It seems like a MLS head gasket can't exactly blow unless metal actually is lost. But when I removed my head gasket, all the material seemed there. On D series engines is a "blown" head gasket really just a warped head?

I have a D16Y8 with 200k miles on it that had exhaust gas getting into the water jacket, I replaced the head gasket and really nothing changed. I changed the head gasket again and put a junkyard head on it and it seems to be holding alright

The original head looks ok, and I used a straight edge and it seemed straight enough. Think the head is ok? Does it need a resurface at the machine shop?

 

Did you actually measure it or did you just eyeball it? What kind of straightedge?

 

kind of eye balled it. I used a long ruler and set it along it's thin edge, not the flat face, but the thin side of the ruler

 

Was the straight edge longer than the head itself?

Are you checking it per the FSM and using feeler gauges to verify how flat it is? One cannot simply eyeball it....

 

yes, it's longer than the head.

Not checking per the FSM And not using feeler gauges.

I'm just really wondering if the head warps on these D series engines and the head gasket doesn't actually "blow"

Has anyone just replaced their "blown" head gasket without resurfacing the head and everything is all good?

 

When you torque down the head, the gasket crushes and seals between the two mating surfaces.

If you don't resurface the head, the area where it has warped is still there. It will leak again, soon, if not right away, because it is not going to seal.

 

He didn't use a straight edge, he used a ruler.

 

We would always send heads out for checking, pressure test and milling, until one day we sent one down to the machine shop. They were really busy, they put a straight edge on it and sent it right back with our driver saying all good and no charge. After that we bought a straight edge(real deal in a wooden box) and out of the last maybe 100 head gaskets only sent out maybe 2 heads to the machine shop and that was just because the tech was paranoid and being extra cautious.

It it was run a long time with a bad gasket, or seriously overheated I'd pay close attention with the straight edge.

But in regards to your orig question, a machine shop could pressure test your original head. But that costs money, I wouldn't bother. Or just flip it on it's back and fill the chambers with atf yourself and see what happens. I'd probably just chuck it in the dumpster.

 

When you take apart, you should see marks on the old gasket and the head or block where the gasses were blowing through. If you don't find that kind of failure, really investigate the head and block for cracks.

Another common problem is corrosion of the aluminum head or block that eats into the "fire ring" seal area. That will require replacement or rework by a machine shop.

 

You seem to be forgetting about the thin Viton rubber layer of the MLS gasket. It's that rubber that fails over time to "blow" a head gasket.

 

Thin layer of it too. But as long as both surfaces are true it shouldn't go again.

 

I use a ruler as a straight edge all the time, but it's a Mitutoyo

 

The one I just got is Starrett, ground to within .0001"

Not sure if that going to be accurate enough.

 

There is no "seem" to it. You measure flatness with a straighte-edge and feeler gauges by measuring in multiple directions and if you can push a .004" or greater feelr gauge between the head and straight-edge it needs to be milled flat. A properly post milled head should be .002" or less. Your engine's cylinder head most likely warped at a location(s) between the coolant jacket and cylinder.
Read: AGCO Automotive Repair Service - Baton Rouge, LA - Detailed Auto Topics - Symptoms of a Blown Head Gasket

Checking for flatness:

 

Oh you fancy!

 

The key not mentioned here and shown so wrong in the video is you use a precision straight edge not a ruler. A ruler can have variances of .01" no problem which will give false readings all day long.



It's all that is available to me locally. Mitutoyo would have to be ordered online. But I'm pretty sure Mitutoyo has the same specs.

 

Which model/length did you get, TomCat? I've got some head work with a straight edge I've got to do in the coming months. I could use your feedback. Thx.

 

Sorry @deschlong, I actually posted it in GDD in the latest purchase thread, but that thing grows sooo fast. I was a little off the precision but it's still plenty accurate enough at 0.0002" per foot.

I bought the 24" as I figured two feet should be long enough to go diagonally across the blocks or heads I'm testing. Might get a longer one down the road but think this should do for now.

 

De-******* is going to do head work?..lol

 

de-******* likes to get head work done, it's true

 

Likes to get head