Bad head gasket or ?
 

Hey guys, I'm having some symptoms that I believe are indicative of a bad head gasket, but I'd like a sanity check.

First a little background. Early this spring I did a timing belt change complete with water pump. All was good for the first 50-100 miles until my water pump dumped all of my coolant out on the way home from a movie. I'm not sure exactly when it happened and how far I went in that state because I didn't notice the temp gauge until I pulled into my driveway. Anyways, I fixed the water pump and observed for signs of a bad head gasket but didn't see any. About the same time my turbo started making noise so I swapped it out for a used, but seemingly in good condition, T28.

Once I got the car back on the road I noticed a couple of periodic upward temperature swings, but thought that I just had a bubble stuck in the coolant passages. I flushed the coolant system and didn't have any issue on normal drives to and from work. However, whenever I do any spirited driving and get into much boost I'm finding that my coolant system is building a lot of pressure, to the point that I blew of a radiator hose. I'm also finding that in these instances I'm losing coolant and building up a lot of air in system.

My theory is that I do in fact have a failed head gasket, but that the failure is small enough that it's only apparent under boost. The only other possibility I can think of is that the used turbo is somehow introducing boost into the coolant. Unfortunately since I did the two fixes in short succession and didn't drive the car much in between my variables are confounded. Any ideas or experience? If it is the head gasket, it doesn't look like too much work to replace, but should I assume that the head will need to be machined or replaced? If I do, I'll evaluate potentially swapping in a used engine or maybe biting the bullet with a built engine, depending upon what I decide to do with the car longer term.

Thanks for your help.

I really don't see how the turbo could possibly pressurize the coolant. Its likely that either the head is cracked or the gasket is blown. I'd pull the head and at least have it checked at a machine shop, and of course replace the gasket.

Head gasket. Classic symptoms of it. Even if the CHRA is fractured there's no way to introduce boost into the coolant. The best it could do would be to dump coolant into the oil return.

Head gasket.

Head gasket. Your turbo is fine. Your head is probably warped though.

You've recited the classic "my coolant hose burst and I didn't notice right away" story. I've been there before, many of us have. This story usually ends with overheating (check) and head gasket problems (check). Which are of course caused by the head warping.

My guess is that you only mildly overheated your car and may not have permanently warped or cracked the head. It sounds like you had enough coolant in the engine for the temperature gauge to still function, which is a very good sign. I only noticed on my car when the oil temp gauge hit 300+, by which time the head was completely boned. Temp gauge continued reading normal the whole time because there was no coolant on it.

The thing is, you're going to have to remove the head to change the gasket, so you might as well get it looked at for warpage while you've got the head off. It's about 1% more work.

Thanks for the confirmation. Pulling the head will probably have to wait for the winter, but I'll keep my eyes open for a lower mileage used engine in the interim as I wouldn't mind freshening up one with lower mileage as a replacement.

What year engine/head do you currently have?

edit: 94 I see. Can your DIY MS control VVT?

I don't think it natively can, but can be modified to do so. I could be mistaken though as I haven't really looked into it closely. This could be an upgrade opportunity, but I'm also considering fixing the car and selling to move into something newer. Thanks for the idea though.

If I were smart, that's what I'd be doing.

Yea, I'm starting to feel like your username. My balance of free time vs money has started to shift to the latter and continually wrenching on the car is starting to get old.