Oil Line to External T-Stat

[911SauCy]

I replaced these babies at the beginning of this year and have been chasing down a warm running condition that mysteriously arose immediately following.

2 things:
-The lines were clean as pictured until a hot day, car was reading around 230-240, and there is now evidence of some oil seepage. I had a ***** of a time with getting one of the originals off and a couple threads were slightly marred...not sure if it's shot
**Is there some type of sealant I could add to these threads to ensure this doesn't keep occurring? Am I looking at getting a new T-Stat housing?

-I have done a LOT of reading about warm running cars, mine is acting similar to many with a bad t-stat. So I ordered the piston and sealing ring...$50 can't hurt, t-stat is orig I will remove and test in water.
**any thoughts on possible piece of metal getting in there and screwing functionality of the piston?

Last, any tricks on getting piston cap off so I don't ruin another expensive part?

[HawgRyder]

Teflon tape can be your friend!
And for the cap....I would be trying to find a pair of channel locks that are big enough to grab the whole unit (with some padding to protect it) to hold the base unit while applying pressure with a good fitting tool to loosen the cap.
A good tool would be like a tube that fits over the cap...with a blade that fits the slot...so that it cannot slip during the operation.
Bob

[pete3799]

No sealant needed on the fitting. It's a compression fitting and relies on the male and female mating surfaces to be clean and free of nicks or burs. The threads do not seal it but should have some Neverseize applied to aid in removal.

[KTL]

Agree with Pete. The threads are not the reason for the leak. The threads just provide the means to grip/clamp the line to the t-stat. They aren't intended to seal. The seal is between the male spherical seat on the oil line and the female spherical seat on the t-stat. Basically a compression fitting.

The t-stat temp regulator shouldn't get obstructed by any debris. The windows in the regulator body are quite big and can pass large things. If you had a large thing blocking the t-stat operation, that's really bad news.....

The t-stat cap tooling is a joke. Whoever at Behr thought a crescent-shaped slot in the cap is a good idea needs a slapjack upside the head. Not to mention the slots are NOT THE SAME SIZE ON BOTH CAPS

I made a tool out of a cold chisels on the grinder that mimics the shape of the crescent slot. I put the t-stat in a vise (protected with plywood "pads") and use a large wrench on the chisel to loosen the caps. Some caps are really stubborn and the chisel begins to dig into the slot and loosen the tool fitment- basically like stripping the head of a flathead screw.

So then I get ugly and bust out the large pipe wrench. Puts some considerable teeth in the caps but so be it. Sometimes the cap just won't come free, even with heat.

I asked a buddy to weld some hex bar stock onto the caps (after removal from t-stat) to make them easier to remove and to be able to tighten them reliably with a wrench. Alternatively, i've seen some people make a crescent "bit" socket with some thick plate steel welded onto a socket. But that still doesn't address the tool wrecking the slot on a stubborn cap. Buddy decided he'd rather play with the new CNC mill and make some new caps altogether.



You can test the t-stat on the car. Get the engine up to operating temperature- even let it idle for a while and raise the temp even more. Feel the oil cooler lines or the cooler. If lines/cooler not hot to the touch then the t-stat is not opening. If hot lines & cooler, the t-stat is certainly open. Sometimes can be stuck open. I had that happen once. Then it eventually decided to close and not open again!

[911SauCy]

I get the fact that it's a pressed fit guys, but I was dilligent in ensuring it was clean on both ends and as tight as I could get the nut when putting it back together. Of all places, there was never a leak in this spot until I changed the lines for leaks elsewhere....AARGG!

Regarding the t-stat itself, the lines get hot etc, but I'm thinking it's functionality just isnt what it needs to be. The car never passed the 200 mark prior to this year, if i drove it on a 60deg day it would take an hour or more to get there. Now take it out, it heats up faster than I ever recall and gets right to the 9 o'clock, or in my case ~200deg mark. If pushed harder it will climb to 230-240, but will not go above 240. Hottest it will peg there.

It's 35y/o and for the $/piece of mind is probably a worthwhile thing even if it doesn't resolve the issue.

[yelcab1]

Originally Posted by KTL

... Buddy decided he'd rather play with the new CNC mill and make some new caps altogether.

I don't have any buddy like that ...

