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1998 STS BLK/BLK/BLK
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Discussion Starter #1
Anyone experience normal operating temperatures up till around 20 miles? I commute to work 25 miles one way and as soon as I get within a few miles of work my temp guage goes over the top and coolant boils out the recovery cap.

I recently tried fixing this problem by replacing the thermostat and I figured a new water pump and belt would also help, but it didn't seem to. I replaced the radiator due to a crack in the tank about a year and a half ago. I never notice any coolant leaks under the car, and it just seems to boil out after a long drive. It gets up to normal operating temp in normal time of about 2 miles and holds rock steady till about 20 miles. Cooling fans seem to be working, but they do not stay on when the cars ignition is off and the car is really hot from boiling over? Car runs great, still has plenty of power, idles fine, do not see any smoke from the tailpipes or no water on the dip stick. The purge line seems to flow steady if pulled from the recovery tank. I have never had a car do this before! Any suqqestions?
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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69,374 Posts
The 97,98,99 Northstar is infamous for failed head bolt threads in the cylinder block. One or more head bolts loses clamping pressure and this allows combustion gasses to blow out into the coolant, overpressurizing the system, blowing off coolant, and overheating the engine from loss of coolant.

The test referred to is a "cylinder block leak test" which uses a chemical fluid in a tube which is placed in the coolant reservoir neck. A vacuum is applied to the top of the tube/fluid and air/gas from the space over the coolant is bubbled up through fluid. A color change from blue to yellow indicates the presence of exhaust products in the coolant.

Stores like Advance, AutoZone, and others will "rent" the tester - you buy the fluid. Or, look online for automotive cylinder block test tools....... try www.sjdiscounttools.com, Lisle #75500 Combustion Leak Detector.

BEFORE you go paranoid, check your coolant hoses for feel - hot upper hose, warm lower hose, hot heater hoses - to rule out circulation problems first.

Make very sure the purge line is free and flowing a small stream at idle.

You would need a GM service manual to figure out the fan sequence for your car - they vary in fan control programming, but I would think the fans should run with key OFF in an overheat condition.
 

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time for the block test.........
Anyone experience normal operating temperatures up till around 20 miles? I commute to work 25 miles one way and as soon as I get within a few miles of work my temp guage goes over the top and coolant boils out the recovery cap.

I recently tried fixing this problem by replacing the thermostat and I figured a new water pump and belt would also help, but it didn't seem to. I replaced the radiator due to a crack in the tank about a year and a half ago. I never notice any coolant leaks under the car, and it just seems to boil out after a long drive. It gets up to normal operating temp in normal time of about 2 miles and holds rock steady till about 20 miles. Cooling fans seem to be working, but they do not stay on when the cars ignition is off and the car is really hot from boiling over? Car runs great, still has plenty of power, idles fine, do not see any smoke from the tailpipes or no water on the dip stick. The purge line seems to flow steady if pulled from the recovery tank. I have never had a car do this before! Any suqqestions?
Did you ever solve this isuee, I have same with 96 DeVille , driving me bozonkers!
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Read Post #3 from 10 years ago, then start looking through "overheating" threads in here, Deville, and Engines; Northstar. Read the stickies in each forum - timeless necessary info.

Welcome to CF !!!
 
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