Bad leak down results

[Solamar]

Just purchased a 3.2l complete engine with zero history.

I am expecting a few surprises, but the leak down numbers arent good and I'll need help with the diagnosis and course of action.

Snap on Leakdown tester, tested in firing order order and only pulled plugs at TDC prior to each cylinder test.


All the plugs looked great, uniform color, no differences between cylinders -


Results -

#1 45%
#2 6%
#3 6%
#4 22%
#5 8%
#6 6%

Cylinders 2,3,5,6 I can hear a small bit of air escaping through the breather. Nothing at exhaust or intake.

Cylinders 1 & 4 no air escaping from exhaust or intake, small bit at breather (same as others) but can hear, feel and see air escaping at the head to cylinder mate.

The top of both 1 & 4 cylinders look the same (oily) and oil bubbles at the joint during the leakdown


Broken head studs, right? But there not broken. I put a wrench on all of them and applied a small bit of force, I did not attempt to re-torque.

What should I do? A full rebuild is not in the cards right now. If I have to, I'll pull the heads and cyl's, install new studs and reassemble.

Any ideas?

Can I re-torque the head studs?

[proporsche]

where was the leak? to the engine case or to the exhaust?
Ivan

[Solamar]

Originally Posted by proporsche

where was the leak? to the engine case or to the exhaust?
Ivan

Neither. From the combustion chamber OUT via the head to cylinder mate. Would be considered a head gasket leak if there were a head gasket...

[john walker's workshop]

Might as well just go through it, from the looks of all that dirt and goo. Probably a good rebuildable core though.

[BK911]

Might be able to lap the head to the cylinder.

[proporsche]

well...do it again and pay attention ....it has to go somewhere specific.....i do not see on the engine any problem with cylinder heads ...it is either piston,piston rings ,valve guides ,valves them selves..
As John said really, take your time and do the whole thing...at least he the top, of course..
Ivan

[Rawknees'Turbo]

Was the leakage test done cold? If so, you would have much better results if done hot.

The air you hear from the breather is piston ring blowby - might simply fix itself if you heat cycle the engine a few times, but another thing you can do to free-up the rings, and this really works (common to do with aircraft engines that have sat idle for years) is use a syringe with vinyl hose attached to the tip (just the! ) and liberally apply Marvel Mystery oil with it, through the spark plug holes (use hose to direct the MMO to the topside of the cylinders/pistons so that it runs downward and coats the rings as you stroke the pistons through their range of motion.

Not sure about re-torquing the current studs - those are Dilivar, correct? If so, a good chance they will break, but then again, something has to be done about that leakage, so you are probably looking at replacing the studs along the way anyway.

[Solamar]

Originally Posted by proporsche

well...do it again and pay attention ....it has to go somewhere specific.....i do not see on the engine any problem with cylinder heads ...it is either piston,piston rings ,valve guides ,valves them selves..
As John said really, take your time and do the whole thing...at least he the top, of course..
Ivan

Hi Ivan,

The air pressure from the combustion chamber is leaking out between the head and the cylinder. See area circled in red below. I can hear, feel and see the air escaping.

[Solamar]

Originally Posted by john walker's workshop

Might as well just go through it, from the looks of all that dirt and goo. Probably a good rebuildable core though.

Thanks John, appreciate your input.

Short of a full rebuild, whats the budget friendlier solution? I assume the head mating surface has been compromised, so head job required. What about the mating surface on the jugs, can that be damaged? Repairable?

[Solamar]

Originally Posted by Rawknees'Turbo

Was the leakage test done cold? If so, you would have much better results if done hot.

The air you hear from the breather is piston ring blowby - might simply fix itself if you heat cycle the engine a few times, but another thing you can do to free-up the rings, and this really works (common to do with aircraft engines that have sat idle for years) is use a syringe with vinyl hose attached to the tip (just the! ) and liberally apply Marvel Mystery oil with it, through the spark plug holes (use hose to direct the MMO to the topside of the cylinders/pistons so that it runs downward and coats the rings as you stroke the pistons through their range of motion.

Not sure about re-torquing the current studs - those are Dilivar, correct? If so, a good chance they will break, but then again, something has to be done about that leakage, so you are probably looking at replacing the studs along the way anyway.

Yes, cold and the engine been sitting for a year or so. I'd expect and be happy with the 6-8% leakage. Like you said an Italian tune-up would probably cure that.

Leaking at the head, thats a whole nother animal...

[pmax]

Are those cylinders even alive ?

[Walt Fricke]

I'd retorque those two heads. Nothing really to lose here. Whether you get any movement or not, and whether or not redoing the leakdown on them mproved, I'd then go run the engine and leak those two again and see if expansion from the heat changed anything.

But it looks like you don't have the engine in the car, so heating up the cylinders and heads probably isn't in the cards. So put it on the engine stand, and remove enough (which is quite a lot) to get those two heads off, so you can see what sealing surface damage there is. Both the cylinder tops and the head sealing surface can be machined back to true, and the difference (total removed) made up by putting thicker copper spacer/gaskets under the cylinders.

Of course, while you have the cam carriers off, might be good to check for play of the valves in the guides. And then, . . . . . ..

[proporsche]

Solomar..you can always do this .Have the groove cut and install cylinder heads ring like it was on 911 SC models.This one i did on my last engine 3,2....i just do not know in southern CA who does this job.I had it done here
Caruso - spécialiste Porsches : entretien, préparation, occasions ...

[proporsche]

one more pic from the left side of the same engine...
[IMG][/IMG]

[Nick Triesch]

my 3.2 had a huge leak where the head meets the motor. Only two things you can do. Top end or full rebuild. My shop checked the torque of the studs first thing. All tight. My motor was doomed, Head leak and swallowed the lower intake gasket on cylinder number one.

. I still have a Wife!!!

[gtc]

I had a similar problem on a couple of barrels. There is a limit to how much you can take off the top of the cylinders as well as the head. Most of mine could be saved, but i did have to replace a head and one or two cylinders that had some cracks that were too deep.
Here are some photos of a head and cylinder that were replaced:

Originally Posted by Solamar

Thanks John, appreciate your input.

Short of a full rebuild, whats the budget friendlier solution? I assume the head mating surface has been compromised, so head job required. What about the mating surface on the jugs, can that be damaged? Repairable?

[Walt Fricke]

Some of this is economics. 25 years from now, it may be more economic to weld and machine for cracks like these Graham shows. But for now good used parts are less expensive (and more certain, fewer possible complications, quicker to get assuming even possible).

Graham - my assumption for sealing surface damage was that something small led to super hot combustion gasses escaping, which led fairly quickly to something much deeper, etc. But your photos don't show that kind of damage. What do you think caused this sort of radial cracking? The photos are fascinating in how sort of regular these many cracks are.

[Solamar]

Top end it is.

Pleasantly surprised that everything came apart without drama and all the bearing surfaces look to be in great condition (cam, rocker shafts, wrist pins). Cylinders are Mahle Nikasil and the cross hatching looks like it was done yesterday. Even the cam chain guides showed zero wear.

Heads needed all new guides and two new exhaust valves.

Waiting on some new Supertec head studs and I'll start putting it back together.

[proporsche]

good job and good news...it will fun from now;-)
Ivan