Not a stuck open thermostat.

[rockfangd]

I kind of doubt it is air in the system, but I have a purging funnel for cooling systems. It makes even the most difficult cooling system easy to purge, and without making a mess. I always recommend having front end elevated funnel or no funnel, so that the filling point is always the highest point

[adallak]

Well, the saga is going to continue... Now, my engine is overheating. Yesterday the temps were around 185-187 at 40 - 50 MPH. Today they climbed to 195 under the same driving conditions. The thermostat opens up around 185. My car used to be running at 181⁰F for years. 

I might be losing a bit of coolant. Just could not be sure because some is always lost when you replace a thermostat. I added distilled water. The could be 0.75 liter of distilled water instead of 50/50 mix. But I do not think that could cause any problem.

A blown head gasket? That is not typical for LT1 (well maintained) engine, but who knows...

Any quick and unquestionable signed of a blown head gasket? Any fast ways to check it out. I am at a loss... I do not know if the strange behavior of coolant temperatures that started a few months ago had something to do with a blown head gasket. This could be the end of my Fleetwood... Too bad. 

 

[BodybyFisher]

You have no misfire or vapor out of the exhaust, so my initial feeling is no blown headgasket.  You can use the block tester to test for hydrocarbons in the cooling system, I recently saw the block tester kit at Harbor Freight at a good price compared to the $50 balkamp make.  

You have checked to make sure all air is out and you aren't getting cavitation?

Intermittent fans, might be difficult to diagnose if a fan motor is stopping when it should run.  

Check the lower hose for collapsing

How old is the radiator?

I don't think 195 is anything to panic over, even though you saw lower temps yesterday.  AC is operative? 

Check for "tar paper" material blowing over the radiator partially restricting the air flow through the radiator. 

Are you getting any transmission codes?  A slipping torque convertor clutch might generate more heat. 

Just brain storming here.

[Bruce Nunnally]

Yes, a change in operating temps is suspect.  That said, 10 degrees above thermostat temp for cruise is expected.  If thermostat at 185F it should always have operated at least at that level?

Are the fans both coming on?  Does it get hotter than normal at idle as well?  Is the radiator clear?  Could it be time to flush or replace the radiator?

[adallak]

8 hours ago, Bruce Nunnally said:

Yes, a change in operating temps is suspect.  That said, 10 degrees above thermostat temp for cruise is expected.  If thermostat at 185F it should always have operated at least at that level?

Are the fans both coming on?  Does it get hotter than normal at idle as well?  Is the radiator clear?  Could it be time to flush or replace the radiator?

Bruce, Mike,

Thank you for the replies.

No bubbles in the recovery tank as far as I can see. The construction of the tank does not really let you see if there are some, though. No oil or coolant contamination. No white vapor out of exhaust pipes. The engine is super smooth. No codes. 

A few months ago the car started running at 167 -170⁰F. It used to be STEADY 181⁰F for thirteen years. Masking the radiator with cardboard first raised the temps to 179, but later would not make any difference. NOW THAT makes me think there could have been blockage of the passages inside the radiator. Anyway, I gave up on monitoring the temps until yesterday when it got really hot, I could feel it and immediately ran onboard diagnostics to see it climbing to almost 200, which NEVER happened before. The both radiator hoses were hot and pressurized. I probably did not get to the point when electrical fans kick in, but if there were problem with radiator, they would not help much either. 

Something tells me it is not a head gasket. Unfortunately I cannot flash the radiator with garden hose or remove knock sensors saving as engine block plugs to let old gunk out of the system.

Will infrared thermometer tell something about the condition of the radiator or it is a waste of money? 

8 hours ago, Bruce Nunnally said:

Yes, a change in operating temps is suspect.  That said, 10 degrees above thermostat temp for cruise is expected.  If thermostat at 185F it should always have operated at least at that level?

Are the fans both coming on?  Does it get hotter than normal at idle as well?  Is the radiator clear?  Could it be time to flush or replace the radiator?

Well, the saga is going to continue... Now, my engine is overheating. Yesterday the temps were around 185-187 at 40 - 50 MPH. Today they climbed to 195 under the same driving conditions. The thermostat opens up around 185. My car used to be running at 181⁰F for years. 

