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With the recent warmer temps >70 I've been seeing the temp gauge rise at idle @5/8 on the gauge the fans kick into high speed but temps continue to climb.

I pulled the purge line/orifice and ran a drill through it maybe some small crud but it wasn't blocked.

Back in the fall I had a crack in the passenger side tank and replaced the radiator but recall the core not being as thick as the original - I'd have to get the micrometer out but maybe 1/8-3/16" smaller, so possibly the radiator cooling capacity is lower.

At the same time changed the t-stat(supposedly fail open) it was different style and could also be contributing to my issues.

Debating about having the tanks replaced on the old radiator and going back to original style t-sat and running another block test before I do any of this.

There is no overheating under driving conditions accelerating hill climbs nothing only at idle for a minute or more in temps >70 and it comes back to 1/2 on the gauge after driving for 1/4mi.

I haven't noticed any coolant consumption or leaks/smell during these idle slight - overheating incidents.

Any other ideas?

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I would think you are on the right track.

First off, have you verified flow from the purge hose?

I only run delco radiators in the caddys so have not had the size issue but can only imagine with the knock offs out there.

I would say you have a flow problem. higher speeds keep it cooler.

Check your waterpump tensioner. may be seized up and not holding enough tension at idle.


GM FAN FOREVER

Nice, clean, luxury= fine automobile

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The first thing I did was remove the purge fitting/orifice and ran a drill all the way through, even though I could blow through it with it removed

I replaced the water pump tensioner and belt last fall after the radiator/hoses/t-stat because I was having the same issue with good flow through the purge line....it was a bit warmer the around early October - we still have a few warm days in the fall down here.

Basically the colder weather this winter has probably masked the flow issue - today it's 50F on the ride home and no issues, yesterday was 74 and it went past 5/8 at idle after a couple minutes in park(fully warmed up from the drive home both times)

Talked to 2 local shops and neither replace end tanks - pretty much what I figured more in labor than a new one

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The first thing I did was remove the purge fitting/orifice and ran a drill all the way through, even though I could blow through it with it removed

I replaced the water pump tensioner and belt last fall after the radiator/hoses/t-stat because I was having the same issue with good flow through the purge line....it was a bit warmer the around early October - we still have a few warm days in the fall down here.

Basically the colder weather this winter has probably masked the flow issue - today it's 50F on the ride home and no issues, yesterday was 74 and it went past 5/8 at idle after a couple minutes in park(fully warmed up from the drive home both times)

Talked to 2 local shops and neither replace end tanks - pretty much what I figured more in labor than a new one

The shops in your area must really be high priced... The inlet tank is about $45.00 and the shop near me charges $90.00 to replace a tank (my price was $70.00 because the shop owner is a friend of mine). I couldn't buy a radiator for $90.00. I had the inlet tank replaced on the '96 Seville I used to own - I took the radiator out and brought it to the shop. I watched my buddy replace the tank and he was done in 15 minutes which included powerflushing the core once the old, cracked tank was removed. A re-core would be more than a new radiator due to the labor involved. My Fleetwood Brougham had a brass radiator with brass end tanks. It began to leak after 19 years and I brought it to my bud's shop and he told me the core was shot and to recore would be more than a new radiator so I opted for the new radiator. I was disappointed when the new radiator was aluminum with plastic tanks. In retrospect, I should have have had him re-core the original unit...


Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Well that's that - block test failed twice.

Even got a consistent bubble stream every ~3secs at idle. Works out to probably 1 cylinder ~750rpm/4strokes/60s/min.

Not sure if I'll trade it or attempt to drop the engine myself. The machining work doesn't scare me just the logistics of dropping the engine without a lift

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thats a bummer. must be in the early stages of headgasket failure. Please keep us posted


GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Well that's that - block test failed twice.

Even got a consistent bubble stream every ~3secs at idle. Works out to probably 1 cylinder ~750rpm/4strokes/60s/min.

