I’d spotted a little coolant weeping from pass/rear head a few months ago.

Started running no pressure cooling system which stopped that.

Now I’ve discovered a coolant explosion inside engine bay, after a mild overheat (UG read 205) which was suspicious, as I never get that hot.

Now it’s starting to overheat at 1500 rpm standing in the driveway.

Rear of the same head looks to be wet again, although could have been from the coolant from the cap.

Is there ANY chance it isn’t the HG?

Anything I can do before committing to that?

Edit. 145k. Had it since 90k, HGs never done.

Edit2. Slight coolant drop from water pump, but not the weephole. So I don’t suspect that failed. And coolant is moving around the system.

 

Describe the coolant explosion location, you can also get an exhaust gas test kit which will tell you if you exhaust gases in the coolant.

Things to check:
Moisture coming out of the exhaust or thick white smoke.
Rock hard hoses
Rad does not get hot

So you have a couple of possible issues :

• Bad hoses /Plugged rad - this is dependent on where the "coolant explosion was"
• Water pump is shot - moisture around the water pump is never good it is almost always a dead seal
• Head gasket is gone at the rear of the passenger side, externally and internally. Note this should not cause a huge overheat in most cases at idle or moving.
• worse case cracked block, this will generally cause a pretty significant overheat no matter what

 

Coolant came from filler cap.

So I guessed that combustion gases are entering coolant. I can go get a test kit for that this afternoon.

It took about half a gallon to refil.

When I run it and watch I just see the temp climb. But not push out of the cap.

I noticed 205deg on the UG. Temps are usually 180-190’s.

No smoke from the back.

Hoses not rock hard. (Remember it’s running unpressured at the moment.)
Didnt check rad temp.

Water pump has what looks like a small gasket leak, ive been monitoring it for months.

There has been coolant from rear of passenger head in the past. I’d cleaned the area and was watching, nothing, then this.

Does it need tearing down to find cracked block?

I have a call in to Carlos at British Auto Works in the Bronx. They have an acceptable price to do HG and everything involved with that.

 

@cappedup It is pretty tough to find a cracked block, but given your head gasket leaked under pressure it is a fair place to start with the head gasket.

 

You can put the system under pressure and you might find the seepage in a cylinder, can you borescope the cylinder? Better if you can do it hot.

 

Is it blowing white smoke?

That's literally the biggest giveaway.

If not, you're fine.

 

Not blowing white smoke.

And, couldn't get the blue fluid test to show positive either.

BUT, there is definite coolant seepage at the back of that head. Along with overheating.

I feel like I have to take it for a drive and see what it does.

 

Hmm, possibly yes. You think I might see evidence of the coolant inside the cylinder? Check the one closest to where I see coolant on the outside? I have one of those things that you stick in your ears to check for wax, connects to your phone. Great tool for those wanting to scrape their own ears BTW. And we all arn't getting younger.

I can also check to see if that plug is steam cleaned, compared to the rest I guess.

 

They don't always blow white smoke if the leak is small. They don't always fail the combustion gas test. And they don't always fail a pressure test. But a pressure test is a good test. I had one that blew a head gasket, slight blow, not big. No white smoke, no combustion gas, but an overnight pressure test failed and it put enough coolant in the cylinder to hydrolock it - had to remove the spark plug to get it to turn over. Had another one crack a cylinder, put a teaspoon of coolant in the cylinder from a pressure test that we could see. IMO pressure test is the best test. And yes with a bore scope you can typically see the one cylinder is much cleaner on the piston top if the hg is blown.

 

Frustrating day.

Now can’t get it to overheat.

Although is spitting some coolant from the bottle overflow.

Blue dye test still good.

My boroscope wasn’t good enough to see anything, although the plug in the suspect cylinder is fine.

Still a little evidence of coolant at rear of pass head.

I’m next going to try pressurizing the system and see if that ‘finds’ anything.