Strange overheating issue...

Ok, I'm at a loss here. I have no idea why my Riviera is doing what it is doing. Maybe it's a common issue and I don't know about it?

97 Buick Riviera. 3800 SC Series 2.

Anyways, it's overheating. Simple? Not so much. Not only is it overheating, it's pushing all it's coolant into the overflow and not circulating it through the engine. Once it's shut off, about half the coolant will make it's way back into the radiator. But not all of it. I've used the bleeder valve and sometimes it'll act bled, and others you can leave it open and nothing'll come out but steam... Radiator cap and upper hose stay cool to the touch. I've never run into anything like that before.

So what's been replaced?
radiator at some point, but not by me, and not within the past couple years
Water pump & belt
radiator cap
thermostat

Using a cooling system pressure tester, it'll hold 16 pounds forever. Well, at least 20 minutes and I gave up on it. Cap tests properly also.

Coolant is green with no evidence of contamination.

What is your guess?

TIA!

Did this just start randomly or did something lead up to it? I want to say air in the system but then you have to wonder how that air got there. Have you checked for exhaust gases?

manofmany wrote:

Did this just start randomly or did something lead up to it? I want to say air in the system but then you have to wonder how that air got there. Have you checked for exhaust gases?

I got the car with a bad steering rack and a leaky water pump. I never drove it. I fixed the issues it had, and it will idle all day long and be fine. But drive it, and it overheats after 5 minutes...

I was kind of thinking that, too... But I have no idea how to get the rest of the air out of the system. I even filled the block when I had the thermostat out. And then I "Pressure Filled" the radiator and upper hose by cupping my hand over the reservoir to make an air-tight fit and used my compressor to pressurize the system til coolant started coming out of the bleeder... Best I could do to get as much air out as possible before closing the system and starting the car. And then once the t-stat opened, I was revving the motor with the bleeder open til it streamed steady. Closed it. And then 30 seconds later, it would be all steam again...

But what explains ALL the coolant being pushed into the overflow instead of circulating through the engine?

Just a quick question, but have you noticed pressure in the system after it cools down? Hard coolant lines, or pressure when removing the cap or opening the bleeder? Sounds like the combustion chamber is pressurizing the coolant into the overflow tank.

If the system was drained and filled properly and is still doing this, I would advise a leak down test. This sounds like an issue I just had on a 3400 we had bought. It never did overheat but temps were all over the place. I ended up replacing the head gaskets.

how do you know the new thermo is any good? I ask because i bought a brand new Stant that turned out to be bad.

Well, here is my 4 cents, and unfortunately it doesn't contain a magic answer... even though I have the exact same model.

I have to say that everything that everyone has posted is quite legitimate. My only input would be that you have done all the 'normal' stuff, and even if air was trapped in the typical spot in the heater core, I don't think it would matter at this time of year. If you want to be sure, park or lift the car so that the nose is about 15 degrees high and run it for 20 or 30 minutes while you purge air out of the filler neck on the radiator.

The most intriguing thing is that you said, "it will idle all day long and be fine. But drive it, and it overheats after 5 minutes... "

I don't think that could happen even if you had a bad thermostat or a big air problem. Idling is generally the worst time for heating up - that's when the fans have to come on... With all the contradictory evidence, I tend to think that you've either got a really wiggy stat, or else the impeller on the new water pump is spinning free. That last part may sound out there, but I myself had a new Delco pump that lasted all of 5,000 miles before the seal let go...

I would start with the elevated air burp, re-test the pressure for more than 20 minutes, and then replace the stat since it is cheap and easy with only the rubber seal to deal with.

To quote Mission: Impossible, "Good luck, Jim!"

After reading this, my first impression is you have a bad water pump. The impeller is spinning on the shaft while under a load.
At idle it may be moving enough fluid to keep the engine cool but once under way the impeller isn't keeping up and causing the problem your experiencing.

They are cheap enough to replace and also do a leakdown test on the engine just to be sure you aren't getting any hot gasses from the exhaust into the engine, But I'm still going to bet on the water pump as being your primary problem.
Without proper flow the hot coolant will regurgitate into your overflow tank after getting the engine hot and then coming to a stop.

Where u Been "B"

Rickw wrote:

After reading this, my first impression is you have a bad water pump. The impeller is spinning on the shaft while under a load.
At idle it may be moving enough fluid to keep the engine cool but once under way the impeller isn't keeping up and causing the problem your experiencing.

They are cheap enough to replace and also do a leakdown test on the engine just to be sure you aren't getting any hot gasses from the exhaust into the engine, But I'm still going to bet on the water pump as being your primary problem.
Without proper flow the hot coolant will regurgitate into your overflow tank after getting the engine hot and then coming to a stop.

From the sounds of it, he's already replaced the water pump as it was leaking.

After re-reading your description of the problem, you mention that after overheating or while overheating the upper radiator and hose are cool to the touch.
That is telling you that the thermostat is not opening.
The solution to the problem may be simpler and cheaper than thought.
Even though you have changed out the thermostat and water pump, etc. I would put a new thermostat and rubber seal in it to start. That upper hose should be hot once the thermostat even starts to open. Must not be opening.

The water pump impeller issue is still a real possibility as I have seen new ones bad out of the box.
Especially now adays when everything is made overseas with poor quality control.

But start with a thermostat replacement, I put a Safety-Stat in mine. They are a bit more expensive but when they fail, they will fail in the full open position by design so you won't overheat your engine. Ask for one at your local auto parts store. Not sure if it is labeled as Safety-Stat or just Fail Safe. You can ask the guru at the parts store, I highly recommend it. They are made to better standards as well as having the fail safe feature.
Rick

A little off-topic Rick, but have you ever seen a Rivs OE impeller versus say a Duralast impeller? It doesn't make you feel confident about using it, that's for sure.

manofmany wrote:

A little off-topic Rick, but have you ever seen a Rivs OE impeller versus say a Duralast impeller? It doesn't make you feel confident about using it, that's for sure.

