Question about 1998 Cadillac DeVille
THEN U MOST LIKELY HAVE A LEAKING HEAD GASKET, VERY COMMON PROBLEM ON THIS V8 NORTHSTAR ENGINE.
Posted on Nov 12, 2009
When the car is completely cool,check the electric fan(s) for smooth rotation.
Clean/check/change the thermo sensor,contact and wire.
Excavate air pocket in coolant system / check for head gasket leak
This test will kill two birds with one stone.
MAKE SURE THE COOLANT SYSTEM and ENGINE IS COLD!
RAN THIS TEST IN A WELL VENTILATED AREA ONLY!
You will spill some coolant during this air pocket purge test.......BE KIND TO THE ENVIRONMENT and ANIMAL please clean up after the test!
Put the front end on a pair of ramp or park your car on a VERY STEEP HILL (radiator facing top of the hill) .
Top of the coolant reserve tank
Let it ran for 10-15 minutes.
Monitor for air pockets escaping from coolant reserve tank.
Small amount of bubbles is OK at 1-5 minute mark
After the thermostat open up (after 195 F warm up) at
5-12 minute mark or after high idle you should see less bubbles.
If you do not see any in rush of bubbles then your thermostat may be partially stuck or rusted badly inside the thermostat hosing.
Give the thermostat host few gentle taps.
If you see larger bubbles surfacing after 15 minutes then should do a hydrocarbon (HC) dye test to test for potential head gasket leak.
Let engine cold down and top off coolant reserve tank.
Start monitor for coolant lost
A coolant flush is require every 2 years or 24,000 miles.
I recommend the thermostat that has a relief pop-let to reduce the change of burst radiator and coolant hoses.
Make sure you get a new thermostat gasket,black RTV and fresh coolant for the job.
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Posted on Dec 05, 2009
He said it is running hot, not overheating. What is the temp its running at? Most caddy mechs know the Northstar runs very hot and unless the ac is on the fans won't even kick in to around 225 low to 235 high.
Posted on Nov 14, 2009
Have you check the thermostat switch, which the unit sense the temp and turn on the cooling fan; also make sure the fans is not faulty. no not run 100% water in the radiator. 50/50 will be good in cold weather, hot go 75/25 antifreeze and water.
Posted on Nov 12, 2009
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Posted on Jan 02, 2017
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