Coolant Issues/ Blown HG?

[zero_wheeler]

I was doing some spirited driving last weekend. I was about an hour away from home and I noticed coolant temps we're rising. Pulled off to the side, let it cool down and checked the coolant. Radiator was bone dry. Filled up back up and limped the hour drive back home. Upon getting back into the driveway, I noticed temps climbing again. The next morning I checked the coolant again, bone dry. Also when driving back the car sounded strange, Almost like a Subaru. It wasn't quite misfiring, it just sounded off. Naturally I did some digging.

The car isn't leaking coolant anywhere, so it has to be burning it. Which leads me to guess the head gaskets done. Tried some of the usual tests and came back with some off results.

-No coolant in the oil
-No abnormal smoke out the exhaust
-No sweet smelly smells.

So I figured, hell, compression test.

1- 160 psi
2- 172
3- 160
4- 158
5- 148
6- 149

Now i'm a bit stumped. Compression across the board doesn't look TOO off. The random 172 was kind of eh? but other than that for a 20 year old car I don't think the HG should be giving it the problems it's having. Then I read a post on an old thread from a "Seasoned" member saying something about how it's somewhat common when the head overheats and warps, the back side near the 5th and 6th cyl warp first, crushing the HG.

So my question is, Do you think the lower compression on the last two cyl are enough evidence to pull the head, Or could my problem be somewhere else?

I've got most of the parts ready to start my top end rebuild and turbo swap, but not quite all of them. I'd rather wait a couple weeks to obtain the rest of the parts, than replace the HG now. Two birds one stone right?

Sorry for the essay! Any suggestions/criticism welcome.

[nimblestix]

Sounds like a head gasket to me. Comp numbers are a little worry some, but if the gasket is done those numbers don't really help determine the health of the engine, aside from showing its leaking.

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[Skym]

Thermostat late opening if coolant level is dropping in radiator. When engine is up to temp (above where thermostat should start to open), put hand on lower radiator hose and then put hand on top radiator hose. If bottom radiator hose is very cold vs top that is warm or hot, thermostat is late opening.

Compression looks within specs (maybe a bit low in 5th, 6th). I think (from memory) it was below roughly 128psi = rebuild. It can vary 8-10psi or so between cylinders and still be within spec.

I would be looking into skimming head, fitting a metal headgasket (Tomei or similar gasket kit) in the future (like you have planned). Or maybe a cheap rebuild / refresh if can afford it (if engine has done over 100,000km, which is the recommended rebuild / refresh km).

[zero_wheeler]

Thanks for the quick response.
After flipping through some old threads, I'm just going to pull the head tomorrow morning. It's the first time I've done it so i'm starting early.
I'll be sure to post my results.
I suppose my top end rebuild will just have to wait.

[zero_wheeler]

Pulled the head this morning..





Head isn't warped, Gasket shows pretty bad fails on the #6 water jackets. #5 was getting there, but not near as bad. Glad I caught it somewhat early.

holy hell getting those turbos off was a b!tch!..

Any tips for the new HG? Sealant? ect?

[h4X6]

Cometic metal head gasket

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[zero_wheeler]

I've got an HKS metal one, with some ARP studs.

[Skym]

Head isn't warped, Gasket shows pretty bad fails on the #6 water jackets. #5 was getting there, but not near as bad. Glad I caught it somewhat early.

holy hell getting those turbos off was a b!tch!..

Any tips for the new HG? Sealant? ect?

That's good to hear. Explains the coolant loss. Pressure testing cooling system via radiator cap might have picked up the internal leak (pressure drops).

Get head pressure tested for leaking valves or valve seats and check valve guides for cracking and get check head for cracks. Best to replace exhaust manifold, intake manifold studs with new studs from Nissan while head is out (they can snap when refitting parts). A cylinder head shop should be able to do this for you.