NO, I've not had the chance to compare. Which one was the better of the 2, I can't tell from your sentence.?

OE by a mile. I've still got one laying around. I'll have to take a picture. The Duralast uses thin metal propellers.

...do you think:

- radiator or cooling system blockage from fragments from old water pump accompanied by crud, or accumulated crud from sitting that's now (partly) blocking something...
- small head gasket leak only shows up when engine is working against a relatively large load. Idling would not be such a load. Moving would be...
- more likely (unfortunately) a crack in the head or the block caused by overheating when the first WP failed, somehow from the exhaust passages into the water jacket...
- some engine accessory (the air conditioner?!?) that is failing and presenting way too high a load (unlikely)...
- thermostat "works" but incorrectly (I am grabbing at straws on this one)

Thinking about it I am guessing a wack new WP or a block crack/leak. Just sayin'.

Albertj

Thanks for the insight guys. Gives me more to work with. I'll plug away at it and see what I can find.

Another symptom I forgot to mention was that it has nice hot heat, then just before the temp pegs, it goes ice cold. Very strange....

toomanytoyz wrote:

Thanks for the insight guys. Gives me more to work with. I'll plug away at it and see what I can find.

Another symptom I forgot to mention was that it has nice hot heat, then just before the temp pegs, it goes ice cold. Very strange....

Heat goes ice-cold from the exhaust purging hot coolant from the cooling passages back out the overflow, I suspect. The water pump goes into cavitation (impeller spins in big air pocket) and there's no new hot coolant in the heater core, so heater core cools off, and at winter temps it gets cold quick.

Albertj

Behaves the same way with no thermostat in it. Overflow tank fills, but the gauge stays at 1/4 now. Very little heat from the vents. Top of the radiator still cold near the cap, but the upper hose is now hot. Still seems to have air in system at bleeder. Coolant looks cloudy, but not foamy. Oil is clean. No smoke from the tailpipe.

*shrug*

Sounds like head gaskets?

I think this car just became a trade-in.

toomanytoyz wrote:

Behaves the same way with no thermostat in it. Overflow tank fills, but the gauge stays at 1/4 now. Very little heat from the vents. Top of the radiator still cold near the cap, but the upper hose is now hot. Still seems to have air in system at bleeder. Coolant looks cloudy, but not foamy. Oil is clean. No smoke from the tailpipe.

*shrug*

Sounds like head gaskets?

I think this car just became a trade-in.

You may not have the appetite for this -- but have you considered shopping the regional yards for a replacement engine? There are a *lot* of L67s out there. What you'd want to do is find a donor Bonneville or Olds 88 or 98. The Olds' are not driven hard. Some Bonnies are not driven hard you have to look at the car to tell though.

And as you know some yards install.

Point is it's possible you could get a replacement engine without a mortgage (or even a loan in some parts). Do you think you Might want to have a look?

I actually have a spare GTP as a parts car, so I do have the engine. And I do have the mechanical ability and place to work on it... But I never really got the love for this car, and this may have let the rest of the wind out of the sails. Bummer. I really wanted to like it.

toomanytoyz wrote:

I actually have a spare GTP as a parts car, so I do have the engine. And I do have the mechanical ability and place to work on it... But I never really got the love for this car, and this may have let the rest of the wind out of the sails. Bummer. I really wanted to like it.

I get it.

Albertj

toomanytoyz wrote:

Behaves the same way with no thermostat in it.
Overflow tank fills, but
the gauge stays at 1/4 now.
Very little heat from the vents.
Top of the radiator still cold near the cap, but
the upper hose is now hot...

Sounds like head gaskets?

No, I really think it sounds like a water pump that isn't pumping...

I realize that it sounds insane in a world where we could previously expect very simple parts to work properly, but after my experience with back-to-back sour Delco pumps for both water and power-steering fluid, I don't think it's unlikely any more. My reasoning is this:

Thermostat made no difference - water pump more likely.
Overflow tank fills - water is boiling from not moving, water pump likely.
Gauge doesn't register the obviously very hot coolant temp - water pump isn't circulating.
Heater doesn't work - coolant not being pumped through the heater core.
Return side of radiator is cold - no coolant flow.
Upper hose gets hot - the upper coolant is getting hot by convection...

Eldo wrote:

toomanytoyz wrote:

Behaves the same way with no thermostat in it.
Overflow tank fills, but
the gauge stays at 1/4 now.
Very little heat from the vents.
Top of the radiator still cold near the cap, but
the upper hose is now hot...

Sounds like head gaskets?

No, I really think it sounds like a water pump that isn't pumping...

I realize that it sounds insane in a world where we could previously expect very simple parts to work properly, but after my experience with back-to-back sour Delco pumps for both water and power-steering fluid, I don't think it's unlikely any more. My reasoning is this:

Thermostat made no difference - water pump more likely.
Overflow tank fills - water is boiling from not moving, water pump likely.
Gauge doesn't register the obviously very hot coolant temp - water pump isn't circulating.
Heater doesn't work - coolant not being pumped through the heater core.
Return side of radiator is cold - no coolant flow.
Upper hose gets hot - the upper coolant is getting hot by convection...

With the cooling system buttoned up, and the spark plugs out, thing to do is pressure test for a coolant leak. and/or pull the plugs to check for AF residue although the car may not have been driven enough to generate any.

If no leak on plugs-out pressure test - - WP

if leak - cracked head, cracked block or wack gasket.

Albertj