2.7 head leak
 

I just went to pick up my '75 from the body shop with a shiny new paint job. It went in on 6, but now appears to be running on 5 after sitting for several months (OK, maybe a portrait and not a paint job). I have pulled the wires off one at a time, and have identified the middle cylinder on the right side. The fouled plug confirms this. I have changed plugs, switched wires, and the problem persists.

I pulled the intake pipe with injector, and appear to be getting fuel. I checked compression with a borrowed gauge and it appears to be low, but same as one next to it that works, so suspect the gauge...only reading 35 lbs.

On a whim, we squirted soapy water onto the injector seal to check for leaks. We found that it was bubbling not at the injector, but rather where the intake tube mounts to the head as well as at the valve cover.

I removed the tube, checked the gasket, and have replaced it twice now. After double gaskets and sealant, it is still leaking as well as the valve cover near the area. Ironically, the gasket and surfaces appear fine with no sign of blow out.

So, to recap, the cylinder has spark, fuel, and appears to have low compression. The rings are fine as the oil pressure is strong and no smoke out the back. The engine runs fine at high RPM but lurches at low RPM.

All thoughts welcomed. :(

blowmeup2001 ,

I wouldn't think that there should be enough pressure in the intake or under the valve cover to create soap bubbles - unless you had an intake valve that was not closing. It's the exhaust valves that burn - so why, when sitting, would an intake valve stick? Carbon holding it open? Valve binding in the valve guide? I've heard that compression checks are not that accurate, that you really want to do a leak down test to see if the intake valve is not sealing.

Rex

HMMMMM....oil P and ring sealing,not too much in common,,rings are no indicator of oil P.
try me again,where is it leaking?? Valve cvr?,,or do you mean intake runner??

well I re read your post....don't panic!! warm it up and use a reliable comp. tester so we have some results to work with here and can chase dwn the problem or we will be going in to many directions......and I get confused ezly

Afterburn is right - more info. After I thought about my previous post - it doesn't make any sense. I don't think you can get pressure at the intake runner where it attaches to the head. Possibly you are seeing air escaping from under the engine cover, that is pressurized by the cooling fan. And if an intake valve was stuck open, you would hear that poping though the intake. Something else is going on. Have you pulled the valve covers off to see if everything is still where it should be - broken rocker arm, or broken elephant foot, or striped adjusting screw......?

Rex

Italian tune-up time. Drive it hard for 1000 miles, and then do the tests here:

http://www.pelicanparts.com/techarticles/mult_Engine_Rebuild/mult_engine_rebuild-1.htm

-Wayne

Thank you very much for your input. In response, it is the intake runner where I see the bubbling as well as at the valve cover at its top mating surface. I have given thought to the situation and also have not identified a way to build enough pressure at the intake runner to cause bubbles. The mechanic I was with felt that it was coming from below, so perhaps the cover/blower scenario is correct.

I had someone watch while I turned the engine over with the intake runner off, and the valve was actuating. There is no horrible or unusual detectible noise or popping. It just runs rough at low RPM as it is not running on that cylinder. We did not remove the valve cover.

I suspect a valve guide as there was oil on the plug. I guess a leak down is in order.

One more thing, Wayne, I did drive it about 100 miles on the freeway at 80 mph with no change to the condition. Would this be enough?