Head gasket or head?
 

Well, my 3RZ swap has developed a hiccup. It lasted flawlessly for about 75K miles. But...

I was on the way home to Tennessee from Miami. Around Orlando it started to get warm on the gauge. By the time I got off at an exit and checked the coolant level, it was hot. 220* according to the OBDII scanner. But I popped the cap, and it took a whole half a quart... Coolant temp went back to normal and I drove on home. That was two weeks ago. Then a couple days ago, I had driven an hour to check out moms car, and on the way home it got hot again. Limped it home, never getting more than 215* on the scan tool. Popped the cap today and put in a quart of coolant. When I started it up, I got a good deal of pressure and started spewing coolant back out. And I smell fumes in the radiator, almost exhaust smelling, along with a steady stream of steam.

So, I'm sure we have a head gasket/head issue. Any thoughts before I take it off? I wondered about doing a re-torque of the head bolts, just to see what that would do. Thoughts?

I will take it apart anyway, since I want to do an MLS head gasket and finally install the ARP studs for the head...

Sorry to hear that. Really only way to know is pull the head and see if it's cracked or just the head gasket let go.

I was sorry to find it out. Lol. Any thoughts as to why it may have let go?

I will try and get it apart tomorrow. Not in a massive hurry yet though. The wife's '88 Runner will be here Thursday and I finally get to start her 3.4 swap. Yay!

Took the head off this morn, only took a couple hours, and drove it 45 min to the machine shop. I will pick it up in the AM. He said no cracks, and everything looks ok. He shaved a smidge off, nothing drastic. Gasket was blown between #3 & #4 cylinders. And from cylinder 4 to a nearby water jacket via the head gasket. No coolant/oil mixing, no coolant in the cylinder. Cylinders look awesome, crosshatch still flawless. A little bit of carbon on a couple spots of the pistons, but all cleaned up now. Head studs and new gasket set hopefully going in tomorrow. I will post final outcome.

Sounds like you're on it. Pretty rare for one of these to pop a gasket. Mileage?

Approximately 75K since the rebuild when it was swapped. But the machine shop re-used the TTY (torque to yield) bolts, so I'm hoping that was the root cause. When I loosened the head bolts, there were a few that were significantly tighter than the others. I'm thinking the several "looser" bolts allowed uneven clamping pressure and allowed the gasket to fail. I was going to do an MLS head gasket, but that requires the block and head to be accurately machined, and I didn't want to pull the block for that.

I had the ARP head studs for the rebuild, but I didn't get them from LCE by the time the machine shop put it back together... So I saved them, and they're going in now.

Well, I replaced the head gasket, used ARP studs, tightened them down in 7 steps going up to 80lbs-ft. Everything went back together great. But it still has excessive pressure coming from the radiator and overheating. So a new head gasket and studs didn't fix it. Machine shop said it checked out fine, no cracks found. So what am I missing?

Is it likely that the machine shop didn't check it well for cracks? I certainly didn't see any. They did machine the head a few thousandths, saying it didn't need hardly any removed.

What else could cause overheating, excessive pressure in cooling system, but no oil/coolant mixing?

Did you check the mating surface on the block with a straight edge and feeler gauge?

If they machined it then they probably pressure checked it for leaks. If compression is good and no water leaks I don't think it's a head. Could a previous owner have used a bars-leak type product and you just had a piece break off and plug a cooling passage or at least partially? Just guessing. Really weird problem. Did you put a high flow water pump on? ( do they even exist?). Just guessing. Keep us posted on what you find out. Good luck.

I did check the block while it was in the truck. It appeared flat from any direction I tried to get a feeler gauge under.

And there has been no Stop-leak put in this engine. With the swap it was completely rebuilt, new radiator, etc.

I'm gonna have to guess the head is cracked somewhere...