993 engine 'through-bolts' - comments everyone please

orangecurry · 10 Nov 2011

http://www.911uk.com/viewtopic.php?p=696696

Ballcock - did your ex-Indie in the North of england ever mention this?

Bernie - in the midst of your rebuild - what say you?

Geolab?

Jackal?

Zuff - you probably trawl Rennlist more than anyone?

guards red · 10 Nov 2011

Dont have the expertise of any of the mentioned but the through bolts are the long bolts and nuts that hold the case halves together. They have a rubber seal at each end and some run though the oil galleries so can leak.

Unfortunately they are only half exposed, the other half sits in a recess below the barrels and therefore they cannot be removed without major disassembly.

One can try different oil, something slightly heavier which should help. These can leak when one changes the type of oil previously used, say from a non-synthetic to a synthetic leading to gunk being removed from around them leading to leaks. Especially if the oil has cleaning agents.

Hope the above helps.
GR

ballcock · 10 Nov 2011

I've not heard of thru bolts leaking on 993's ... Never heard any indie speak of this either
:dont know:

Paul Farrar · 10 Nov 2011

I understand leaking 'through bolts' were more common on 964s, although apparently the seals were changed late in the run which largely cured this. However, it is not unheard of for early 993s to weep a bit.

On my original 993, this was first picked up during routine servicing at around the 45,000 mile mark. The 'leak' was limited to one bolt though. When I sold the car at 122,000 miles, the 'leak' had not worsened at all.

People get paranoid about oil leaks! It all depends where they are and how they deteriorate (or not).

Single 'through bolt' leaks, provided they are minimal, should not be a problem. Incidentally, I always used good brand 10W/40 semi-synthetic oil, so cannot judge how my 75,000 mile+ through bolt leak would have developed/performed with Mobil 1 or similar....!

ballcock · 10 Nov 2011

I've just done a quick search on RL and found 2 threads , none newer than 2006 ..
Nothing more sinister than Paul's post above..
Similarly , one poster put 40k miles on a 993 that had supposedly a thru bolt leak, including track days with no consequences.

Apparently these leaks are difficult to detect as other much more minor leaks (timing chain cover leaks?) can run down the outside of the cylinder bases making it look like a bolt leaking.

A search of the 964 forum gives a good few pages of thru bolt leak topics.

From memory , the '89-90 964 engines didn't use gaskets between the cylinders and the block , so causing most of the problems.

stewart rix · 10 Nov 2011

I was advised that the crankcase gasket was starting to leak (the tiniest of drips was starting to form on an otherwise dry motor) on my previous C4 when it was taken in for a PPI by a prospective buyer. The indie advised the only way to cure it was a complete (£3000) engine strip down to replace the gasket. The perspective buyer demanded that much off the price (as though I had a duty to do it because he'd paid for the PPI! :floor: ), I refused, he walked. The indie said he would expect to see a lot more in the same situation as the gaskets, now at least 15 years old, give up the ghost.

Zuffenhausen :O) · 10 Nov 2011

As Barney says not much on Rennlist relating to this issue, but there is a good piccy here showing the offending article.....the O rings in the crank case. In all honesty I cant remember ever having heard any real issues relating to this, its been more gearbox, valve gear, steering rack etc, Im certainly not concerned about a potential oil weep, it stops the road salt from taking hold!

orangecurry · 10 Nov 2011

Conclusion: so it's not something to even consider having done, unless the oil is pouring out. Do take note that Rennlisters are manic about such things.

ps guards red - how could I have missed you off of the list?

:wack: :wack:

Will you ever forgive me?

rottenbend · 10 Nov 2011

^^^ Agreed

I have a small oil weep at the moment (in addition to lower rocker covers

) I thought it was an oil return tube seal but it could be this. If it is there's no way I'd have an engine rebuild done. Engines weep oil, it's a fact of life - deal with it (despite the OCD :grin: )

geolab · 10 Nov 2011

Just for info, the O-ring at the end of the through bolts is to prevent oil from going out of the case IF EVER there is internal oil seepage. But the through bolts are NOT in oil, and as you see in the picture, the passage where they pass through is sealed with the same sealant, that seals the case.
So no oil and pressure behind these seals.
regards

clarkycat · 10 Nov 2011

Paul Farrar said:
On my original 993, this was first picked up during routine servicing at around the 45,000 mile mark. The 'leak' was limited to one bolt though. When I sold the car at 122,000 miles, the 'leak' had not worsened at all.

And i own that car now, at service i was told of small leak that was 'not worth worrying about'. Did not even know what it was until Paul said at Windsor.

People get paranoid about oil leaks!

Ha!

They should try owning a real leaker! My Red esprit had various tubs on the garage floor to catch oil, gearbox oil, coolant etc from the various rads and coolers underneath. never lost any sleep over it, just had to park bang on.

Always figured if it stopped leaking: It needed topping up!

Zuffenhausen :O) · 10 Nov 2011

Heres a bit more info on the subject, as usual GR's hit the nail on the head ................:thumb: scroll down to the lower link on Mike J's post (Sealing the case (or tomb)) on Pcar with his rebuilt 993 engine, outlines the potential for leaks from the through bolts and some tips on how to install the O rings without cutting them.

http://forums.rennlist.com/rennforums/993-forum/565915-through-bolt-o-rings-964-vs-993-a.html

guards red · 10 Nov 2011

geolab said:
Just for info, the O-ring at the end of the through bolts is to prevent oil from going out of the case IF EVER there is internal oil seepage. But the through bolts are NOT in oil, and as you see in the picture, the passage where they pass through is sealed with the same sealant, that seals the case.
So no oil and pressure behind these seals.
regards

Hi Geolab,

Thanks for the picture. My understanding, and again just a layman's view, is that the crankshaft is oiled through the main bearings, the crank then oils the conrod big ends. See below:

The oil therefore runs through the crankcase around the bolts I believe. Not expert so I could be wrong.

Hi OC, no need to apologise. People often tell me I talk s**t so I wouldn't pay me no never mind either!

Regards
GR

ballcock · 10 Nov 2011

Sorry to state the obvious but ...

Damn it's great to be able to rub virtual shoulders here with guys like Geo and GR ..
I'm learning loads , thanks guys.

orangecurry · 10 Nov 2011

It's like being able to rely on the best engineering team in the wuuuurld, added to which you know they are not trying to make money out of you :thumb:

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