fperra

Well, if you decide to pull the head, I've got a full set of valves and springs from an '02 engine with only about 8000 miles on them. If you want them, stop by and pick them up. No charge.

SpitfireS

Ek9 Posted on Jul 30 2006, 05:35 AM
That seems like an easy thing to try yourself to determine if its a valve or a piston / piston ring / cylinder wall problem.

RED MX5

OK, so whatever is going on with #4 probably isn't realted to the work you did. Have you done a wet leakdown test? Did you do wet and dry compression tests? Knowing those test results might give us a better idea of what's going on.

I wish Billman would chime in.

RED MX5

Mike, earlier this year we had two cars in the shop that had intake valves that were not sealing. In both cases it was due to a shoddy valve job. Anyway, our youngest mechanic isolated the leak to the intake valves in a way that I'd never seen before. You might want to try this.

Take the fitting you used to pressurize the cylinders when you changed the retainers, and pressurize #4. If the intake valve is leaking you will hear it hissing through the intake. I suppose if it were an exhaust valve you might be able to hear the hissing through the exhaust, but I don't know that for a fact. I'd also bet that if the leak is from rings then you'll hear the hissing through the oil filler opening when you remove the cap.

Apply pressure and listen.

Ek9

I think he's done that already because he's doing a leakdown test.

I'd still like to know if there are any bubbles in the radiator when he's pressurizing #4.

mikegarrison

I hear noise and feel some air movement in the inlet when I have #4 pressurized. That's why I suspected the inlet valves from the start. But not enough to be positive that's the issue.

I'm leaning towards buttoning up the engine and seeing if it will run. I'm not sure that I have anything to lose. I don't want to screw around with taking the head off. If it comes to that, I think I'll just get it to a shop and pay somebody to do it.

I didn't think to look for bubbles in the coolant. Guess I'll try that too.

mikegarrison

I'm pretty sure the problem is in the inlet valves. I pulled the inlet duct off of the manifold and I can hear and feel air blowing past the throttle valve when I am pumping air into #4. With the other cylinders, that isn't happening.

There is no sign that air is going anywhere else.

xviper

I'm sure I'm really reaching here, but make sure that all valves on #4 are indeed "closed" - all cam lobes are in the correct position before pumping that cylinder up.

CoralDoc

The cams and rocker arms are off the car (see post #4), so there is no way that the cam lobe can affect the valve seating, unless the lobe is REALLY long .

xviper

Forgot. It's been a while.