RTV Crankcase Bolts - Terrible or not?

kclem19 · 01-30-2016, 06:34 PM

All,

I got some feedback that RTV on those orings is not good because you can actually have bad oil leaks because of it and potentially getting foreign material in the crank mains. If this is so bad, how did it make it in Wayne's book? Is it really that bad or not. I was told I should take off my top end to remove the RTV and reinstall orings slightly lubricated. Has anyone had failures recently after rebuilds caused by using RTV here?

Thanks,
Kelly

Alan L · Alan L's Garage

I used as per Waynes book on my SC about 7 yrs ago. Not a drop so far.
Alan

VFR750 · 01-31-2016, 04:00 AM

Is the engine built and running?

Flat6pac · 01-31-2016, 05:34 AM

I've been building for 35 years and have taken apart destroyed engines that were assembled with RTV including an early S engine.
Bruce

Iciclehead · 01-31-2016, 06:10 AM

Quote:

Originally Posted by Flat6pac

I've been building for 35 years and have taken apart destroyed engines that were assembled with RTV including an early S engine.
Bruce

Was the root cause of the destruction errant bits of RTV plugging up oil galleries and such?

As much as I trust Wayne, I must admit I don't like the practice....

Dennis

Alan L · Alan L's Garage

Quote:

Originally Posted by VFR750

Is the engine built and running?

If you are referring to my SC - yes - has been for 7 yrs. Runs like a swiss watch. Off on a 1000 mile trip tomorrow. Has never let me down in 10 yrs .
Regards
Alan

Steve@Rennsport · 01-31-2016, 12:24 PM

JMHO,....

Without any exceptions, RTV should never be anywhere near a 911 engine during assembly.

I've seen FAR too many ruined engines over the past 40+ years from the use of that stuff. Leave it for the domestic engines.

Lyle O · Lyle O's Garage

Quote:

Originally Posted by Steve@Rennsport

JMHO,....

Without any exceptions, RTV should never be anywhere near a 911 engine during assembly.

I've seen FAR too many ruined engines over the past 40+ years from the use of that stuff. Leave it for the domestic engines.

Couldn't agree more with this, from a materials science perspective. While some RTV silicones can withstand the temperature rigors of an engine application, those tend to be pretty expensive (they use a platinum cure system). But, more importantly, RTV is not compatible, as a rule, with hydrocarbon based fluids (oils, gasoline, etc.) unless it has been modified with fluorine (flourosilicone). I really don't know of any room temperature cure system that includes this modification. I sure wouldn't want to risk it. But I'm a polymer junkie, so maybe I over-think this stuff. Good luck.
Lyle.

kclem19 · 01-31-2016, 07:33 PM

I really didn't want to do to take it back down but I guess it's a good time before I install cams and time the engine.

Steam Driver · Steam Driver's Garage

Baaad idea! RTV should never be used on an "O" ring, be it Porsche or your plumbing system. By design "O" rings need to be able to move, not be immobilized, which is what the RTV would do. The theory is that as pressure is applied to the ring, it deforms and seals even tighter. RTV will prevent that. Bottom line is no RTV on any "O" ring, regardless of application be it Porsche or your commode! Lubricants like Dow-Corning 111 or similar only.

Tom '74 911 · 01:58 PM

Quote:

Originally Posted by Steve@Rennsport

JMHO,....

Without any exceptions, RTV should never be anywhere near a 911 engine during assembly.

I've seen FAR too many ruined engines over the past 40+ years from the use of that stuff. Leave it for the domestic engines.

I realize this is a bit more than thru-bolt o-rings, but to Steve's point, here are photos of my (previously rebuilt by an "expert") engine after disassembly. One photo I didn't take was the literal handful of RTV bits I removed first thing when I split the case... Steve (or more likely his elves) had the pleasure of scraping all that cr@p off the mating surfaces & everywhere else it spread when I had Steve/Rothsport rebuild the recently rebuilt engine for me. : ) : )

KTL · 02-01-2016, 01:53 PM

Wow Tom's pictures are bad............ If you ever get a chance to see how small the holes are in the cam housing spray bar, you'll agree that RTV is bad news for these engines. OK, I can't resist. They're basically pinholes

Unfortunately the thru-bolt o-rings act like more of a packer than an actual o-ring. Regardless, the goal is to get them installed without being excessively mangled, which would cause a leak. I believe the recommendation of RTV in the rebuild book was to counteract the mangled o-ring occurrence.

There was a "friendly" debate about this and if you can wade thru some of the argument, there was some pretty good discussion

Your opinion wanted. Green bolt through viton o-rings with rtv

Case Through O-Ring trouble??