Question-------------------------
Followup To
Question -
Hello!
I have a 97 Pontiac Trans Sport Montana that always wants to overheat. I've recently replaced the lower intake gasket and water pump, and didn't have any overheating problems after doing either, so I've all but ruled those 2 items out.
Here is what is happening: when starting it up cold, it begins to warm up after 10 minutes or so of idling. The gauge rises to the normal point where it would sit (around 190-200 according to the gauge), but instead just keeps rising. At this point, the upper radiator hose (from the thermostat housing)feels pressurized, but is not hot. The lower hose (from the water pump) is pressurized and hot, however. Sometimes if I bring the RPMs up to around 2k and hold it for 10 or 20 seconds, the temp needle will temporarily go back down to near normal, but it inevitably climbs back up, and overheats if left running.
All the while, I've got no heat coming from the vents.
I've opened up the bleeder screws above the water pump and on the thermostat housing to let any air in the system out, and both squirt out coolant when I open them up (with the engine running), so I think I can eliminate that too. Incedentally, when I did this, I got HOT coolant from the bleeder by the water pump, and room temperature (well, outside temperature) coolant from the one on the outlet side of the thermostat housing.
I think the only thing left is the thermostat? What do you think? Thanks a lot!
Bryan
Answer -
WHY did you perform the initial work ?.
Could be faulty thermostat.
Could be faulty electric or mechanical FAN CLUTCH not operating correctly.
Could be a leak in the head gasket(s) whereas cylinder(s)combustion pressure is getting into the cooling chambers of the engine.
autohelp
Hi again,
I replaced the lower intake gasket because coolant was leaking into my oil - a common problem on these 3.4 liter V6s from what I've read. I put the water pump in because it started leaking around the pulley and spraying coolant onto the serpentine belt. I did the lower intake gasket about 4k miles ago, and the water pump about 700 miles ago. No problem with overheating after both of those.
The electric fan is coming on at about 220 degrees, so the switch seems okay. What would be the best way to tell if it's a head gasket(s)?
Thanks again,
Bryan
AnswerI have seen many occassions when anti-freeze gets into the engine oil this mixture tends to accumulate a sludge type of gummy deposit into the lower and middle cooling tubes of the radiator core and thus restricts coolant flow to ONLY the UPPER portion of the radiator. In such cases the ONLY resolution is to replace the radiator with a NEW one. Do NOT have yours rebuilt, cleaned, flushed or other. Install a NEW one.
NOTE: Just because you can visually see coolant flowing thru the UPPER radiator tubes when viewing into the radiator cap opening, You CANNOT see if the middle and lower tubes are expelling coolant flow.
I would replace the thermostat FIRST and see if your problem is resolved.
To check for possible combustion pressure getting into the coolant chambers of the engine:
1. Remove all the spark plugs from the engine.
2. Remove the radiator cap and make sure the coolant level is FULL to the TOP of the radiator.
3. Using the hose from a COMPRESSION TESTER, Remove the check valve from the bottom of this hose.
4. Thread this hose into the engine cylinders.
5. Apply about 80 lbs of constant air pressure onto the hose in step # 4.
6. Watch the coolant level in the radiator for ANY bubbles.
7. Do this on all of the engine cylinders.
8. If you see any bubbles coming from the radiator, This is a sign of a hea gasket problem and or a possible faulty intake gasket.
Let me know what you find.
autohelp
