1996 Chrysler LHS overheating

KERRYE

MEMBER
1996 CHRYSLER LHS
6 CYL
FWD
AUTOMATIC
132,000 MILES

Car overheats, boils over after 5 mins of driving.
1. New thermostat installed.
2. New waterpump installed.
3. New radiator installed.
4. Head gasket pressure test. Passed.
5. Heater core not clogged. Free flow.
6. Water will flow freely through engine.(With garden hose attached to any port)
7. All air purged from system.
8. Car will idle for half hour with AC full on. No problem. But get in and drive.3 mins to overheat/boilover.
9. Checked to see timing belt is actually turning the water pump. Yes. At idle speed.
Only thing I can think of at this point. Maybe the timing belt tensioner is not putting enough pressure on the belt to turn the pump efficiently at high rpms?
Also, when the engine is running.(Idle). You can pinch the top radiator hose and not feel any water pushing through. But the pump is new and it is turning and the engine stays relatively cool. At idle.
Eventually, when the car does overheat, the top radiator hose becomes "pregnant" indicating the steam pressure building up in the engine.
The car never looses any coolant. Other than the boil over from the overheat. I don't know what is left to check! Help!

2 Replies

DOCFIXIT

MECHANIC
18,828 POSTS

Hi kerrye
Was car doing the overheating before any of the repairs you made? When you bleed is the bleeder on thermostat housing open? Has coolant been checked for traces of CO2 and HC?
Let me know

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Monday, September 15th, 2008 AT 1:45 PM

KERRYE

MEMBER
2 POSTS

Yes, it overheated a couple weeks before. At that time I replaced the thermostat and all was well. For 3 or 4 days. Then, the symptoms I described started. First, it would go 20 miles or so to boil-over. Then 10. Then 3-4 miles.
Yes, I did open the bleeder valve at the top of the thermostat housing each time I've refilled the system until the coolant came out in a steady stream. Every 10 minutes, I open the bleeder valve again to make sure no other air was left. Most of the time, clear stream. Sometimes, no stream. Just air. Then of course at overheat temps. Nothing but super hot steam and water.I have not done the co2 test, but I wil try this afternoon.