Hey all, I've been chasing a misfire over the last week. Changed plugs, wires and ran electrical tests to rule out what I can. I ran a compression test his morning and this is what I got:

Cylinder Compression
1: 185 psi
2: 180 psi
3: 180 psi
4: 180 psi
5: 20 psi
6: 160 psi
7: 20 psi
8: 160 psi

Research is saying a blown head gasket. However, I am not seeing any white smoke. Could this be the case?

My thinking is a stuck valve, but any thought are welcomed. Trying to keep myself from ripping things apart and make a mess before I have to.

Codes: P0307, P1313, P1316

Last oil change: 4k miles ago. Color is dark brown.

D1 1996, 4.0 V8, 175k miles.

 

Some more testing and research:

Apparently a blown head gasket doesn't always fail around the coolant passages. Could have failed between the two cylinders (7 & 5). Hence why I'm not getting any white smoke or frothy oil.

I ran the engine with my coolant expansion cap off to see if any bubbles appear and nothing.

Head Gasket blown at the bridge between cylinder 7 & 5? I'm getting a tone of wet splatter out the back of he exhaust. Seems like condensation, but smells like fuel.

Going to try and do a leak down test tomorrow. Any thoughts are welcome.

 

Well, if its stuck or leaking valves then the cylinder head needs to come off. If its a bad head gasket then the cylinder head needs to come off. Looks like time for diagnosis by disassembly. Good time to check lifters and cam. Agree with using leak down tester before taking the head off.

 

Pull the valve cover and crank if over to see if the rockers are moving correctly. Could be wiped cam lobes. This is what happened on mine but was cylinders 1 and 8.

 

Oh dang, that sounds like a much bigger job. How did you go about fixing that?

 

New cam and lifters. But I really think your issue is probably a head gasket.

 

So I ran a leak down test and cylinder 7 was blowing air straight into cylinder 5. I suspect a blown head gasket between the two cylinders. I've started deconstructing the top end and so far so good.

I did see some oil sitting in the upper intake. Is this normal?




Cam, rods and lifters look pretty good. Any thing look off to you all?




Started taking the exhaust manifold off, and I was shocked to learn that most of the bolts were finger tight. I barely had to use my socket wrench. That seems a bit concerning. Also, these bolts don't seem right for the exhaust manifold, would anyone know?




Overall the process has been smooth. Taking my time. Any pointers please do let me know. I would like to give the engine a nice clean so any recommendations there is appreciated.

 

Normal to have oil there, it comes in from the R valve cover tube, then there are little holes (that can get blocked) near the trumpet bases (four I think) to drain the oil. Make sure you replace that oil separator in the R valve cover.

Inside the engine looks cleaner than should be for a '96 if original miles, so suspect a PO had it apart and maybe did not get the head installed quite right. Might be the root cause of the head gasket failure.

The exh manifold bolts can get loose due to heat cycling if the keepers are missing. That's another reason to think it has been apart before. I am using the spacers from the D2 setup with longer bolts, those don't use the steel keepers that have tabs to bend over the bolt heads. The keepers are a bit of a pain so I really like the D2 spacers, even if they're spendy. Use good quality taps to clean the threads in bolt holes! Good luck with the rebuild!

 

Thank you John!

Definitely a head gasket blown. I got the heads out this evening and just as suspected, a big piece missing between 7 and 5 cylinder. I've got both heads off now and I am prepping them for machine.

Question, as I was pulling the valve cover gasket off, a metal washer from the gasket popped out and fell inside the crankshaft. My heart stopped for a second. My plan is to remove the oil pan and check if the metal gasket fell all the way down, but I am not sure that is how it works. Would you know?

 

Got the heads off and inspecting the damage. Clear head gasket failure, but one thing I noticed was the pistons. Bank 1 has piston 7 and 5 up, and 3 and 1 down. While Bank 2 had piston had 8 and 4 up, and 6 and 2 down. Does that seem odd?