WHY? Engine temp runs cool in traffic, but overheats on highways?

[69hurstolds]

Staggered core radiators are more efficient than the old one behind the other rads. So they give up their heat quicker. However, you have considerably less load on the engine around town so you may be getting enough flow. Sounds like the fan clutch is working the way it should. May not be perfect, but if it was slipping, you'd overheat in town and have no real effect on highway speeds. You're not going fast enough at 55 or so to get pressure build up under the hood stopping air flow through the rad, so I doubt it's air flow issues.

Everything is full and burped, right and coolant volume is correct? I'm assuming so.

Not sure how long your radiator has sat, but corrosion of the solder joint and copper alloy corrosion will occur no matter what you do if a system sits for years. Corrosion in the block can and will migrate.

Some people tend to think that if the coolant is green/red or whatever color, it can sit indefinitely in the system. But with no flow, that stuff will stratify sitting for years. Corrosion can and does happen in a stagnant system. A short time may not be an issue, but several years may cause issues.

I don't think it's the pump unless there is something severely wrong with clearances or something physically hosed with the pump. Assuming T-stat operating right as well.

Oh, here is an important question......DO YOU HAVE AN ANTI-COLLAPSE SPRING IN THE LOWER RADIATOR HOSE? New hoses don't always need it because some brand's hose walls are pretty stiff, but as they age or if you get some of the cheaper hoses out there, they perform ok at low speeds, but at higher RPM they have a tendency to suck the hose flat, or at least restrict flow to the engine. Which means you restrict flow everywhere. No heat transfer....guess what happens?

There's not much to the system, so it shouldn't be a huge ordeal to pinpoint what the issue is.

I know this is going to sound really stupid out in Arizona, but next time you are driving on the highway and it's heating up, turn on the heater and see if that doesn't help cool things down for a bit. Wouldn't leave it on for a long time cuz you'll turn yourself into BBQ. If you get a drop in temps, then it's a cooling capacity issue, pointing to most likely a clogging radiator or crud build up in the block or both.

 

[Streetbu]

I had a similar issue. Too much timing will cause it, also I had installed "pretty" aluminum pullies on the engine and they ended up being smaller diameter on the water pump. They slowed the pump too much and I wasn't getting enough coolant flow thru the radiator....

 

[azmusclecar]

To put everything out there:
I never had the chance to take the car out on the road until now. The car was NOT roadworthy until now.
I bought the car with stock components and MOST of them were on the car.

I had a water pump leak upon purchase, so I replaced the water pump.
I put new belts on the engine.
New radiator hoses.
New thermostat 180

I just had my QJet rebuilt by Ken at Everyday Performance. It is running extremely well!! KUDUS KEN!

I am running a coolant overflow tank
I have a new 16 lb radiator cap.

I have not changed timing
I regapped NEW plugs to .45

I made sure coolant system was FULL and didn't have an air gap in it.

Now maybe from that this can help you to help me..

Are we still at the 40 year old radiator or is it the fan clutch?

I do NOT have $400 for a radiator and clutch. I am NOT buying cheap parts but I cannot afford to buy top shelf.
So please keep the suggestions to a reasonable cost.


😎👍🙂

I am taking a break from the car this weekend and will attack it next week.

Let's ALL have a blessed Memorial Day Weekend and remember ALL, ALL that have served and ARE serving.

With the car just receiving it's first true shakedown run since purchase, I have plenty of issues to address that could not be known
until I got it out and tested it.

I am pleased with it's overall performance but I want to address the major issues first, like the cooling and the other ones do not
truly affect safety or reliability.

Happy Memorial Day Weekend. May God bless our military.

 

[azmusclecar]

Staggered core radiators are more efficient than the old one behind the other rads. So they give up their heat quicker. However, you have considerably less load on the engine around town so you may be getting enough flow. Sounds like the fan clutch is working the way it should. May not be perfect, but if it was slipping, you'd overheat in town and have no real effect on highway speeds. You're not going fast enough at 55 or so to get pressure build up under the hood stopping air flow through the rad, so I doubt it's air flow issues.



I know this is going to sound really stupid out in Arizona, but next time you are driving on the highway and it's heating up, turn on the heater and see if that doesn't help cool things down for a bit. Wouldn't leave it on for a long time cuz you'll turn yourself into BBQ. If you get a drop in temps, then it's a cooling capacity issue, pointing to most likely a clogging radiator or crud build up in the block or both.

I learned this little trick long ago to turn the heater on to act like a second radiator to cool coolant temps down. I did run the heater with the setting
at hot to allow max cooling. It's hard to see much degree difference on these small gauges so I would say the lowering of the temp was maybe
a few degrees.

I know my new lower radiator hose does NOT have a spring in it. It does seem to have the structural integrity built in but we never know.

