Strange engine overheating.

[London]

I'm doing a little diagnosing of my engine right now and thought I'd come here for some outside opinions. Last night I was driving from my house when I realized my engine was overheating. I turned around, put the heater on full blast, and got nothing but cold air (it was around 70 degrees last night). Made it home, and as soon as I pressed the brakes a bunch of water spilled all over my foot from the AC/heating vent under the steering wheel (you know, the one a little above and forward of the gas pedal). The day before I noticed a water leak on the passenger side; I suppose it was also from the air vent.

Turns out the coolant was too low. Filled it back up and took it for a test drive only to find the temperature varying quickly and wildly, and alway just about to overheat at its hottest. The defroster works again now. From what I've read on the matter, I am thinking an air bubble was trapped in the heater core and mostly found its way out. I just finished trying to get whatever may be left of this (noexistant?) air bubble out but didn't see anything. I also didn't have my defroster turned on, so I guess I'm going to have to do it again just to be sure. I'm also thinking the thermostat may be a suspect. The car is a 93 Thunderbird w/V6.

Anyone have any thoughts on the matter? Thanks!

 

[heavyzee]

yea i would say thermostat... its a cheap and easy fix.... and the 1st place a mechanic would start anyways... autozone/pepboys/advanced should be $12-15 for the thermostata, and make sure you replace the gasket when you remove the old one

 

[bwdilli]

Leaking heater core would also cause the symptoms you described.

 

[London]

Errggh... I should have typed, "Heater core" rather than "Heat exchanger." It's a hectic day!

 

[London]

Okay- still doing homework on this but I'm about 60% sure it's the thermostat. When test driving it this afternoon the engine didn't warm up whatsoever until I hit the five mile mark, at which it near instantly went up to normal temp. Pisses me off that my car is effed, but at the same time it's actually really fun and cool learning all this car stuff in the meantime. I love mechanical stuff.

 

[Charlie]

Thermostats are cheap and usually easy to get to. Replace it and see what happens.

 

[London]

No pressure in radiator hose; bubbles should have been bled by now. Probably the therm. Sucks that I don't have enough time to get this finished. Damn you sun, give me couple more hours!

 

[Randman]

Having a similar issue with my jeep right now.. 99' XJ.. Replaced rad cap, going to replace t-stat tomorrow.. Good luck

 

[London]

I've been thinking of the cap, too. It's just too bad I can't drive my car into town and have the parts store do a vacuum test for me! Funny how you have to HAVE a car to fix one!

 

[winchster]

Very doubtful that the cap is the culprit. Based on your information the tstat is the most likely culprit.

 

[winchster]

Having a similar issue with my jeep right now.. 99' XJ.. Replaced rad cap, going to replace t-stat tomorrow.. Good luck

On the later 4.0 the most likely culprit is the electric fan.

 

[Texas1911]

If it's taking miles to warm up it's because the thermostat is stuck open. You should replace the thermostat ... it will improve your gas mileage immensely because of the cold engine fuel enrichment value.

Water / Coolant can only enter the cabin via a leaking or burst heater core. The core should be located behind the glovebox next to the blower fan. The best way to do it is to pull the dash to access it, but on some cars you can do it by just removing the glovebox. You can look at the firewall in the engine bay and see where the coolant hoses run into it; those hoses feed the heater matrix.

The heater not blowing warm air is either a bubble, blockage, or the duct isn't working. Sounds like you got that figured out though.

The bigger concern is with the overheating you are exposing yourself to headgasket trouble if the problem is prolonged. It can be tough to diagnose a headgasket failure if it is small, but it will exacerbate over time.

 

[TexasRedneck]

Ford went to aluminum heater cores, but often didn't tell folks that the older coolants weren't compatible with the cores - in fact, even Ford didn't realize it until they replaced a buncha 'em under warranty. Sounds to me like the heater core is toast. The lack of heat is because the water level in the radiator was so low that all you had in the core was air - the water was so low that it wasn't makin' it to the core.
Trust me on this....or be prepared to buy an engine....BTDT!

