Random overheating!!!??

[daytonaturbo87]

At random my 2.5 is overheating. N/A engine here. I replaced the t-stat with a new one from the dealer, and purged the cooling system and all was fine for about a week, now today on the way home from work it started overheating again. On the trip back from work(maybe 2 miles max, city driving) the temp got to the 3/4 mark and started inching above right as I pulled in the driveway and killed the ignition. I could hear the rad fan spinning. The rad is only a few years old. I don't know what else the problem could be!?

Coolant level doesn't seem to be dropping, but I'll check the rad and reservoir again after it cools down. Definitely no coolant in the oil, no white smoke out of the exhaust, so other than the engine not staying cool, I've experienced none of the other usual head gasket symptoms. Any suggestions?

[TurboRon25]

Head gasket just starting to go. You did drill a small air bleed in the t-stat, right?
My 2.5TI spirit has been acting REAL goofy too. I'm going to get one of those combustion gas in the coolant testers 2morro and see if that is my problem.
Mine almost over heats the first couple times the t-stat opens after a cold start. Much worse when it is cold out. t-stat is drilled. Maybe I just need a new t-stat. Funny thing is, it did this last winter/spring and was fine all summer, and again it is giving me problems since Feb.

Ron

[shadow88]

I bet it's starting to die as well.

How's the heater?

[boost geek]

I bet it's starting to die as well.

How's the heater?

That's my guess. Pull off the heater core hoses, and flush them out either with air or water, my guess the heater core is clogged.

[mo' parts]

check the waterpump belt, make sure it is tight and in good shape. you can always bypass the heater core to eliminate that.

[looneytuner]

Tighten all the clamps. After cooling down, some coolant should be sucked back into the engine. You can have a hose that doesn't leak coolant but sucks air in instead of coolant. Also check the hose to the reservoir.
Plus there are two circuits for the fan. One when the ac is on and the other for the coolant temp.

[daytonaturbo87]

No I didn't drill a hole in the t-stat, is there really a need for it?, but I did put the front end of the car up on the ramps(pretty high ramps) and idled the engine until the t-stat cycled several times, adding additional coolant each time.

It did it again today, I shut the car off just before the gauge got to the max and sat there and let the fan run for a minute or so(non a/c car), started it back up and then right away the t-stat popped and the temp shot down and it ran normal all the way back home. Water pump belt is only a couple years old but I'll check it again for tightness. Reservoir seems to be working properly, I can clearly see the level moving up and down after driving it. Heat seems to be fine on it, tho not as good as my parents daytona. I know that at least twice before in the car's life it's had stop-leak dumped in the cooling system, so I'm sure that's no help in keeping temps down.

If I put it back up on the ramps and am able to purge more air out of the system again, then I take it it's a guarantie it's sucking in air somewhere?

[looneytuner]

Keep checking it. Minor head gasket leak or sucking air somewhere. If you ignore it, the head gasket WILL go bad. The 1/16 hole in the thermostat will take care of the air buildup. For now snug down all the clamps. Some don't like to be reused.

[magtec]

assuming the car has a heater control valve, does the temperature stabilize if you switch to recirc mode?

[daytonaturbo87]

One thing, why could a plugged heater core cause the engine to overheat? On my satellite(440ci engine) I just plugged the feed lines going to the leaking heater core and no problems. I don't understand why a lack of flow could possibly make the engine overheat?! I work real close to home, so I can limp it back and forth to work quick enough that the engine doesn't have enough time to get above the 3/4 mark on the temp gauge. I picked up some new coolant and some coolant flush, I'll try it sunday, check clamps, purge, see if it helps. If it is the HG, hopefully I can limp it along for another week when I'll have time to fix it.

[daytonaturbo87]

assuming the car has a heater control valve, does the temperature stabilize if you switch to recirc mode?

non a/c car so no valve. Tho the heat seems to build up a bit slower if I have the heat/fan cranked to max.

[boost geek]

The engine had stop-leak dumped in it at least twice? Now I'm almost positive it's the heater core. If that simple circuit is clogged, the temp gauge will go max hot, then drop a bit, then max hot again, and keep repeating itself. A blown head gasket is only a short ways away. As post 5 states, you can bypass the heater, joining the 2 hoses together, NOT blocking them shut, and see what your temp does. If it runs cool again, buy a new heater core. Also feel the radiator for cool spots, could also be partly clogged from the stop-leak. Never, ever, use that crap in a turbo dodge.

[daytonaturbo87]

Well I ran the coolant flush thru it like the instructions on the bottle said and then filled it up with new coolant. Drilled the hole in the t-stat and checked/tightened all clamps, purged the air from the system. See what happens. If/when it starts overheating again I'll just bypass the heater core to see if that makes a difference. Thanks for the help so far. One thing I have noticed already is the temp gauge doesn't swing back and forth thru 1/4 of the range anymore like it was doing before the flush. Hopefully that's a good sign.

[boost geek]

Feel for cool spots on the rad. I had to replace the heater core and rad because the previous owner used too much stop leak. Headgasket blew also...