'99 Montana Overheating

[wilkerson3]

My engine will overheat halfway on my dash's gauge, but when I drive 45 or faster on the highway the temp drops to normal. Gauge registers half-way when I drive in town slowly. Fan's kick on, but don't change temp, have newer (6 months) thermostat and water pump. Any suggestions?

[rkvons]

Your radiator could be gummed up and flow through it restricted. Also, how's your oil consumption and do you have to add coolant to it often?

[mcmalloy]

have you flushed the cooling system, if it had that orange colored antifreeze it probly started plugging up the cooling ports in the head gaskets

[wilkerson3]

Rkvons,
I'll try flushing radiator. Oil and coolant consumption? I have to add a quart of oil every 10-15K miles or so (adding small amount in between changes). Coolant - I add a small amount to radiator every so often (haven't paid attention to how often - maybe twice in last 8 months have added a third of a mix jug of coolant.)

McMalloy,
I had my brother-in-law help work on the van about 4 years ago (I don't know much about cars). We flushed the radiator of the orange coolant and not knowing any better replaced with green coolant. Flushed out orange coolant all the way.

Anything else I should work on besides flushing radiator?

[wilkerson3]

I was driving today and forgot to mention that my oil level light has been coming on (occasionally). The oil level is not low. Could this be reflecting a low pressure for the oil or signal my head gaskets are losing pressure?

[rkvons]

wilkerson3,

I am not an expert. I may actually be having a similar problem with my '98 Montana. The reason I asked about oil consumption is that if you have a head gasket leak, your engine could overheat. Heat gasket leaks usually have some kind of fluid leak that goes with them. I was towing a waverunner over the weekend, going about 70MPH, with the air on and I noticed the temperature higher than I usually see it under those circumstances. I've heard that the radiators can get clogged up over time if a tiny amount of motor oil is leaking into your cooling system. I would start the vehicle and let it run in the driveway for a while and see how hot it gets and when the fans turn on. After the fans have kicked on, I would feel the air being blown off and see if heat is coming off the whole radiator, or just part of it. Also, there is a bleeder valve at the thermostat that is used to get rid of trapped air. You might have some in there. Also, does your system seem to pressurize when it heats up?

[rkvons]

Originally Posted by wilkerson3

I was driving today and forgot to mention that my oil level light has been coming on (occasionally). The oil level is not low. Could this be reflecting a low pressure for the oil or signal my head gaskets are losing pressure?

I would change the oil pressure sending unit. I don't think it can be related to anything with the head gaskets.

[wilkerson3]

Pressure build up? yes. It build's up pressure and we have bled both bleeder valves (actually did three different times on different occasions). Thanks for the suggestions and we'll see what happens.

[rkvons]

Originally Posted by wilkerson3

Pressure build up? yes. It build's up pressure and we have bled both bleeder valves (actually did three different times on different occasions). Thanks for the suggestions and we'll see what happens.

Are you saying that air keeps forming in the system after you get it all out? This is a sign of a head gasket leak. The ignition occurs in the cylinder and the exhaust gas goes into the cooling system. You can get your coolant checked for the presence of combustion materials.

[wilkerson3]

I mean to say we have bled the valves two times, but the second time there was no air. Since we have started this thread (the last three days) the power in my engine getting weaker. I think my head gaskets are going. If I am driving on the highway at 65 and then push the gas to get into overdrive while climbing a hill, I can feel the energy not being contained. If I push harder on the gas it seems like the engine can't contain the energy, like it's leaking out. Van has 200K+ miles and so it may be time to retire her.