Erratic high idle and coolant boiling

[Yellow Stealth]

My car was running fine until recently. the only thing that has changed recently is that the dealer changed my spark plugs as well as spark plug wires.

I had always had a little bit of coolant come out of the overflow after driving the car for a while. One night, it dumped large amounts of coolant from the overflow and it sounded like the water was boiling in the overflow tank.

I did some searches on this site and determined the seal on my radiator cap was damaged and got a new one. That seemed to fix the problem for a little while.

However, my idle now started being erratic. Instead of the normal 800rpm or so, it sits at 1500 or sometimes even 2000rpm, rarely going back down to normal levels.

After shutting my car down last night, I heard some serious boiling noises again coming from the overflow tank (but no coolant was leaking onto the ground). There was also a loud squealing noise from somewhere below the overflow tank. What do you think the squealing was from? Remember the engine was shut off at that point.

Any idea if these two problems are related? Any idea what could cause those?

[aussie_will]

Have you replaced your thermostat?

[Yellow Stealth]

Originally Posted by aussie_will

Have you replaced your thermostat?

No, I have not tried that yet. Would it also explain the idle problem? Is it easy to replace?

[DCIV]

sounds like compression test is in order. Which way is the overflow hose pointed? Does it go down next to the header where it could make that noise? It prob just Tstat but most dont complain about their overflow tank spraying everywhere.


Coop

[keithmac]

Change the thermostat, check the radiator fans are coming on when they should / or at all.. Get a sniff test on your header tank to see if there`s exhaust gas in there, if you`ve been losing coolant and overheating for a while your head gaskets are more than likely toast..