headgaskets maybe?

[cato421]

not sure if this is the problem but I think it might be, the car has been intermittently overheating in traffic, sometimes good sometimes bad. then today on my way home after slowing down at a light it started running really rough, no coolant in the oil that I can see, no smoke from tailpipe either. the odd thing is sometimes the idle will clear up, and as I was on the way home I had to drive it the rest of the way, it only seems to miss at or near idle. anyone have any thoughts or suggestions?

[cdru]

Are you losing coolant? If you have a head gasket leak, one or more things will happen. (1) Coolant will leak down the side of the engine, either dripping on the ground or evaporating if the engine is hot enough. (2) Coolant will leak into the cylinder, (3) Air will get "injected" into the coolant.

In the case of 1 or 2, you will have a noticable decrease in coolant levels. How quickly it drops depends on how bad the leak is. This can also be mistaken for a bad intake gasket as the latter is more common but the former seems to happen a lot too. Unless the coolant level drops quite a bit, it shouldn't overheat. You don't mention that the coolant level light has lit so this may or may not be your problem.

#3 happened to me this spring. Air/fuel from the compression and/or explosion was being forced into my coolant. This would cause an airbubble. Air doesn't cool like coolant which would cause my tempature guage to quickly go from normal to overheating (or vice versa) depending on where the air bubble in the system was at. It also forced a lot of coolant into the resevioir, eventually overflowing it. It started off just as a minor problem where revving the engine would "solve" the overheating problem but then it got bad enough that only turning off the car/bleeding the air with the bleeder screw would cool it down to limp home.

[Vtecguy]

IT sounds like #3 had happened to my 1998 Venture. What did you end up doing to your Van?

[cdru]

Head gasket. See this thread for details. The gasket doesn't require a PhD in automotive repair to do correctly, there is just a lot of work to get to it. Total cost when I did it was probably less then $300 after all was said and done. Shop cost probably would be at least 5x that.