[KTL]

Originally Posted by 911SauCy

as tight as I could get the nut when putting it back together.

You may have overtightened it and distorted the fit between the spheres. Happens on occasion with hose fittings like aluminum Aeroquip, Earl's, XRP, Goodridge, etc. They just need to be a little bit more than snug. Not gorilla tight.

Agree the $50 for the regulator replacement is good preventative maintenance. Nothing lasts forever and these regulators are known to misbehave in the external t-stat.

[JAR0023]

To remove the cap on my external thermostat I used a drag link socket and 18" flex bar. I had just enough room between the thermostat and fender. Proto brand. 1/2" drive 3/4" size. The blade measured just over 7/64" (.115") wide and it fit into the slot in the cap damn near perfect.

I still managed to deform the cap slot a little where the ends of the drag link where. I also had to resort to a little heat and PB Blaster.

Check the Elephant Racing site. I think they have caps with an external hex, but I could be dreaming that up. -J

ETA - Link

Stanley Proto J5444A 1/2-Inch Drive Socket, Drag Link 3/4-Inch - Amazon.com

[911SauCy]

Originally Posted by KTL

You may have overtightened it and distorted the fit between the spheres. Happens on occasion with hose fittings like aluminum Aeroquip, Earl's, XRP, Goodridge, etc. They just need to be a little bit more than snug. Not gorilla tight.

Agree the $50 for the regulator replacement is good preventative maintenance. Nothing lasts forever and these regulators are known to misbehave in the external t-stat.

If there is distortion, I'm assuming it is on the T-Stat housing end as the lines are harder than the aluminum?

[boyt911sc]

Test the auxiliary thermostat in a water bath between 187°F to 195°F. A good working 911 thermostat would be fully expanded as shown in the picture. The thermostat (left most, good) and the right most one is fully inoperative (bad).



Just did this test last week because a fellow member had problem with over heating and his thermostat was the one at the right most (picture). The three (3) thermostat on the left side are my control: Fully expanded (good), half expanded (causing high temp. due to close valve), slightly expanded (over-heating, fully closed valve).

Tony

[911SauCy]

Perfect photo! Thank you.

[safe]

A pipe wrench on the thermostat caps. It will make some marks but who really cares.

[911SauCy]

Originally Posted by safe

A pipe wrench on the thermostat caps. It will make some marks but who really cares.

You mean....patina

[911SauCy]

Ok, now for the stoopid question follow-up.

I just spent 40 minutes with a large wrench (not a pipe wrench yet), then I made a little semi-circular disk to fit in the cap slot and be held with a large vice-grip, added heat to expand the housing on both occasions.

All I got was a broken wrench and bent metal thingy...

Next question, how did you guys hold onto this thing? I think thats half of my issue.

Had it in a bench vice with cardboard tripled up on either end to cushion, seemed to be ok but it was still moving.

Get the wife involved...?

I get annoyed that every time I go to wrench on this car its a serious PIA...least enjoyable car I've ever worked on.

[KTL]

Ditch the cardboard. Cut up some plywood. I have some small rectangles (3" x 4" I think) that I use in my vises all the time. They work fantastic


Old cars are often a pain to wrench on. Just the way it is due to age. Age sucks....

But I challenge you to find an easier car to remove the engine. Only car that rivals the 911 is the old VW Beetle. Some say they can have the engine out in 15 minutes. I believe it. I've seen it done.

[911SauCy]

Thanks for the perverbial typed smack...

I was whining a bit huh.. LOL

I'll be back at it again this evening, grab a big azz wrench in my travels today.

[911SauCy]

So I got this baby apart, some gnarly tooth marks on the caps but they're no worse for wear

However, I think the little tool mark below needs to be addressed as a potential future leak on the press fit surface. Which is why were in this mess in the first place.

[timmy2]

I wouldn't be too confident in it sealing as it should. Unless you have machining equipment...

Tony (boyt911sc) may have a used replacement housing in good condition.

[911SauCy]

This is a used replacement housing I just bought from DC Auto.

I will take a picture of when I am done smoothing out that surface, the aluminum is incredibly soft.

I made some good progress since the photo was taken.

[timmy2]

If you just bought it, you should send it back, unless you made the mark.
Yeah, I know how soft they are. Mine were welded solid after 35 years... The new one works well!