Reuse OE head gasket add some copper spray.

[Dave WM]

Yea I know sounds like a dumb idea, but hear me out.

Just installed a new OE nissan head gasket on to what I think is a good head and block, well prepped, torqued pre fsm etc...

Still getting a exhaust gas leak in the radiator per the blue chem test. I was going to try another head gasket (yea I know the definition of crazy) to see if that stops it. But since the engine is on the test stand and very easy to work on AND I want to try it out, I am going to remove the head, and try some copper spray on the just installed and tested gasket. If nothing else I can add another L to the record book. 

After that L is recorded I will try a different make of HG. Again I have check the block and head for warpage cleaned well before install. I am at a loss as to why this is going on. I will also break out the magnify glass to inspect the head combustion chambers.

[jonathanrussell]

Any chance head is cracked?

Give it a try if you are willing to invest time and energy. I am curious whether cylinders seal correctly given the fire / seal rings will have already been crushed. 

Let us know!

 

[Patcon]

That was my thought too. A crack somewhere else, other than the head gasket surface. Could be head or block...

[Dave WM]

31 minutes ago, Patcon said:

That was my thought too. A crack somewhere else, other than the head gasket surface. Could be head or block...

I had assumed that would be something I could see, I recall looking them both over, perhaps not well enough...

I was thinking of applying some bluing to the surfaces and then running them over some 220 wet/dry on a flat stone (marble or granite) as a better way to see imperfections. I am pretty unsure about a machine shop. Its not something they routinely do, dont want them running .010 off the tops if it only needs .002 etc... Just dont know how to tell if they are competent as I have NO exp with a machine shop.

Edited August 4, 2022 by Dave WM

[Dave WM]

I got nothing to lose on the the spray on the used OE HG, its going to get tossed anyway. May as well have fun while the engine is easy to work on and test (with the test stand).

Here is something new, it had a loud valve tapping sound, this is with the hyd pivots. I used the stethoscope and decided it was on #2. pull the valve cover and sure enough there was play at the pivot even as the lope was starting to make contact with the ramp. The pivots use oil and have a spring as well (weak) I will purge the air out of the pivot, and also verify the well it sits in is getting oil (crank engine ign off, plugs out). My guess is it would have eventually purged the air out, in time if it had been normal driving speeds. Idle testing for gas means low pressure and volume, it never cleared up even with me running it for 30 min screwing with the testing.

My guess is with the engine off there is always going to be at least one valve that is open (the pivot under pressure). Over time the oil inside will leak down. So I presume any time an engine is shut down for an  extended time, this will happen. 

Anyone with a P90a head can confirm?

[Patcon]

I know the BMW's I have worked on have valve tap when they have sat for months. It goes away with a little light driving

[Dave WM]

3 minutes ago, Patcon said:

I know the BMW's I have worked on have valve tap when they have sat for months. It goes away with a little light driving

sounds like the issue, I just was not able to get it to running speed. I wonder if nissan used these hyd pivots on ohter models?