have been typing the same thing at the same time My442!

OP, may be the last thing you can try.