Should I Replace One Cylinder

Gator · 11-16-2007, 06:50 AM

I've had my 86 Carrera for about two months now. My first Porsche. While changing my plugs yesterday I found the # 5 cylinder is burning oil. The rest of the plugs are a light tan. There are signs of a little smoke upon startup but no smoke while driving. It could be valve guides. My question is: Is there any reason I can't remove that one cylinder Head and check and replace the guides (if needed) and check the rings and cylinder without doing anything to all the cylinders? It looks like I could remove the parts without any difficulty and the engine runs great so I really don't want to overhaul the whole thing if its not necessary. Well, I know I can do this but is it a good idea? The car has 130,000 miles on it and runs strong.

silverc4s · silverc4s's Garage

I suggest a compression & leakdown test on all cylinders before you take anything apart. When was the last tune-up / valve adjust done? Was there a PPI done at the time of your purchase?

Fixing just one cylinder is not as easy (or rewarding) as you might think beforehand, IMO, on ANY engine, and probably less a good plan on our flat sixes...

Anyway, good luck with the problem, keep us up to date on your work.

ZOA NOM · ZOA NOM's Garage

It can be done without much trouble, but it doesn't make sense to tear it down that far and not address the whole thing. It looks like a classic "while you're in there" to me. To get to the cylinder, you'll have to remove the cam tower, the chain housing, and one of the other cylinders on that side. This will all require removal of the motor, and an engine stand. By the time you get to that point, it just doesn't make sense to limit the work to just one cylinder.

Gator · 11-16-2007, 07:52 AM

Quote:

Originally Posted by silverc4s

When was the last tune-up / valve adjust done? Was there a PPI done at the time of your purchase?
Anyway, good luck with the problem, keep us up to date on your work.

I bought the car with no PPI. I haven't had time to adjust the valves yet but its on the list. I have already been into the car quite a bit and it looks great except for the # 5 cylinder issue. For an E Bay $10,500 car I think I still have a good deal! I think I'm going to just watch it for a while and enjoy it some more before a teardown. The plugs in the car had a .045 gap from wear so the leak isn't bad enough to foul the plug.

yelcab1 · 11-16-2007, 09:58 AM

Certainly a good deal.

Now you get to deal with the $1000 valve job if you do it yourself. $3K to $4K if you let a mechanic at it. No sense in just changing the one valve seal if you tear it down that far, especially if you are doing it yourself and saving all that money.

Zef · Zef's Garage

Pulling just one cylinder is OK if there is just that one that is sick...regularly done it on Lycoming\Cont aircraft engine...If all others cyl. give good results on leak down check...why to remove and OH them...!...Ho...and welcome aboard Gator.

Eagledriver · 11-16-2007, 08:59 PM

It's unlikely that a single cylinder would wear out it's valve guides. More likely a broken ring. You can drive it for years that way and when that cylinder starts to misfire you can rebuild the engine.

-Andy

Gator · 11-17-2007, 05:51 PM

Thanks for all the ideas. I'm going to drive it for a while and have fun.

MKEDF · MKEDF's Garage

I also bought a porsche 7k..

Great Deal, i even drove it from Reno to San Diego...

As i got to LA Smoke!!!

But it was running so strong....all the way...

As we teared appart, we found two broken pistons (Happy Timming, or Low octane Fuel), then the valve guides were worn out, and a spring from the heads was broken, ONE valve was worn out (strange, but real).....

So be aware when one thing happens, usually many others related come out, if you suspect something is wrong, there are many other related that you should also look..