3rzfe headgasket or cracked head?

Hey guys, my 97 4runner 3rzfe is giving me problems. I have 135-140 psi on cyls 3,4 but about 15 on 1,2.

Barring the Engine over I can see the valve shims going down and returning up for both cyls. Cant see theres an issue there.

With 1,2 valves closed I can put shop air to either 1 or 2 and I'm getting what I beleive to be pretty much equalized pressure. But I can also it hear it significantly coming from the exhaust

Obviously Ill need to pull the head but for those of you knowledgable on this eng what sounds most likely? Cracked head or blown gasket? Or???

No pressure to the cooling system though.

Any thoughts are appreciated. Ill be tearing it down regardless but just kind of frustrated and wanted some opionions either way.
Thanks

 

Has it overheated? Heads don’t usually warp on their own. What kind of history does it have? A little more info might help.

 

They will crack though. This guy got one without overheating.



I found similar cracks in two heads off a 5vz. I think these engines are prone over time to do that. Can't complain for the years of service. Most cracks I've seen on these (well 5vz's) are in between the valves and small enough that they are hard to see.

 

I rebuilt it about 15 or 20k ago. Head was checked out and good to go. I bought it used knowing it had eng problems. Someone stuck a piston so I suspect it was overheated.

Ive not had any issues but a cracked exhaust manifold since the rebuild.

I'll get the head pulled off and see what I can find but I just can't imagine how that much could bypass between the cylinders.

I tried plugging 2 and 1 still had low compression and vice versa.

With shop air to 1 and plugging 2 I get a tiny bit out of 3 and a lot out exhaust.

 

Sounds like burnt exhaust valves. If the valves have been run tight, the heat of combustion will burn the valve seat and backside of the valve. This will cause sealing issues you are describing. Depending on the condition you can lap the valves back in or if they are bad get new seats and valves.

 

3rz’s are well known for burning valves too if the gap isn’t checked periodically. I’ve seen 60k mile recommendations, but to me that’s a bit soon. I plan to pull mine when it hits 100k, check valve lash while doing timing chain, water pump, etc.

 

Would make sense. I usually try to take it easy on this thing but I was trying to catch my coworker before he left to let me back into the shop to grab my phone so I turned around and hauled ass back, rowing through the gears with that 2.7 power. Got headed home a little later and got half way there and it started making some weird rattling not like a rod knock. Went to pull it into the garage and it was barely idling.

Ill let you know what I find.

 

Blown head gasket between 1,2

 

How did the head check out for flatness on the mating surface?

 

The first time? Good. This time? Idk yet. Gotta have it checked still.

 

And the head is junk. Several cracks between the seats.

I kinda figured thatd be the case. Wah wah wah