89 ST... I was almost home last night and the temperature needle started rapidly climbing from its normal 12 o clock position. I pulled over and turned off the car and turned on the heat but only cold air came out. The expansion tank was bubbling something fierce. I waited for it to cool and resumed driving. The needle started to climb past normal again, but the suddenly stopped and hot air started coming out of the vents. It took forever to stop by bubbling in the tank. I checked the coolant and it was not low. I actually replaced the thermostat about a month ago because if randomly overheated like this. I have not had any problems again until now. I put a new water pump on about a year ago while changing the timing belt. I ran it again today for about 15 minutes, it didn't overheat and the lower radiator hose became hot after it got up to temperature so it appears that the coolant is flowing. I did notice that when the engine is cool, if I squeeze the upper radiator hose I can hear a hissing sound somewhere close to the firewall at the top of the engine. However other than the water that boiled over it isn't losing coolant that I can see. I even ran UV dye in it today and could detect no leaks. Any ideas? Thanks for the help.
If you put a new rad and thermo in it a month ago it might still have air pockets in the cooling system. Sometimes it has to be bled several times to get them out. Also, did you replace the radiator cap as well?
I didnt put in a new radiator, just a new thermostat. I did replace the cap not too long ago. Should I have done something special to get the air out?
Best scenario: You can try to "burp" it to get any trapped air out of the system. Squeeze the hoses until clear of any air bubbled at the top. It's a closed system and when fully sealed it should run at slightly under 12 o'clock. Worst scenario: Sounds like head gasket time...hot combustion air is getting into the water passages and causing the bubbling, especially if you hear any gurgling sounds coming from under the dash or heater core. Also the temp gauge may jump up real fast, so be careful that it doesn't overheat to the point of real damage below. I say this from past experience on my 87 GTS. Vic
Oh noes hopefully it isn't the HG. That repair cost is more than the car is worth. Have you ever tried the head gasket repair stuff? The Bars Leaks stuff fixed the intake manifold gasket leak on my GMC Yukon. I've never had a HG go bad before.
I don't think its a good idea to put that stuff in your engine...it will probably clog up the radiator and heater core, etc., not to mention that it really wont even come close to solving the issue. I would be afraid to drive it too far with that goop in it, fearing that it will relapse. I did my own HG on a 3sge with 195, 000 on the clock. Now I'm at 240 thou and it runs like new (almost). I think your FE is about the same amount of work, but its not a job for the faint of heart if your not mechanically inclined.
Jack the front of the car up as high as you can, you want to make the radiator cap the highest point in the cooling system. Have a bottle of coolant or distilled water handy. Fill the overflow bottle to the full line and put the lid back on. Turn the heater on full. Now take the radiator cap off and start the engine. Let it run until it warms up and the thermostat opens, you should see the fluid level in the radiator drop when that happens. Top the radiator up. You should see bubbles rising to the top of the radiator neck and bursting, when you get one, top the radiator back up. Alternately squeeze the top and bottom radiator hoses, you should see more bubbles rising to the top. Keep topping the radiator up until you're not getting bubbles any more, then put the radiator cap back on. Congratulations, you just bled your cooling system If its still overheating after bleeding then put a new radiator in it, even if it looks like its flowing well and the coolant is clean it could still be clogged somewhere inside. If its still overheating after that, its time to pull the head off.
Good luck...keep an eye on the needle. If it starts swinging erratically to the hot pull over or get it home and consider your options. I personally think most drivable 4th gens are worth more than the expense of a HG job. Vic