Not sure if I'll trade it or attempt to drop the engine myself. The machining work doesn't scare me just the logistics of dropping the engine without a lift

You don't need a lift - I've done two of them by pulling the engine from the top side.


Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Do you by chance have a link in the how-to or any tips advice - pictures usually help me the most.

I have to do some measuring on where the sub frame bolts to the body.

I recall a thread where someone built an a-frame lift and raised the body in his shop. I'm thinking similar but just running some 4x6's to the trusses in my garage, raising the rear tires on some ramps dropping the engine/subframe on a roller dolly I have access to, and raising the body with a 4x6 spanned from side to side - it may need to be blocked up to clear the exhaust.

I have access to plenty of high tonnage rigging/slings etc.

When they drop an engine with a lift the lift picks the body from the rails underneath the door hinge area right? Is any temporary bracing required to prevent the nose from sagging?

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Do you by chance have a link in the how-to or any tips advice - pictures usually help me the most.

I have to do some measuring on where the sub frame bolts to the body.

I recall a thread where someone built an a-frame lift and raised the body in his shop. I'm thinking similar but just running some 4x6's to the trusses in my garage, raising the rear tires on some ramps dropping the engine/subframe on a roller dolly I have access to, and raising the body with a 4x6 spanned from side to side - it may need to be blocked up to clear the exhaust.

I have access to plenty of high tonnage rigging/slings etc.

When they drop an engine with a lift the lift picks the body from the rails underneath the door hinge area right? Is any temporary bracing required to prevent the nose from sagging?

Hi, I had a similar case on my 99 Seville STS. When starting in the morning it would have steam from the exhaust just for the first mile. No water from the exhaust at idle. I thought I need to have a full repair of the head gasket which is not really economic on an engine with over 125000 mls on it. I tried it with a bottle of bar's leaks radiator repair simply because it was in my shelf ( I'm not getting any promotion or something ) and it stopped immediately ! After 1000 mls done its fine. Just need to replace the thermostat now bec. its stuck, but thats the least worry.

Anybody got experience with bluedevil, bars head gasket repair, hyper seal or similar kind of stuff for head gasket repair?

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Do you by chance have a link in the how-to or any tips advice - pictures usually help me the most.

I have to do some measuring on where the sub frame bolts to the body.

I recall a thread where someone built an a-frame lift and raised the body in his shop. I'm thinking similar but just running some 4x6's to the trusses in my garage, raising the rear tires on some ramps dropping the engine/subframe on a roller dolly I have access to, and raising the body with a 4x6 spanned from side to side - it may need to be blocked up to clear the exhaust.

I have access to plenty of high tonnage rigging/slings etc.

When they drop an engine with a lift the lift picks the body from the rails underneath the door hinge area right? Is any temporary bracing required to prevent the nose from sagging?

Hi, I had a similar case on my 99 Seville STS. When starting in the morning it would have steam from the exhaust just for the first mile. No water from the exhaust at idle. I thought I need to have a full repair of the head gasket which is not really economic on an engine with over 125000 mls on it. I tried it with a bottle of bar's leaks radiator repair simply because it was in my shelf ( I'm not getting any promotion or something ) and it stopped immediately ! After 1000 mls done its fine. Just need to replace the thermostat now bec. its stuck, but thats the least worry.

Anybody got experience with bluedevil, bars head gasket repair, hyper seal or similar kind of stuff for head gasket repair?

Steam from the exhaust would be normal in cold weather. It would occur until the engine warms up. As far as the head gasket repair in a bottle - they're snake oil. None will work with any lasting results.


Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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I am starting to believe that a minor leaking head gasket slowly leads to a thermostat stuck open. When the faulty thermostat is replaced, the car reaches normal operating temperature again, but this increase in temp causes the heads to expand just enough to breach the seals and almost instantly lead to a much more severe gasket breach.

I am just throwing out that if a thermostat gets stuck open, check for exhaust gases first before replacing it.

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