Took my '72 U code Supreme to work yesterday and today and noticed temp was climbing up higher than normal when sitting still. I was stuck in traffic a bit yesterday and noticed she climbed to around 215-220. Not earth shattering, but still hotter than usual. (normally around 195-200) It cooled down once I was rolling again, but not right away. Today after sitting at a couple lights it did the same thing. She was fine on the way to work both days, (cooler mornings and didn't have any lengthy stops), but on the way home is when it got a little hot. This is the first time its done it. Every other SE VA summer since I've had it, it's been fine.

Out of curiosity, I checked the coolant level in the radiator when it cooled off, and it was a little low, but the reservoir was completely full. When I took the cap off the reservoir, I noticed the pickup tube was missing.



This tells me that the coolant wasn't getting sucked back into the radiator, causing the low level in the radiator, which is why the temps are climbing when sitting still.

I was able to fish the pickup tube out of the reservoir and re attached it to the cap with a hose clamp. I didn't add any coolant to the radiator because logic would dictate that the reservoir will bring the radiator level back up to normal.

So that's where I am...is my train of thought on the right track or completely derailed?

 

I believe your logic is correct as stated. None-the-less, it's doubtful any harm would come of adding some coolant (sorta like a quick siphon to gitter moving maybe?).

 

Your theory makes sense and is probably correct. Look on the radiator tank for a full line, the radiator may not be low as crossflow radiators don't get filled to the top. I'd fill the radiator and the reservoir both to the full line vs. waiting to see if the coolant gets pulled back in from the overflow tank. If it gets pulled back in then the reservoir will be low anyway.

 

^^x2^^ What Jeff said!

 

I can't add anymore coolant to the reservoir...it's completely full.

 

I understand that crossflow radiators dont get filled to the top, but I'm pretty sure the level in mine is lower than normal right now. (See pic above).

 

It looks normal in the image.

QUESTION: You growing algae in your radiator? That's some awfully darn green coolant.

 

Norm, the pic is deceiving....the level is actually about 4" below the rad neck. As far as the green coolant it's just Prestone 50/50. Fresh out of the bottle about a month ago when I changed my intake gaskets.

 

Here's a thought. Fill radiator. Disconnect overflow tube at the coolant reservoir and fix the overflow tube to side of radiator (rubber band, whatever), cruise about a couple days noting changes in radiator coolant level - it should level off at it's happy place. Then, reattach the puke (overflow) tube back up to the reservoir.

 

It should level off after the first drive without doing anything.

 

That's exactly what I'm thinking...the coolant level in the radiator should return to normal, correct?

 

That's exactly how I do it to be honest. That's how it would be done in a car w/o a return overflow line.

 

^^Exactly^^

 

Would I actually have to drive it, or just start it up and let it warm up to temperature, and then shut it down?
Also, I think I'm going to have to transfer some of the coolant from the reservoir to the radiator. As I said, the reservoir is completely full, so there's literally no room for anymore. I'm thinking if I don't empty the reservoir, then once it warms up, all the excess will get dumped.

 

Do you have the correct radiator cap for a 2-way system, its not the same as one used for the closed(no return jug) system.

Best thing to do, is refill your radiator with the coolant thats in your recovery jug, leave only enough coolant in the jug to cover the bottom of the pick-up,
seal it up and drive it to get the system hot, check overflow level,
then park it and let it cool(1/2 a day), check levels, see if overflow returned fluid to radiator.

 

I transferred enough coolant to bring the rad back up to the proper level, and my reservoir is still just over 1/2 full. That's about where I've always kept it. As far as the cap, here's the one I have.

It does say it's for a closed system, and it's never given me any issues in 6 years, so I'm guessing it's correct.

 

Your theory seems spot on.
But you can always go straight water for the summer and ditch the antifreeze

 

I'm pretty sure closed coolant systems w/ an overflow recovery tank are supposed to run with the radiator full to the neck. Eventually, all air is purged from the radiator into the overflow tank when warming up, then sucking pure liquid back into the radiator when cooling off (assuming the tube it still attached). The only reason the radiators on cars that didn't originally come w/ an overflow recovery tank have a "FULL" level well below the neck was to allow room for expansion and avoid puking out antifreeze on the ground the first time it warms up after filling. Personally, on cars w/ overflow recovery tanks, I fill the radiator up to the neck cold, put on the cap, and then fill the recovery tank to the "full cold" mark. After a few hot/cold cycles, top off the recovery tank until it is at "full cold" w/ a cold engine.

