Crack between intake and exhaust valve

Hi, I'm repairing the top side of a 1999 Chevy Venture and have discovered a tiny crack between the intake and exhaust valves of the #2 cylinder.

Now I did get a OBDII code saying there was a misfire on this cylinder prior to tearing it down, but I also was losing some coolant for the past year or more and just before I stopped running it, it kept overheating. I figured it was the lower intake manifold gasket again.

My question is, with the mileage at 183K, would it be worthwhile to replace the head or would it be OK to keep running it? If I can get a couple of years out of it, I'm happy.

I also should tell you that the head bolt on that particular corner of the head was quite loose, it didn't have the snap that the other bolts had when I went to remove it. And the cylinder head gasket on this #2 cylinder wasn't quite as round as the others, it had a slight bend to one side, as if pushed over to the edge.

What would you do given the age and mileage? I think I can get used head for around $100, but I'm already into it for nearly $400 because I went ahead and replaced a lot of the problem area parts, rear plugs, wires, rear O2 sensor, etc.

And by the way, there was a lot of the white sludge in the lower intake and valve covers and the gasket was broken between the #1 and #3 cylinders near the top.

Thanks for you help, Toni.

I would fill the crack in with jb-weld and smooth it down and make sure it's not going to stick to any of the valves and then let it set.

I would fill the crack in with jb-weld and smooth it down and make sure it's not going to stick to any of the valves and then let it set.

There are so many ways that this won't work. Not being a jerk, but just don't do that.

First of all, JBWeld is an epoxy putty impregnated with steel. Its plastic with some metal floating in it. Within the first few seconds of firing the engine, it will melt and come off making a horrible mess. Those flame fronts in a chamber can reach 1800-2000 degrees F. JBWeld is also not going to stop the crack. You're talking about a fracture in a casting. It will continue to grow. Stuffing it full of JBW to stop a crack in iron is like filling a crack in the sidewalk with silicone and expecting it to not continue cracking.

Plus that says nothing about the potential for messing up the valve seats.

Toni... A cracked head is a done head, especially when its between the valves. It won't last 2 years, especially if you have a coolant leak and a misfire. My guess is that the misfire is caused by the crack exerting pressure on the valve seats and not sealing them. Keep in mind that valve jobs use tolerances as low as .00012". It doesn't take much to get a valve to not seal on the seat. It might last another month, so save yourself the headache of doing all the labor twice and just buy a rebuilt head for it.

I stand corrected, by Barney but oh well, I've been wrong before, I didn't say that was the right thing to do or that it would even work, I just said that is what I would do, and I would also probably find out after doing so that it wouldn't work. Sorry for the bad advice.

Hey ctwrihgt, don't beat yourself up over your comment. I've been wrong a few times myself, like when I bought this P.O.S. I really wasn't considering doing that anyway. I think JB Weld has its uses, but inside of an engine really isn't one of them.

What your saying curtis73 makes sense. That would explain why the skipping that the motor was doing would ease up after it warmed up some, probably closes the gap somewhat. I guess the coolant leak wasn't necessarily related, it just happened at the same time.

I'll just have to go on the hunt for another head. I called around a bit this morning, but being a Saturday, not all the area yards are open. I do have a guy I've used before and he is pretty reliable, I'll try him on Monday. I really don't relish the idea of doing all this work again. It isn't necessarily a difficult job, its just tedious removing all of the pieces in order to get to the parts you want to repair.

This will give some time to fish the end of the dipstick tube out of the oil pan, which conveniently broke off when I attempted to remove it from the block. I tried my darndest to get it out from the top, but alas I ended up driving it down into the pan. I guess in the worst case, I'll have to remove the oil pan. I think I'll remove the oil sensor from the bottom of the pan next and see what that will net me. I've been fishing from the drain plug hole and so far have come up empty handed.

By the way, the heads are made of aluminum, not cast iron. The engine block itself is made of iron though. I think that's possibly the reason these engines fail, due to differences in expansion and contraction of the metals involved.

All the best, Toni.