Question : Blown Head Gasket? '88 2.8L

[HJR1]

Hey all, been a while. Hope you can help me out here. About 2 years ago I put an '88 2.8L with just under 80K in my '87 S15. I installed a new radiator, water pump, T-stat, and radiator cap on it. Have put a little over 5K miles on it since. Never had the slightest problem with cooling. It was perfect, you could even watch the t-stat open in the morning via the temp gauge. Got to where I'd know where I would be when it opens.

Last week I took a short road trip, 80 miles total, 40 there, 40 back. 110 degrees out, A/C on, 65-70mph. No problem out, no problem most of the way back, right before getting home the temp gauge suddenly started climbing. 260 is as high as it reads before it pegs. It got to the 260, but did not peg. Engine had none of the symptoms of a seriously overheated engine, knocking, loss of power, etc. Pulled off the highway and popped the hood. No leaks, but it was pushing coolant out of the overflow.

At this point the only thing in the cooling system that wasn't new was the fan clutch. I wasn't optimistic of this being the problem, but since it did have some wobble in the bearing it didn't hurt to replace it anyway, so I did.

Would still run hot, but it was intermittent, I could drive for a while with no problem, t-stat would open like it should, everything would be fine then it'd start heating up fast.

Out of desperation I replaced the t-stat and radiator cap again. Odd thing is, I left the truck idling for nearly an hour with the A/C on and it never got hot. Stayed right where it should. Both upper and lower radiator hoses yielded to my squeeze.

Took it for a drive the next day, at first it was okay, but then it suddenly got hot again. Pushed coolant out the overflow again. Both upper and lower hose were under quite a bit of pressure. Even when it wasn't loosing coolant, but just running warm.

So, earlier today I had it running with the hood up. Noticed it had a miss, uh-oh, found out the #5 wasn't firing. Pulled the plug, it was wet.

No oil in water, no water in oil, no smoke or sweet smell out the exhaust. Is it possible to blow a head gasket just enough to pressurize the cooling system to the point it blows coolant? And that's all it does?

I have some pictures here of the plug, sorry they are very, very poor quality, but you can see the coloring anyway, does it look like it's been burning coolant? And I don't know if it's related, but you can almost see in that last pic that there's a chunk missing out of the porcelain.

Sorry so long, wanted you to have all the details, thanks in advance for any help.

No blockage in front of the radiator, timing is spot on 10 degrees. Put a compression tester on #5, 180lbs hot.

[pocket-rocket]

I've had 2 vehicles come to me blowing coolant while overheating. The other symptom was no heat from the heater. It was a head gasket allowing compression pressure to escape the cylinder into the cooling system in both cases.

I would go to the nearest parts store chain and rent a cooling system pressure tester. Both vehicles held fine when cold but held like a sieve when hot. Hope this helps.

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[HJR1]

Yeah, I have one of those pressure testers, I'll give it a shot, but it sounds like I have to prepare myself for doing the heads.

Here's a better pic of that spark plug:

[HJR1]

Ugg, just confirmed the bad head gasket. Left the radiator cap off, removed the #5 plug, hooked up the air compressor to the hole, charged it with 120psi, coolant flowed out the radiator......

Got a head set on the way.

[geoffinbc]

On the iron heads you need to carefully inspect the area between the valves for cracks. It is more common than a blown gasket. However in either case be sure you put a straight edge on the block and the head your installing. Straightness needs to be less than .002" with a feeler gauge.

[HJR1]

Okay, I'll check it closely, but even if there is a crack at the valves would that pressurize the cooling system?

[pocket-rocket]

It could if the crack was deep enough to penetrate the cooling jacket.

As a rule of thumb I try to get who's ever car I'm working on to allow me to have the heads cleaned and pressure tested at the machine shop before reassembly to avoid using a head I couldn't detect a problem with. To me, $80 is cheap insurance against putting a junk head back on.

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[HJR1]

Well, it looks like I lucked out, to a degree. I just pulled the head and you can see the gasket failure. That metal ring around the cylinder has a smaller metal ring in it, almost a wire. The metal ring was broken and didn't complete the circle, it actually penetrated the combustion chamber. The wire inside didn't brake and completed the seal. You can see two patterns on the head and block surface, the circle of the small wire, and the broken ring. Looks like the wire did the job of sealing until it couldn't anymore. On a low mileaged engine all I can figure is either the head gasket was flawed, or it was damaged when installed.

[trotterlg]

Could have been bent there, you should clean it up really well and lay a straight edge across it to make sure it isn't warped and to check that the blown gasket didn't cut any of the head or block. You will probalby be good though, it takes a while to do much damage. Larry