car overheats

[unreal808]

Sorry about the relay thing, a relay either works or not. I was thinking the fan my not be coming on sometime.

[john]

We are bringing it in to a cooling and a/c place on monday to have them figure it out. They said they could figure it out.

[john]

All this posting is not me. It is slowbubble car too lazy to log out.

[john]

Ok, I looked at the car for a few minutes tonight. I started it up and let it run with the radiator cap off. After 10 minutes, the car was still right in the center of the gauge. I sat the car at a constant rev for a little to warm it up more and I noticed that when I reved the car, the coolant level would lower in the water neck. When I let off the throttle, It would come up to the top and dump a little out. When the car was heated up more, I tried it and some white shit came up (possibly little bubbles) and some larger bubbles came out. This happened each time when the car was warmed up. After about 20 minutes, I shut the car off and the coolant, which was at the top of the water neck, dissapeared and was not visable anymore under the radiator cap.

My original guess was that the car has a warped head. Comp was 140-140-130-90. James blew coolant past the HG on a pull at 25psi. My guess is that when the car heats up, air is sucked into the coolant passages by the HG. The car has ARPs torqued correctly and blew coolant on the second pull. Any second opinions???

[Wizard]

Actually air is pushed into the coolany passages, not sucked. 140psi compared to 13psi.....

And it's actually quite common for a DSM to blow a headgasket like that. Considering your compression numbers, I would doubt that the head needs to come off, shaved a touch and new gasket.

Another way to verify this:
With a good radiator cap, fill the rad neck full when cold. Fill the overflow to low mark. Drive the car for a couple days. Then when it's cold again, if the overflow is full, but rad. neck low or empty.....HG.

Wiz

[JET]

If that head gasket is blown it will cause it to overheat. Another possibility is the thermostat, get a real mitsu one. I have gotten several new ones from regular parts stores that were junk when new. The last thing would be a new radiator cap. If those 2 don't do it, then it is probably the HG.

[slowbubblecar]

So you don't think the car needs a new HG? It was tuned fine and on the second pull blew out with 1.83 counts of knock. We tightened the headstuds a little and it held on the same boost and tune. I am pretty sure the neck gets lower, but the overflow stays the same level but we will check again.

[slowbubblecar]

I will try to get another thermostat and I will try another radiator cap tonight.
Thanks

[JET]

No, it is a good possibility that the HG is blown, but I would try the easy stuff first. No point in pulling off the head to find out the thermostat was bad!

[Wizard]

A bad thermostat only causes 2 things:

Overheat due to lack of flow (stuck closed or opens late)
Over cooling due to stuck open thermostat.

The water level going up and down when you rev it is a great indicator of a working water pump.

Air bubbles can only get from the headgasket. And other place where coolant would leak would be an external coolant leak. Not bubbles in the coolant.

Rad. cap is a possibility, BUT you said that you had the cap off and then started seeing bubbles. Kinda obvious in my book. A bad rad cap will cause the high overflow/low rad neck situation. Try that first, but I would expect a "blown" headgasket.

I call the other hg failure a "leaking" headgasket. That is where coolant is sucked into the cylinders and then burned. Hence, white smoke and miss. It also slips by the rings into the oil pan.

Wiz

[slowbubblecar]

I am pretty sure the HG is the problem. I might pull the thermostat out and drop it into boiling water to see if it opens to see if it is fine, but I am planning on replacing the HG anyways since it was blown out the 2ng pull. We torqued the head studs to 95 try to seal it again. It holds during boost, but I am guessing it still might be the problem. My brother said there was white stuff coming up with the filler cap off so I am pretty sure it is the HG. I am going to make sure the head isn't warped before I put it back on to make sure it isn't the reason it blew out in the first place. The car was tuned pretty good so I have no idea how it blew out in the first place.

[JET]

Just take the thermostat out and run it.

[MATCHBX]

Originally Posted by Wizard

Air bubbles can only get from the headgasket. And other place where coolant would leak would be an external coolant leak. Not bubbles in the coolant.

Wiz

This is not the only way air is introduced into the system. Granted he has a new waterpump on it, but if the seal goes out in the waterpump it will introduce all kinds of air into it with very minimal external leakage. The only leakage seen when the seal is bad (or the shaft of the pump is grooved) is after it's shutdown. And then it sometimes is only a tiny bit that doesn't make it all the way to the ground.

And it's not recommended to rev the engine with the cap off. The radiator cap is a two-way valve for that purpose. The system will push coolant past it at a set pressure. But when the thermostat opens, it draws coolant back into the system via the little poppet in the center. You can let it idle with the cap off, but use the techniques that Shane and those were talking about with the funnel to keep the level always above the engine so it is never starved for coolant.

I agree with Jet, eliminate the easy stuff first. Take out the thermostat and run it to see if it does the same thing. It could be that the thermostat sticks a little and then opens up, thus creating erratic readings. But it would probably be pushing the excess coolant out into the overflow. It could be just enough that it doesn't overflow out of the bottle before it gets sucked back in.

[slowbubblecar]

The car still overheats with no thermostat in it. What would you do? HG? I am pretty sure coolant gets sucked into the overflow bottle but doesn't get pulled back it.

[JET]

Yep, it sounds like a minor HG problem. As long as the radiator cap is sealing well and is good, then that is probably what it is.

[slowbubblecar]

Thanks