leak down numbers - ????????
 

I bought my 85 3.2 a couple of months ago. I got it for a good price but the paperwork showed a leak down test done 2 years b/4 with 80% leakage in the # 5 cylinder. The other 5 cylinders were 3%.
People in the know told me to drive it and burn off the carbon, should go away as the car has an actual 47,000 miles on it. The 22 year previous owner never drove the car hard and had only put 200 miles on it in the last 2 years since he was afraid of hurting it.
So this week I took it to an independent shop that has a great reputation in the area to have another leak down done after driving it hard for 1500 miles since I bought it.
The 18 year experienced Porsche mechanic took it for a test ride and felt confident there was nothing wrong with the engine. Said it runs like a 3.2 should. So I was happy and he said he would call me with the results today.
Well guess what - 80% still, coming out the exhaust, just like the previous shop noted. Valve job needed and who knows what else. The mechanic is baffled. Can't wait to see what he finds out.
Anybody else had anything like this happen to their car or do any of the more experienced guys have any idea what is going on? The suspense is killing me. Thanks in advance.

IMHO you might feel it, but the mechanic should definately notice that leak. Both in lack of power and how the starter sounds!

I had the same leakdown numbers on my 964, and it turned out to be an exhaust valve guide that were REALLY bad. The valve could easily have broken, with catastrophic result to the engine.

I could feel the lack of power and hear on the starter that one cylinder was way off. But on the other hand the car was still very fast, since it is a light and powerful car. Just imagine how fast the car will feel when you get this sorted!

A top en rebuild isnt the end of the world moneywise. A true 47k car is now very valuable, and my guess is that the top end rebuild will add about the same value to the car as the cost of doing it. But shop around, and make sure to get reviews on the shop you choose.

Most likely a 47k car won't need any further work, so if a mechanic suggest that I would ask for a second opinion.


Regards,

Johan

Not sure I'd concede too quickly to a top end rebuild on a 47k mile motor. Based on what you've described, it could just be a piece of carbon lodged under the #5 exhaust valve seat, or an improperly adjusted valve. Ask the tech if he can check the valve adjustment first, and then look into the chamber with a borescope to confirm the condition of the valve and seat before going further.

if the valves sound good, IE, no clicking or tapping, i would just drive it. if it bothers you, just do #5.

Could be something as minor as a piece of carbon in the valve opening as a previous poster stated or something as serious as a burnt valve getting ready to break off and trash a cylinder. I would not just ignore the problem. Although at just 47K miles it would be highly unusual to have a burnt valve, it is not impossible. On the other hand, 1500 miles should have taken care of any carbon problems. First thing I would do would be to check the valve adjustment on that cylinder and hope that it is set too close and keeping the valve from closing all of the way. If the valves are properly adjusted I would try and scope the cylinder and try to get a look at the valves and cylinder walls.

Pull the exhaust and use a borescope to inspect the valve and seat on #5. You should easily be able to see a burned valve. This will also show you if you have excessive carbon buildup which can be cleaned out. Excessive carbon could indicated a valve guide problem.

This is much less invasive than a top end.

Hi,

I've seen poor leakdowns from carbon stuck on a valve seat but there is a possible solution that may work for you.

This is an old-time procedure dating back 45+ years that's still valid and its called "staking the valves". The way this is done is by holding a piece of wood over the tip of the rocker arm (to prevent damage) and striking it sharply with a hammer. If there is any loose carbon stuck on the valve or valve seat, this oftentimes dislodges it so it can fall off.

Sometimes I knock it a few times to be sure, then repeat the leakdown test to see any improvements.

Can't hurt anything to try this as you've nothing to lose and everything to gain. :) :)

If this doesn't change the test results, you may have a bent or burned valve and that should be addressed ASAP.

I suppose I've really dated myself. :)

Thanks for all the ideas guys. I have decided to go ahead and do a complete valve job, guides and all. As well as front and rear main seals and check the clutch. Anything else while I am in there?

I think that's the most prudent thing to do considering the history of these engines.

Good decision.

Steve - I am glad you agree. It might be one of the first "prudent" things I have ever done... :)

So my mechanic pulled the motor/tranny yesterday and the #5 head today.
All but # 5 cylinder were 3% leak down, while # 5 was 75%. He said it looks like a new motor apart from this valve seat and guide.
This is a 47,000 mile car that other than this one little valve guide and now valve seat runs and looks like a new car. I guess it should with only 47K on it!

So the valve stem was flopping around in the guide and did a little damage to the seat so we will probably have Ollie do a complete valve job, replacing all the exhaust guides and this one seat. Then back in Boulder my mechanic will replace f+r main seals, new clutch disc, other seals and gaskets prone to trouble - a cat bypass and maybe 964 cams.
Then all is well in Porscheland again for 150,000 trouble free miles ...

Any thing else I am forgetting?

Wow, it sounds like you dodged a very expensive bullet. A broken valve could have destroyed the engine.

However it is strange that it was that worn, considering the milage. It sounds like a bad guide or bad valve.

To me your list sounds good, but I am no 3.2 expert. Or any kind of expert.... :-)


Regards,

Johan

I had burnt valves on the 88 when I bought it. One very bad. Did the valve job and replaced the guides. All is well. While you're in there, replace the dilivar exhaust studs with steel. By the way, I got the car for a lower price because of the possible engine problems. Still ran pretty good but a friend who drove it said it was not up to 3.2 standards. You don't want a valve to break. Did that on an old VW bug decades ago. Not pretty.