 

So I drove it to an appt today and when I parked, I let it idle and watched the gauge. After about a minute or so, it climbed to about 210. I checked the reservoir level and it didn't change from when I transferred some coolant into the radiator the other day. I thought for sure I had it figured out, but apparently not.

So....do I dig deeper into the issue, or just let it be? And, is 210-220 abnormal for temperature when idling? On the highway it's still around 195.

 

Have you checked your fan clutch? It sounds like it might be failing if your temp is hot idling but fine on the highway.

 

Yup yup...it's good.

 

👍

Well, that is a curious problem. Good luck.

 

If you started that warm-up cycle w/ the radiator at the "FULL" level (inches below the neck), then all warming up did was push the air out of the radiator and into the recovery tank, where it bubbled away to the atmosphere. The recovery tank won't show the total system coolant level accurately until all the air has been purged between the radiator and the recovery tank. It may take a few temp cycles to purge all the air, just keep the recovery tank from getting sucked dry when the engine cools otherwise that will pull air back into the radiator. Expect the recovery tank level to drop after cooling until all the air has been purged out of the radiator.

IMO, its on the warm side, but idling in hot temperatures is towards the extreme conditions "corner" where the system is designed to handle. If there is still air in the radiator under these conditions (apparent by the fact the level in your recovery tank had not changed after one warm-up), getting all the air purged out only helps carry the heat from the engine to the radiator where it is dissipated. My advice is to get a few warm/cool cycles under your belt and when you see the recovery tank level start to change, keep it from running dry during cool-down and it should eventually stabilize. Recheck your hot idle temp and let us know if it gets any better.

 

I think it's already getting better. After I left my appt I ran a couple errands and while sitting at a couple lengthy lights, the temp gauge barely moved. I'm gonna just keep an eye on it for now.

 

Dave - You have an upgraded cam in your car don't you and IIRC, wasn't your car ran at the tracks (or somewhere). Anyways, my point is you might expect yours to run a tad warmer; but, I think you're fine.

 

One thing that is often overlooked with warm/hot idle temps is idle speed. If your idling in gear at 500 rpm and increase the idle to 750, you have increased your fan speed by 50%. Of course more fan speed gives more CFM. Even a small difference from 500 to 600 may seem like nothing but it's still 20% increase in fan speed. This of course only applies to mechanical fans.

I learned this the hard way with an Buick i had. It was a four speed car with a cam in it. At 700 rpm it would idle cool and behave. I lowered the idle speed to 500 so it wouid really lope but it suddenly got hot idling.. it took me a minute to figure it out but once i increased the idle speed the problem went away.

 

I just checked the level in the reservoir and it's definitely gone down. I'm just below 1/2 full now.

 

Check oil dip stick for water intrusion

 

Normal behavior as the air gets purged. Just don't let the recovery tank go below "Full Cold" when the engine is cold. As long as there are no leaks or blown head gaskets as leftlaneonly suggested, it will stabilize. Patience.

 

Because there will be little to no head space in the radiator once everything levels out. As mentioned refill the reservoir to the cold level mark once the engine cools.

 

95 deg outside today and she barely broke 200. I'd say I'm good.

 

You weren't driving fast enough!!!

 

Lol Norm...you're correct. I did, however, hold a steady 65-70 mph.

 

Well, it seems my woes still exist. I was in stop and go traffic at a light for about 10 minutes today and my temp climbed to around 210-220. I checked the fan clutch when I got home while the engine was still hot, and it spun maybe 3-4 times. I let it cool off and checked it again..maybe 1/6 of a turn. I'm going to check my coolant level in the radiator and rhe reservoir, but in the meantime, from what I've described, does it sound like a bad fan clutch?

UPDATE: . Coolant level in the radiator and the reservoir are good. Radiator is about 2" below the neck and the reservoir is about 1" above the "add" mark.

 

Just a thought, you said you replaced the intake gaskets, have you checked for leaks. Not fluid leaks but air, this could cause a lean condition and hence overheating.

 

It would "appear" the fan clutch is working as you'd expect I believe. You have a thermal fan clutch w/ the bi-metal circular labyrinth (e.g. looks similar to a choke coil). As the engine heats up (or remains hot), the spring/coil expands & silicone fluid flows & engages the fan e.g. the fan should rotate more than if the engine was cool. As the engine cools, the spring/coil contracts/relaxes & disengages the fan - fewer rotations of the fan.

 

That would be detected as a vacuum leak, correct? If so, then I can safely say I have no vacuum leaks.

 

Can anyone else side with Norm on this?

 

Have you verified your idle speed is correct?

 

It's set at around 950 in gear