2bridges

This is actually a very typical looking head gasket failure...... Is often very small

I must disagree with alot of what I read about serious issue with carbon..... If this is a very high mileage engine that is not uncommon to have build up. Granted 1 and 4 are worse and would be wise to check out those injectors, but this truly is not that bad as some are indicating is a sign of serious issue. Simply not true

Mongo

who says worn rings are a serious issue? Your rings are leaking on your motor all the time. You are just letting oil so minute get through, that it cannot be measurable. When engines get older they tend to eat more oil, hence carbon buildup also.

2bridges

UHHHH........ not trying to ruffle any feathers here, but to be blunt
The amount of carbon build up is NOT EXECESIVE.
I believe it is misleading to say a re-ring is needed based soley on that carbon.

Mongo

it's also based on a compression test too.

2bridges

just keeping you honest.

I would put 90% more weight on the results of a compression and leakdown test than those moderate carbon pics.

Porsche-O-Phile

It's the #2 cylinder and yep - I saw that right away. Toss that one away & replace. While you're in there, clean up those carbon deposits and look at (among other things) O2 sensor & injectors.

2bridges

GOOD SHOW JEFF - #2 not#3

Okay Stigmiester... I re-read orig post... I don't see any compression info ???

PeteL

No, there was no compression test before teardown. I had all of the symptoms of head gasket. I was slowly (very slowly) losing coolant. The car ran like crap when cold, and I had one plug that was significantly cleaner than the others.
I did not notice the break in the gasket, and will look at it again when I get home.
The injectors were cleaned and flow-matched a few years ago, I have a spare set, so I will do that again.
Game Plan: Reassemble the car this weekend, (after thoroughly cleaning up the pistons etc. and see what happens.

500

Very often rings are called out as a possible culprit for excessive oil consumption but on these engines, there are other, more common causes.

Two that I would also consider are the valve guides (already mentioned) and the air/oil seperator o-rings. If these fail and allow air to flow throught the air/oil seperator, the flow will draw off a lot of oil mist from the crankcase and will lead to oil burning (the air/oil unit is connect to the intake tract as well). Try looking inside the throttle body, lots of oily residue here is an indicator of that particular problem. Easy and cheap to fix right now, and pretty common too.

Jay W

I see you are going to put the head back on this weekend. Are you planning on having the head re-surfaced before you put the engine back together? When you have that done you may as well have the valve guides checked as well. I am currently in the process of replacing the head on my 88 n/a and it is an awful lot of work (and a $137 head gasket set) to put back together without checking out the components in it.

PeteL

Where exactly are the air/oil separator o-rings?

ibkevin

Sooo, get the head rebuilt, get the injectors rebuilt, install a quality OE headgasket (no troublesome boost to get in your way), fix any front end crap that has been on the do do list, and be on the road for Spring!

testarossa_td

https://rennlist.com/forums/showthre...ight=aos+rings

PeteL

Great! good link. I see only one bolt that holds that assembly in place, is that it besides the hoses etc?

500

Here is the PET screen shot:

As is normal for PET, they only show repeated nuts and bolts one time on the drawing. I think it is three bolts.



The O-rings are the two small ones that plug into the block (#16 and #44 and a larger one on the filler neck (#18). There is also another one between the upper portion of the a/o seperator body and the lower portion. However, this is not called out seperately in PET. Replacing the whole a/o seperator is one (expensive) option, another is finding an equivalent O-ring at an auto parts store (which some people have done, or, just leave it in the hope that it is still good. In my case, the a/o unit was broken so I have to buy the unit anyway.

Incidently, TechnoDuck (Jon) who posted the thread that testarossa linked to, found that in his case replacing the three seals completely solved his oil burning issue (no other work was done). Does not mean that it is the same issue for you, but it is pretty common.

Part numbers (for 1987):

#16: 999 701 661 40
#18: 999 701 653 40
#44: 999 701 613 40