another oil pressure sender leak - won't go away

chancecasey · 09-23-2006, 07:50 PM

OK - I just tried another brand new viton o-ring, cleaned and polished up the base that the o-ring goes on, cleaned up the case where the sender base mounts. I don't know what else I can possibly do! Leaks around the o-ring and is making a mess. I'm afraid to tighten the nuts anymore (I think I have a good 7 foot pounds on them already).

Every thread I've read said just clean it good and use a new o-ring - well I did that, there are no burrs or dents or anything, and it still leaks at high RPMs. I guess I could try cranking down the nuts a little more, but if the o-ring isn't stopping it I don't think cranking down harder will help.

I know it's "wrong" but if I were to use some sealant like threebond 1104 or 1211 - which one should I use? Maybe I should just spend more money on a new base, new o-ring and try again? What would be so "bad" about using 1104 or 1211 as long as I had a good clean surface and let it cure fully before use?

Tyson Schmidt · 09-25-2006, 08:01 PM

I bet it isn't the o-ring.

I had a mag-case motor that looked like it was leaking from there. Only got wet when run at high rpm's. Turned out to be a rear main seal that the flywheel was flinging the oil up through the opening in the top of the bell housing, then running down in the area near the t-stat/pressure sender.

BTW, tightening the bolts tighter won't help, since that won't put any more pressure on the o-ring.

chancecasey · 09-25-2006, 09:59 PM

Well, thanks to wifey, I made sure this was the problem - by removing it, cleaning it all up, putting it back, cranking the motor (with the air cleaner box off) and sticking my fat head in there with a light while she revved it up. Not only was the oil leaking out from under the base, there were air bubbles/spattering coming from under there as well. We'll not discuss having to remove the afm to retrieve the "protective" paper towel I had stuffed into it. Man I almost messed myself - but the towel was intact.

All I can think of - if it really is impossible for this thing to leak if installed correctly, is that maybe I didn't lube the o-ring enough (I noticed it leaked significantly more when I put it on after the cleaning and no lube, vs. some axle grease I put on it the first time around). Or, maybe my pressure relief pistons aren't working correctly - even though I cleaned and wire-brushed the heck out of them on the rebuild.

I'll go get another new o-ring and really make sure I lube the crap out of it with whatever the hot-stuff o-ring lube is these days, and give it the nice, slow, back-door-style insertion it deserves.

shbop · 09-26-2006, 07:17 AM

Dow Corning 111 Hot stuff o-ring lube.

Tyson Schmidt · 09-26-2006, 05:46 PM

Good work on the diagnosis. That's the only way to know for sure.

Sounds like you have the right idea how to fix it, and also sounds like you know what you did wrong.

I've found that o-rings like better lube than just motor oil. The best I've used is Hylomar made by Permatex. The non-aromatic kind that never dries.

The kind that smells like acetone is no good for o-rings, since it dries out quickly, and is therefore a poor lubricator.

88911coupe · 09-27-2006, 07:12 AM

For some reason I can't focus on anything in Chancecasey's posts...my eyes keep wandering.

chancecasey · 09-28-2006, 07:21 PM

OK I'm a big dummy. It was the plug that sits about 2 inches away from the sender. If I had my laptop with PET I'd sound a lot smarter and say whatever it really is. I DID see bubbles from under the sender base previously, but turns out that was not the source of the pool of oil.

What finally tipped me off is that (and this is REALLY hard to see) the "boss" or whatever the plug screws into is slightly raised from the case. When I saw oil surrounding the plug itself, I thought, well, oil generally doesn't go uphill unless there's some kind of capillary effect.

Well, I took the plug out, noticed the alleged crush washer which did not look very crushed, which also did non fit exceptionally well (it was the closest-fitting one in the rebuild kit - but with my luck probably not the right one). With the lack of fit, crush, and ease of untorquing it - I decided to throw on a copper washer I had laying around that fit great, torqued it down about as tight as I could in the confines of that area, and VOILA! No leaks there or the sender base, even as I hit the rev limiter sitting there in garage (I have to be thorough of course).

WOOHOO this is huge. Now i just need to clean everything up. What a freakin' mess. Too bad I can't buy a beer for everyone saying it probably was not the sender. Thanks for all the advice everyone!

DW SD · 09-29-2006, 07:03 AM

Chance,
Congratulations!
Make sure you spray a bunch of degreaser into the transmission. There is a hole at the top of the crankcase. I had spilled some oil when troubleshooting the low oil pressure issue (changed sensors when hot) and a bunch of oil ran out and into the bellhousing of the trans.

Weeks later I thought the trans was leaking, though it has red fluid inside. I never saw any red fluid, which was confusing. After dropping the motor for the latest project, I finally concluded it was residual engine oil that slowly kept leaking out - weeks later!. A good degreasser or brake spray may do the job.

Doug