I would go ahead and replace the thermostat and the radiator hose. if that doesn't fix the problem, you may have a cylinder head problem.Unless the fan does notcome on when the car gets hotor the water pump isleaking.

thanks for the info on flushing heater core. therm is new and hoses are fine.

My 99 sable is having this same problem. My temp started jumping around, the dial would move up toward H then it would move down toward C, just back and forth while going uphill. I noticed steam and coolant spraying from the plastic recovery tank, and assumed My coolant level was low and that was what caused the temp guage to act wierd. The recovery tank had a small leak so I replaced it along with a new 180 deg thermastat and flushed out the system extremly well. I drove the car around for about 30 minutes everything was fine so I thought it was fixed. Except!! later that evening I test drove it once again, I had driven about 5 miles and heard a thump, I stopped and looked under the hood. The resevoir cap was loose and it had sprayed coolant everywhere. I thought I had left the cap loose. I put some more coolant in it and went back home and let it idle for about 30 minutes everything was fine , the temp didn''t go up or down, the heater worked, no coolant was leaking anywhere. So I went for another test drive, the resevoir cap blew off again, but the temp stayed normal. I stopped, andcut the car off. The fluid was at the top of the reservoir and almost over flowing. I restarted the car and it sucked the fluid back inside the motor. I returned home and let it idle for almost an hour and nothing happened, everything worked fine, heater worked great, and the temp stayed constant.


Sorry for the long post, but this car is driving me nuts. I''m a sub mail carrier and car problems are very stressfull!!!!! ANY IDEAS!!!!!!!

@minnnow

from the sounds of it, the threads on the recovery tank may be shot or the cap is shot. if this is a system like my wife''s where the recovery tank is pressurized (no radiator cap, pressure cap on recovery tank) then you may have gotten a bum tank or cap. the thermostat may also be sticking and causing the coolant to build up on that side of the system and blow the cap.

The system must be pressurized, the recovery tank cap is a 16 lbs psi cap. I hope I''m lucky enough to have bought a bum tank.


I would like to wish everyone here a Merry Christmas!!

yeah... sounds like the threads are crap on the tank or cap.

The guy at the shop says iI have a blown head gasket. He says the reason the cap blows when its driven down the road is that the exhaust gases are going through the blown gasket and putting the extra pressure on system. What is involved in replacing a head gasket? I know the heads probably need to checked for cracks, but will they have to be reworked (what is reworking?) and would this be a good time to replace freeze out plugs? I know I sound like wimp, I can change/replace starters,alt, water pumps/ brakes and stuff like that but I''ve never tried to take an engine apart and put it back together.

ah... that would do it. reworking is making sure the head is not warped and resurfacing the gasket surfaces (cleaning and machining if necessary). This gets the head into a better working condition. You will need a torque wrench that is metered for the range the bolts on your engine need. you may also need numerous sockets/drivers to get at those bolts. If the freeze plugs are not warped (bulging) I wouldn''t worry about them. to replace the head gasket, you also have to replace the intake gasket (if it doesn''t come off cleanly) as well as the valve cover gasket on the head involved AND you will be required to take numerous other things off if they are in the way (wire harnesses, spark plugs, wires, vacuum lines, etc). It is a very involved process. and if you don''t keep absolute track of every nut and bolt, it may not work when it''s put back together (or at least not for very long).

Thats why I''m letting the shopo fix it. Thanks for the replys, there is a lot of helpful info here. Thanks guys!!!!!!

You''re very welcome. We do try our best to help if we know anything about the issues.