I might be losing a bit of coolant. Just could not be sure because some is always lost when you replace a thermostat. I added distilled water. The could be 0.75 liter of distilled water instead of 50/50 mix. But I do not think that could cause any problem.

A blown head gasket? That is not typical for LT1 (well maintained) engine, but who knows...

Any quick and unquestionable signed of a blown head gasket? Any fast ways to check it out. I am at a loss... I do not know if the strange behavior of coolant temperatures that started a few months ago had something to do with a blown head gasket. This could be the end of my Fleetwood... Too bad. 

 

[rockfangd]

What do you consider overheating?

I realize you ran at a temp for years, but things change with parts, wear, miles, etc... 

The question about the torque convertor is a really good one. Are your RPMs the same as always? A slipping torque convertor surely causes more heat.

If you are not climbing above 220*f I would not stress very much. 

I would not change the (Chemistry) of the coolant though. Too much or not enough coolant mix will result in undesired results. 

I would surely not retire a Fleetwood for this. 

[adallak]

Have not noticed anything unusual transmission-wise. No codes. 

I am thinking about probably replacing the radiator. Not sure flushing will do any good. Some gunk builds up despite I replace the coolant every two-three years. Never used Dexcool. Used Bars leaks for a year or so, then got rid of it. 

[rockfangd]

Not a bad idea to replace the radiator if in doubt. Coolant schedule is good. Did they run Dexcool in 95? I thought 96 started that.

Tabs have to be put in correctly otherwise they may plug certain passages. Not sure where yours would go. If this is a 5.7l I have never used tabs in one of them. I did do alot of intake gaskets on them. 

[adallak]

Ordered a new radiator. 

[BodybyFisher]

36 minutes ago, adallak said:

Ordered a new radiator. 

I think that is a smart thing to do.  It is very possible that years of cooling system tablets has built up and is clogging up the radiator.  

Looking forward to your results.

Don't forget to add more tablets 😉😀 I also didn't think the 5.7 needed the tablets, I know the 4.9 and NS needed them.

[adallak]

😂😂😂. Tablets were BIG on this board! No, for the last 12 years there were no tablets in the system. It is the rust, I believe. We will see. 

[BodybyFisher]

56 minutes ago, adallak said:

😂😂😂. Tablets were BIG on this board! No, for the last 12 years there were no tablets in the system. It is the rust, I believe. We will see. 

Keeping my fingers crossed you get back to a cool 181° 👌 good luck with that radiator swap

[adallak]

Got the new radiator, but before I remove the old one I am still trying to figure out. Took it for a test drive. Just in 4 miles I had to stop. The temp climbed to 216F if I trust the temp sensor (I do) , opened the hood and saw this... Steam and coolant gushing out of the bottom of the expansion tank cap. Barely made to a friend's home. 
I knew it was coming and did not drive car till today. It seems like the radiator does not get any flow at all. The lower part of the inlet hose as well as whole radiator is cold.l

The both fans kicked in around 197 as they always did, but they were useless without radiator. The temp sensor is fine, even if it were not it has nothing to do with the stat opening and coolant circulating through the radiator. Any chance the water pump failed? It has been replaced by me 3 years and 11,000 miles ago. It is Gates. I am extremely frustrated since I am far away from home. Have plenty of tools in the trunk, though.

 

 

 

[BodybyFisher]

I would buy the Harbor freight block tester and test the coolant, to eliminate that from the potential list of problems.  

While at idle check that the upper hose is holding pressure.

If the upper hose were cold it would indicate that no coolant flowed through it.  

11,000 miles on the pump should eliminate that unless the impeller backed off but that would be a fluke.  

I can't help but think the radiator is plugged and gunked up.  

[Logan]

I would take a close look at the water pump impeller. Some pumps are actually using plastic ones. The pump could also be a counterfeit Gates.  

https://www.impalassforum.com/threads/water-pump-impeller.341985/

[adallak]

50 minutes ago, Logan said:

I would take a close look at the water pump impeller. Some pumps are actually using plastic ones. The pump could also be a counterfeit Gates.  

Thank you, Logan. Unfortunately, that's what my guts tell me.