 

[Dawico]

I vote for heater core also. As TX1911 stated, that is about the only way coolant can get into the passenger compartment. Low fluid levels can cause the other symptoms you are describing.

 

[fuelfather]

If you are having coolant in the drivers compartment, you have a leak that is coming from the heater core box. It could be a line or the core itself but that is a given before anything else. As stated above when the fluid gets low it will not give an accurate reading on the temp. gauge until some fluid makes contact with it. If the fluid is low enough, the thermostat will not open until there is extreme risk of engine failure.

 

[jocat54]

I think Texas1911 has it right--sounds like your heater core is leaking and possibly a bad thermostat. Temp gauge and thermostat won't work correctly if fluid isn't touching them. Sounds like you were low on coolant to start with (leaking heater core?) and when you added coolant you got an air bubble which caused the other problems.

Some heater cores are fairly easy to replace and others can be a real bitch, just not sure on yours.

 

[Leper]

Coolant on your feet is a heater core leak. That is a pain to fix. If it was about to be summer, I would tell you to connect the heater core hoses together to bypass it. Going into winter, that would kill all of your heat. If the temp was pegged you have probably done more damage. Hate to give you the bad news. As others stated, low coolant will not give you heat and the temp will show lower than actual. The tstat and cap may have been damaged by the heat, but most likely did not cause the problem. That body style had quite a few with core issues. I had the one in my old Lincoln mark 7 done. Same thing as your tbird. Had a guy do it on the side for $300 way back. Not a job I wanted to do and I worked on cars for a living back then, if that tells you something.

 

[Willy]

Having a similar issue with my jeep right now.. 99' XJ.. Replaced rad cap, going to replace t-stat tomorrow.. Good luck

My 04 Wrangler with the same engine had the same problem with erratic tempurature. It was the thermostat. The water pump goes out about every 100k miles. You might want to replace both. Costs about $100 for both if you get new antifreeze and flush the system.

 

[M. Sage]

I'm doing a little diagnosing of my engine right now and thought I'd come here for some outside opinions. Last night I was driving from my house when I realized my engine was overheating. I turned around, put the heater on full blast, and got nothing but cold air (it was around 70 degrees last night). Made it home, and as soon as I pressed the brakes a bunch of water spilled all over my foot from the AC/heating vent under the steering wheel (you know, the one a little above and forward of the gas pedal). The day before I noticed a water leak on the passenger side; I suppose it was also from the air vent.

Turns out the coolant was too low. Filled it back up and took it for a test drive only to find the temperature varying quickly and wildly, and alway just about to overheat at its hottest. The defroster works again now. From what I've read on the matter, I am thinking an air bubble was trapped in the heater core and mostly found its way out. I just finished trying to get whatever may be left of this (noexistant?) air bubble out but didn't see anything. I also didn't have my defroster turned on, so I guess I'm going to have to do it again just to be sure. I'm also thinking the thermostat may be a suspect. The car is a 93 Thunderbird w/V6.

Anyone have any thoughts on the matter? Thanks!

Look for leaks. If you don't find any... The 3.8 was (very well) known for headgasket failure.

You don't have coolant smell inside the car, do you? The water on your feet could be a heater core leak, not sure how hard it is in a 93 T-bird, but older Fords tended to be fairly easy to replace (the one in my old Bronco took about a half hour). Does the windshield steam up with the defroster on? Does the heat coming from the vents smell sweet?

 

[London]

No coolant smell, but I was just using water for coolant anyway since it was summer. No fog when defrosting, either. I can assure you from reading the Haynes manual that replacing the heater core is a huge PITA; nearly everything in the dash has to come out. Oh, yeah- and if you do it wrong the airbag will deploy and possibly kill you (if equipped). Thank God I don't have one.

So here's a question for you wrench-bending quiz-kids: The gasket for my new thermostat has a sticky side like a piece of tape. Should I disregard this and use gasket sealant on both sides? Looking at the rather rough textures of where the therm housing meets the gasket, I am skeptical a thinly glued-on gasket will keep a seal. Advice?

And thanks for all the help so far. You guys are the awesome! All my bases are belong to you.