Hello everyone, I have a 1999 saturn sl2 DOHC that is overheating. It started with the overflow coolant cap being busted so I replaced the entire housing just cuz it was nasty looking and cheap. Then the problem occured again a month later idling at a gas station. So I ordered a new thermostat and coolant temperature sensor and just replaced both. The car didn't even have a thermostat in it the entire time I've been driving it(recently purchased). Car has a new radiator on it, now a new thermostat, new coolant container, new coolant temperature sensor, AND the fan is turning on properly when it starts to overheat. I really hope it's not a blown head gasket. Can anyone shed some light on this situation because im now stumped and my car is overheating immediately with a thermostat rather then it didnt with no thermostat.

 

have you had the system pressure tested?
when you start the car from a cold start
--how long does it take to overheat and exactly where is the coolant escaping from?
--any white smoke out the tailpipe?
--does the upper radiator hose get hot? If so, how long does it take?


SES light on? Ant stored codes?

 

I haven't had the system pressure tested yet, I literally just got done putting everything back together. It took about 10 minutes from cold start to overheat. The temp light was on in the car and the temperature was maxed out on the guage but no coolant was spilling out. It has a newer water pump on it also. I didn't check the upper radiator hose, I just shut it off and called it a night.

 

No white smoke was coming out of tailpipe so good on the head gasket

 

check that hose. if it is not getting hot, it sounds like the system is not circulating coolant, either due to a bad water pump or possibly some type of obstruction. The missing thermostat you inherited makes me lean towards the latter, as this would allow the car to run with a minimally restricted flow at all times, not just when it gets up to temp.

You stated that the cooling fan does come on at the appropriate time but is not enough to stop the runaway temperature rise. It is possible your cooling fan is no longer spinning at full RPMs.

Suppose the new thermostat could also have failed closed

However, for the cooling fan to have little to no effect on the situation makes me think that the coolant is not circulating. Remember where the coolant temp sensor is relative to the radiator... the ects only measures what is going past it --- if what is there is not moving, then it just reads the increasing temp of the same plug of fluid.

Temp rate increases like that should not be occurring in a sealed, properly pressurized and circulating cooling system

 

You really need to pressure test the system. And don't forget the radiator cap. Somtimes they get weak and can really mess with you.

 

For re-emphasis

 

Problem found today. The housing for the thermostat is missing an eyelit guide that the stem of the thermostat is supposed to sit in so it doesn't close all the way. Just need a new housing. Thanks for the help everyone and I'll make sure to pressure test it after I get the new housing!

 

so rather than replace the housing and fix it properly, the previous owner just took out the thermostat and tossed it over his shoulder. Nice. Well, that explains alot. But, as you said, still a good idea to get it pressure tested. If the previous owner addresses problems like this, there may be chewing gum somewhere in the system used to plug a hole......

 

My buddy is a dealer and bought it at an auction. Low miles, one owner, older lady drove it. New ac system, new radiator and water pump. But you could tell it overheated at one point and coolant overflowed from the container was everywhere because they didnt clean it up well in the engine bay. Whatever mechanic fixed this last did a half a$$ed job and screwed the lady over. Atleast everything is taken care of now.