External Thermostat Rebuild --- yes I have searched!

sempaipaul · 01-20-2014, 05:59 PM

Guys,

So we only rebuild one of the pistons in the external thermostat? Why not the other?

... this may be a dumb question --- I am currently ordering that one piston as I am overhauling the whole oil system and figured a 34 year old car may benefit from this.

Here is what I have so far in my shopping cart:
Pelican Parts - Product Information: 930-107-155-00-M322

Pelican Parts - Product Information: 900-123-136-30-OEM

Thanks!
Paul

sempaipaul · 01-21-2014, 08:40 AM

anyone?

KTL · 01-21-2014, 09:07 AM

You don't rebuild the other because it is not a regulator (with internal moving parts) like the part you are replacing. The other piston is a pressure bypass fitting that only operates with overpressure. So basically the other piston is just a hunk of plastic that is put into action when pressure overcomes the spring resistance. I'll take a picture of the overpressure piston when I get home.

By the way, if you're rebuilding t-stats? You may want to look at rebuilding the t-stat in the engine. It uses the same regulator. Check out this useful post from burgermeister Frank.

internal oil thermostat repair

sempaipaul · 01-21-2014, 09:13 AM

Quote:

Originally Posted by KTL

You don't rebuild the other because it is not a regulator (with internal moving parts) like the part you are replacing. The other piston is a pressure bypass fitting that only operates with overpressure. So basically the other piston is just a hunk of plastic that is put into action when pressure overcomes the spring resistance. I'll take a picture of the overpressure piston when I get home.

By the way, if you're rebuilding t-stats? You may want to look at rebuilding the t-stat in the engine. It uses the same regulator. Check out this useful post from burgermeister Frank.

internal oil thermostat repair

KTL - Thanks for your response. Not rebuilding the engine T-stat as not taking engine out just yet. I'll be doing a full overhaul on that starting in the fall. I am trying to get everything else sorted before I pop out the engine for now.

Ok so I don't need to get (the bottom one):
Pelican Parts - Product Information: 930-107-076-00-OEM
as I assume that never goes bad;

but I should get (the side one):
Pelican Parts - Product Information: 930-107-155-00-M322

and the seal for it:

Pelican Parts - Product Information: 900-123-136-30-OEM

So I shouldn't disassemble the bottom one to clean either? or should I still disassemble it and put a new seal on it?

Thanks again!
Paul

KTL · 01-21-2014, 09:18 AM

Yes in my opinion you don't need to replace the bottom fitting (pressure bypass). But by all means YES open it up to clean. If you have a t-stat of unknown usage, you never know what it's been subjected to.

When my engine failed a few years back due to an oiling issue, it wasted all the main and rod bearings (along with other engine parts) and I disassembled the t-stat to ensure no debris was in there. I threw away the temperature regulator & installed a new one. Opened the pressure bypass side and found a small amount of debris in there as well.

sempaipaul · 01-21-2014, 09:27 AM

Quote:

Originally Posted by KTL

Yes in my opinion you don't need to replace the bottom fitting (pressure bypass). But by all means YES open it up to clean. If you have a t-stat of unknown usage, you never know what it's been subjected to.

When my engine failed a few years back due to an oiling issue, it wasted all the main and rod bearings (along with other engine parts) and I disassembled the t-stat to ensure no debris was in there. I threw away the temperature regulator & installed a new one. Opened the pressure bypass side and found a small amount of debris in there as well.

Thank you much!

Regards,
Paul

boyt911sc · boyt911sc's Garage

Paul,

Why do you think you need to rebuild the auxiliary thermostat? If I were in your shoes, I would test it first before buying replacement parts. You might not need to replace the slide valve (thermostat).

Things you have to consider at this point:
1). Do you want to remove the auxiliary thermostat from the car?
2). Or do it insitu?

Looking at the above picture, the thermostat (slide valve) is shown at the left side and the pressure relief valve is at the right side. Most of the time, the failure mode was caused by the slide valve (thermostat). And have not encountered one with a bad pressure valve.

Tony

sempaipaul · 01-21-2014, 10:19 AM

Quote:

Originally Posted by boyt911sc

Paul,

Why do you think you need to rebuild the auxiliary thermostat? If I were in your shoes, I would test it first before buying replacement parts. You might not need to replace the slide valve (thermostat).

