Overheating and Misfiring...

[groundhogday1976]

Hi. Haven't been on the site in a long time. Looks like a lot's changed around here. Anyway, my '93 240 has developed an overheating problem. I was losing coolant and traced the leak to the water pump. I replaced it, and while I was at it put in a new thermostat, coolant, radiator cap, and coolant temp sensor. It's no longer losing coolant, steaming, or anything but the temp. is still getting pretty high while driving. I can start the car and let it idle up to operating temp., and it stays normal as long as it's running, but as soon as I start driving it will begin getting hot. In the midst of this, the engine seems to be missing or dropping a cylinder. Don't know if the two are related and haven't checked plugs or anything like that yet. Thanks for any advice.

[Eikon]

Did you properly bleed the air out of the coolant system after you replaced all those things? It could be an air pocket that hampering the proper function of the cooling system.

One idea might be to yank the thermostat back out. Put things back together and run the car with no thermostat. If the temp stays low, then you have a bad t-stat or imporperly installed... If the temp still goes high, then you may have other issues...

Do you get heat in the cabin after the car has warmed up? If you do get good heat, at least you know that the coolant is circulating as it should.

[groundhogday1976]

I left the burp hole open until air bubbles started coming out, but I guess it's still possible for air to get trapped. The heater is working. It seems like trapped air is the most reasonable explaination, since I don't have any more leaks and there's no boiling or anything.

[180fan]

A tip for bleeding air out is the have the front lifted on some ramps or have it parked on an incline, have the heater on HOT and pour through the radiator with the bleeder hole open until you get coolant out of that hole. Cap the bleeder, then keep filling till you get coolant out the top. cap the radiator and squeeze the upper and lower radiator hoses for a minute and undo the cap and top off again. Do this till you can't pack in any more then start the car and keep squeezing the hoses, have this going for about 30 seconds or so and let it cool off. Get a beer and get back to work. Repeat till all is good and your coolant levels go nowhere. then keep a small bottle of coolant around and after you drive a bit, let it cool off and top off some more.

[groundhogday1976]

I just thought of something I failed to mention. Some time ago, my fan clutch seized up and somehow the fan shroud got a 1-1.5" wide slot cut along the entire length of the top of it. Could this be a problem?

[180fan]

it could contribute but doubt it'll cause an overheat.

[groundhogday1976]

Well, I spent quite a bit of time making sure all the air was bled Friday, but I'm still having the same problem. It'll idle up to operating temp, then get no hotter even if it sits there for half an hour, but then if I start driving it starts to overheat within a mile. I don't know what I'm doing wrong. I've changed the water pump and heater core before and never had this much trouble after replacing all the coolant. I replaced the O2 sensor since it had been quite some time since I had changed it, and that seemed to get rid of the missing.