Do you think a failing pump still can force coolant through the (partially clogged) heater core, but cannot force any coolant through the radiator? The latter was absolutely cold when the hot coolant boiled over.

If I find no severe restriction in the radiator and nothing wrong with the thermostat, the next suspect would be the pump. Since I will have to take it off to check the impeller, it makes sense to have a new one waiting. I would just put the new one. Not a favorite job, especially in this hot and humid  weather. Oh well.

I may ask for too much, but any way to check the operation of the pump without taking it off? It is such a pain on LT1. 

 

[Logan]

I don't think the pump is doing anything.....saw one of LT1 post where the impeller was just spinning on the shaft. 

[adallak]

8 minutes ago, Logan said:

I don't think the pump is doing anything.....saw one of LT1 post where the impeller was just spinning on the shaft. 

Thanks. I am ordering a pump and will wait with touching the cooling system until I have it delivered. As far as I recall the impeller was plastic. The pump was well made, though. 

[rockfangd]

My thoughts exactly on the impeller. I have a hard time trusting any parts anymore. OEM or aftermarket. I have a feeling the impeller was starting to slip on the shaft and now just spins on it. I have seen them split, fall off, you name it.

Still not a bad idea to replace radiator if original. Expansion and contraction, contaminants, shifting, all take a toll on it. 

If temps at the engine are hot at the engine but not at the radiator that points to no flow. Either thermostat or pump. In your case likely pump

[adallak]

The common failure of GM radiators of 90sn has been a crack in the plastic radiator side tank. I have replaced it 11 years ago (just the side tank) and hoped I would never have another issue with the cooling system.  Well the pump stated to leak 3 years an 11,000 miles ago and according to the records it was replaced some 50,000 miles ago by the original owner or his dealership.

The pump will arrive on July 7. Before that, it does not make sense to touch the cooling system. Will update, of course. 

[adallak]

17 hours ago, BodybyFisher said:

I would buy the Harbor freight block tester and test the coolant, to eliminate that from the potential list of problems.  

While at idle check that the upper hose is holding pressure.

If the upper hose were cold it would indicate that no coolant flowed through it.  

11,000 miles on the pump should eliminate that unless the impeller backed off but that would be a fluke.  

I can't help but think the radiator is plugged and gunked up.  

Thanks, Mike. I am waiting for a water pump. Till then will not touch the cooling system. I want to have everything ready if it appears the pump is indeed bad. The radiator is here as well. 

 

[BodybyFisher]

PLASTIC?  I'm looking forward to the solution on this one, Armen 🍿🍿🍿

[BodybyFisher]

2 hours ago, adallak said:

The common failure of GM radiators of 90sn has been a crack in the plastic radiator side tank. I have replaced it 11 years ago (just the side tank) and hoped I would never have another issue with the cooling system.  Well the pump stated to leak 3 years an 11,000 miles ago and according to the records it was replaced some 50,000 miles ago by the original owner or his dealership.

The pump will arrive on July 7. Before that, it does not make sense to touch the cooling system. Will update, of course. 

July 7th, my birthday!  70!  I am hoping for a 70th edition C8, we will see 🙏😄

The learning never stops.  If this 11,000 mile waterpump is toast already things are worse than I thought.   Do you recall where it was made?  You can't even assume an 11K part is good anymore, amazing.  

Can't wait to see the result here 

You gotta stop winding that Fleetwood out to 9,000 RPM Adallak lol

 

[adallak]

9 minutes ago, BodybyFisher said:

July 7th, my birthday!  70!  I am hoping for a 70th edition C8, we will see 🙏😄

The learning never stops.  If this 11,000 mile waterpump is toast already things are worse than I thought.   Do you recall where it was made?  You can't even assume an 11K part is good anymore, amazing.  

Can't wait to see the result here 

You gotta stop winding that Fleetwood out to 9,000 RPM Adallak lol

70. The age of wisdom and a fresh start! ))

9,000. Lol Not sure I ever made 3,000. 

Most likely it was made in China. Where else? Nevertheless, the quality of auto parts went down regardless of the origin, IMHO. It can be a pain to replace a part, but doing it again and again is so annoying. 

 

[BodybyFisher]

2 hours ago, adallak said:

 

You are so right.