Things you have to consider at this point:
1). Do you want to remove the auxiliary thermostat from the car?
2). Or do it insitu?

Looking at the above picture, the thermostat (slide valve) is shown at the left side and the pressure relief valve is at the right side. Most of the time, the failure mode was caused by the slide valve (thermostat). And have not encountered one with a bad pressure valve.

Tony

Tony - I am overhauling the entire oil system (except for the engine thermostat). I have it all disassembled and apart as I was also fixing some crushed oil lines and put on a 28 row brass cooler on the front.

I figured it was only fair that I give the thermostat a rebuild considering its all 34+ year old stuff.

Thanks for the picture. I ordered all the stuff from Pelican. I figured since I have it all apart - I might as well do it now.

Thanks,
Paul

Matt S. · Matt S.'s Garage

Paul,

Thanks for asking this question. I too wondered why only the slide valve was available and not the pressure relief valve.

I am getting ready to take my external thermostat apart to replace the slide valve as my lines going to the thermostat get hot but my lines going from the thermostat to the trombone cooler remain cold. Tony, thanks for the picture and for other posts I have followed you on.

Good luck Paul,

Matt

fintstone · fintstone's Garage

Do yourself a favor and don't remove the thermostat from the oil lines unless you have to. Many thermostats and lines are ruined that way. Just repair I place or drop the entire line for better access.

911SauCy · 911SauCy's Garage

Quote:

Originally Posted by fintstone

Do yourself a favor and don't remove the thermostat from the oil lines unless you have to. Many thermostats and lines are ruined that way. Just repair I place or drop the entire line for better access.

THIS.

Exactly why I ended up getting an external t-stat from DC Auto. Went to replace the original/leaking lines from the engine/tank, used pb-blast and heat...threads still came off the t-stat housing.

I tightened it up, but in time the leaking started as a drip...then, when hot, became a flow...

KTL · 02-05-2014, 01:32 PM

The key to saving yourself from having to buy an entire t-stat (when you break it by screwing up the threads) is to cut the oil line off. You cut it off by splitting the nut with a cutoff wheel.

The threads are usually damaged by stress, not corrosion. What happens is the oil line gets frozen onto the t-stat by the collar nut being clogged with crud where the oil line enters the back of the nut. When you try to loosen a crudded nut and the nut does not turn on the threads, due to the load placed on the threads by its tightness, the oil line itself spins since it is the path of least resistance. So you've got a loaded nut turning on the aluminum threads and guess what happens- the threads strip.

So you either throw away the t-stat if you really messed up the threads bad, or you use the thread saver fitting.

Porsche 911 & Carrera Oil Circulation - Page 4

To avoid having to repair a perfectly good t-stat (besides it having a faulty temp regulator), you just cut the nut. Or strike the nut & oil line with a rubber mallet or dead blow hammer, hoping to break up the crud that's frozen the nut. The sucky part of the nut cutting is that now you've disabled your oil line and you need a new nut! So then you have to either: 1) re-hose the line to install a new nut (or good a used nut- I save the good ones) or 2) you use one of Elephant's ingenious solutions

Elephant Racing | 30mm Oil Line Tube Nut Replacement Kit | Porsche 911

I would suggest anybody buying a good used t-stat should take the time to put a new regulator in it while you have it removed from the car. That'll save you the hassle of taking it out a year later when the regulator goes kaput. I'm not saying it's a fact that the t-stat regulator craps out regularly. I'm just saying that Murphy's Law occasionally holds true after you've put a lot of work into something.

Murphy's Law: Anything that can go wrong usually will.

Murphy's law - Wikipedia, the free encyclopedia

Years ago my dad (RIP) had a plaque of Murphy's Law on the control panel/"helm" of his houseboat. My dad, as good as a guy there was (i'm biased of course), had more than his fair share of bad luck with mechanical stuff. Especially his boats. Despite him being a great mechanic/wrencher who took good care of his cars & boats, Murphy always picked on him.

I'm glad I got my fill of boats at an early age & I don't want one. Best two days of owning a boat are the day you bought it & the day you sold it!