Overheating - Plenum Gasket?

[kamspy]

My Bonny just started overheating out of the blue.

There is no visible coolant loss.

There is moisture around the water pump, but I haven't had a single drip onto cardboard.

When the car overheats, the majority of the steam comes from the belt area. (well, that's the way it looks at least)

The radiator is completely cool during overheating as well. Hose going into thermostat doesn't seem to have any pressure at any time.

I have replaced the thermostat since this started.

The water pump's seems to be firm when tugged on, so the bearing appear to be O.K.

I did skip the AC compressor with my new belt, but it ran just fine for months after that.

Also, just to get everything out there, the fans inside the car stopped working and all fuses are good. Not sure how to check the relays 'block' fuses.

From what I've read, these cars have problems with the plenum gasket leading to coolant being mixed with the oil. I only checked the dipstick, but it looked like oil. I am using Dex-Cool (the orange stuff) so I'm guessing it wouldn't be apparent anyways.






Thanks to all the guys here who helped me with my last problem (cam sensor, ICM nightmare- turned out to be a fuel pump )

You guys are top shelf!

[willwren]

DEX is the worst thing you could have introduced into your system.

http://www.dex-cool.net

Your actual problem however, indicates a lack of flow. Either the thermostat is stuck closed, the water pump isn't spinning INTERNALLY, or you have a sever blockage in the system. DEX is known to produce sludge, especially when mixed with traditional glycol (green) antifreeze, or put into a 'green' system that hasn't been totally flushed.

Ultimately, you need to find out where that leak is really coming from (likely the water pump) and pull that part for an investigation. In addition, I would suggest replacing your LIM gaskets and flushing every last trace of DEX out of the car.

You can test your thermostat in a boiling pot of water, which will also give you an opportunity to see if there's any sludge blocking that particular part of your cooling system.

Make sure when you bypassed your AC that you actually have the water pump spinning the right direction as well.

With the thermostat housing and thermostat removed, start the car. Coolant should come out of the thermostat pocket in the LIM if you have any flow.

[kamspy]

OK. I didn't do a complete flush before introducing the DEX. Big mistake I guess. I'd assume I still had about 25% green in there when I topped off the rest with dex.

It has been around 3 months since I did that.

The thermostat was the first thing I changed since the overheating started. No luck there.

I'll try starting it up with the therm housing and therm taken out.

Now to find somewhere to flush that Dex out. Last time when I flushed out the green (most of it at least) we ran out of buckets.


Thanks for the tip.

EDIT:

Great read on Dex-Cool. Nasty stuff.

[bill buttermore]

When Dex is mixed with the older style green phosphate coolant, a slimy brown sludge is produced that is capable of blocking flow to the radiator or heater core. willwren's advice is spot-on. As he suggested, flush the system to get rid of ALL of the Dex. Here is how to do a thorough job of flushing: Reverse Flush your Cooling System

[willwren]

In many cases, the radiator may be a total loss. It may not be possible to de-sludge it using traditional means.

[imidazol97]

Having no pressure buildup says there's a leak somewhere that's venting any pressure. Is the underside of the radiator cap gunked up keeping the small disc from sealing to allow pressure to build up?

You should be able to locate where the steam is coming from.

How does the water pump feel when you turn it with the belt off? Do you feel the impeller pushing water when you spin it fast?

Did you find any evidence of sludging when you remove the thermostat housing? Looked into the radiator with a flashlight?

Is the upper radiator hose warming up?

Is heat coming out of the heater? That would indicate water is circulating through it. That could mean the water pump is pushing water okay.

Have you opened the water pump to see if the impeller is okay?
Is there a leak at the intake manifold where a plastic fitting screws into it and hose connects to the water pump? Those crack and leak. There was a replacement that was metal issued. (Why didn't GM learn from that plastic experience and avoid the plastic uppers they went to on the Series II?)

Here's an article on flushing DexCool because of sludging... It's written for a 4.3 motor but it's from GM and indicates how serious removing the sludge, if present, can be.
http://members.shaw.ca/betterthanyoutoo ... lflush.htm

[kamspy]

Having no pressure buildup says there's a leak somewhere that's venting any pressure. Is the underside of the radiator cap gunked up keeping the small disc from sealing to allow pressure to build up?

Radiator cap and everything visible inside looked clean.

You should be able to locate where the steam is coming from.

Yesterday it was very distinctly coming from the valve covers. Today it came from the belt area. No valve cover action at all.

How does the water pump feel when you turn it with the belt off? Do you feel the impeller pushing water when you spin it fast?

Didn't take the belt off, but when it went out a couple years ago I could feel 'play' in it with the belt on.

Did you find any evidence of sludging when you remove the thermostat housing? Looked into the radiator with a flashlight?

Thermostat looked like this:


The radiator appeared clean. Good daylight, but no flashlight.

Is the upper radiator hose warming up?

Yes. But no pressure.

Is heat coming out of the heater? That would indicate water is circulating through it. That could mean the water pump is pushing water okay.

Hard to tell. My interior climate control fans stopped working a month ago.

Have you opened the water pump to see if the impeller is okay?

Haven't taken the pump off yet. Have to take the engine off the mount to get to it. Hoping to avoid that, not looking like I will be able to.

[willwren]

You've got some work to do. Let us know when you've properly diagnosed your water pump, and verified you actually have good flow through the system.

[93RedSled-SSE]

There's one other place for a leak near your pump; a bypass that comes out of the end of the lower intake above the pump. It is not uncommon for one of these to crack/break.

The post below was a case of the impeller shaft breaking inside the pump. You share many, if not all, of the symptoms. This isn't real common, as far as I know. Ugly Pictures on page 3
http://www.pontiacbonnevilleclub.com/fo ... 3&start=40