And by the way, nothing sounds stupid in Arizona so don't think we are offended with suggestions. We usually send most bad suggestions to Washington DC and then wonder why later.......but this is not about politics, it's an attempt at humor sad as it is.

 

[azmusclecar]

I had a similar issue. Too much timing will cause it, also I had installed "pretty" aluminum pullies on the engine and they ended up being smaller diameter on the water pump. They slowed the pump too much and I wasn't getting enough coolant flow thru the radiator....

I did NOT change out any pulleys..........all stock. I even cleaned the grooves to make max friction with the new belt.

 

[azmusclecar]

Not sure how long your radiator has sat, but corrosion of the solder joint and copper alloy corrosion will occur no matter what you do if a system sits for years. Corrosion in the block can and will migrate.

The radiator which I had out of the car looks to be original. I have NOT found any leaks bowever there is natural build up of corrosion on the
inside. I made sure when I had it out that there were minimal fins bent on the cooling surface.

 

[olds307 and 403]

It would bet it is the rad. A bad clutch will show up a low speeds and doesn't do squat at highway speeds. Get a 2" aluminum with 1" cores. https://www.championradiators.com/American-Eagle-Oldsmobile-Cutlass-radiator-shroud-1978-1987 The Champion rad should be in your price range. As I said 210 isn't the end of the world but you guys still have the hottest weather to come, correct?

 

[azmusclecar]

When my fan clutch was bad it only over heated in traffic I would say cooling system not flowing or radiator to small does it have a 3 core radiator or a 2 core

Stock radiator.....(by the way I love the wheels on your H/O) Just ordered a set myself) but I dont't want to hijack my own thread🙂😆😀

 

[DRIVEN]

I'd put my money on the radiator. 40 years of calcification is starting to show. You can probably find cool spots using an infrared temp gun.
Rockauto has a Spectra listing for HD cooling for $84. I put a standard Spectra in my '79 about 10 years ago and it's held up fine. It's obviously not stock in construction or appearance but those aluminum cores with tighter fin count are quite a bit more efficient.
If you do replace the radiator it may be a good idea to thoroughly flush the engine while the hoses are disconnected. Careful not to get too aggressive through the heater core or you'll be replacing it next.
Good luck and be sure to let us know how it all works out.

 

[69hurstolds]

I do NOT have $400 for a radiator and clutch. I am NOT buying cheap parts but I cannot afford to buy top shelf.
So please keep the suggestions to a reasonable cost.

Sorry, but that's not our job. When we (collectively) barge in and offer our varied in value advice, we are like Congress....we're good at spending YOUR money.

We volunteer free advice to help YOU fix YOUR stuff. But it's up to you to decide whether you want first listen to any of our advice, find the root cause, decide on a fix plan, and then to spend $$, how much, and where, or if you want to farm it out or do it yourself. I get that you don't want to waste money and put it where it will get you the most bang for the buck, hell we all want that. Not saying these are your fixes, but if a new radiator and clutch ends up being what you need to fix your issues and it costs $400, then that's what it is. You wanna play, you gotta pay.

Case in point, without naming names, a 442 on here was dismantled to the ground, then rust repair was done by the owner and the project was labor intensive, but the body work was totally a work of art. More than I'd personally want to chew, for sure. Couldn't even say how much money/time/effort was poured into the project. Paint job was done and it was color sanded/buffed and looked absolutely awesome. I offered up a complete NOS set of 442 stripes and a header panel stand up emblem at a discounted price just so the car would look as factory as possible, at least cosmetically. Had the deal going, everything was packed up and ready to ship, just was waiting for the payment, then he backs out, saying he could get the factory stripes repro'ed for cheaper (that was some BS - haven't seen any correct repros of those stripes, have you?). So what happens? He puts one of those cheap no color backed gold stripe kits on it. And they weren't even put on correctly. IMO, it made the entire car look like dogshiit at that point. It was over for me. Hope he's still enjoying the car because it truly was a labor of love there. My point is, cheaping out after spending all that time and money to try and save a buck or two sometimes ruins the entire project. Ain't my car or my money, cuz you're the one that has to live with it. Just something to consider. There's some things you just can't be cheap with.

You could, say, find a reputable radiator shop locally, if you have one, that can inspect and maybe boil it out or repair, or what not and likely come out with a just like new radiator for less than a new one. Who knows. But again, that's your call. So far it seems you've been doing well into deciding your cash flows to the car. Don't worry about the costs just yet. Get to the root of the problem and then do your cost analysis to fix any problems. It could be simple, cheap, or even free to fix.

But you didn't answer this question yet.....do you have an anti-collapse spring installed in your lower radiator hose? Again, not saying this is your issue, I'm just curious.