External Oil Thermostat

DonE · 08-13-2009, 07:22 PM

I went on a 5 hour mountain drive today and on the way back, I noticed my oil temp climbing to 235. I slowed but it kept rising, so I pulled over to let it cool. I also noticed while I was sitting, my oil quantity gauge showed nothing. So, while it idled, I checked the dipstick - no oil. Hmmm - I just put a quart in before the trip. I went around to turn the motor off and the gauge showed 2/3's. WTF.... I went back to the dipstick, checked, and it was right where it should have been. I then looked at the temp, and it had already started coming down. So, I got back on the road watching the temp and it went back to normal (about 190). About 15 min later, the same thing happened. I pulled over and this time tapped the external thermostat with a big rock. Within a couple of minutes, the temp started dropping.

I got the car home OK and took the thermostat apart and found it was stuck half closed. It took a screwdriver to break it loose where the plunger would work. I think I'm gonna gut it and drive on. Are there any aftermarket solutions out there that work?

kellcats521 · 08-14-2009, 03:09 AM

Hayden sells one on page 8 here. They have a good reputation, but 3/8" fittings might not move enough oil for us....

WERK I · WERK I's Garage

Don,
When I rebuilt my engine, I had to replace the external thermostat because I broke some threads on it during oil line removal. I purchased a replacement from our host and I ran into the same problem as you did. I removed the new thermostat and dumped it into a pot of boiling water......sure enough, port only opened half way. I gutted the new thermostat as well as the old one and removed their respective paraffin cartridges which control the valve opening temperature and distance. Put the old cartridge into the new housing and tested again. Worked fine and is still working after 5 years.
I know our host had nothing to do with this issue, they get their parts from Porsche. And I wasn't about to send the defective thermostat back and wait another 2 weeks

before I could get the car on the road waiting for parts. I do think these are extremely reliable units and flow well, but are there issues with the Porsche vendor's QA?

930gt-40r · 930gt-40r's Garage

Thermostats suck when they have problems- mine thinks it is ok to bypass the oil cooler randomly (the bypass hangs up occasionally..)
How often are the t-stat inserts bad from the factory? I need to replace that and I need to replace the bypass/spring.

A930Rocket · 08-14-2009, 08:41 AM

Do all new T-stats do this? I had to replace the guts of my new one years ago with pieces of my old one as well. For that kind of money and building it for 30+ years, you would think they would get it right.

DonE · 05:32 PM

Quote:

Originally Posted by kellcats521

Hayden sells one on page 8 here. They have a good reputation, but 3/8" fittings might not move enough oil for us....

You might be right since the stock unit is between a -12 and -16 line.

DonE · 08-14-2009, 05:32 PM

Well, I spoke to about 6 different people today (although most everyone seems to be in Monterrey) and I ended up buying a used unit from DC Automotive after stripping the threads on the original piece (or should I say POS). I intend on gutting the unit from the get-go so all I am interested in are the threads on the cast aluminum. I even took all my hoses and the thermostat housing to Summit Racing and we spent about 30 min trying different ideas but they didn't have anything in metric. I then went to a custom hose maker and they couldn't match the stock threads nor could they find any fittings for the hard lines (in case I wanted to convert to AN fittings).

Since it's 90+ degrees in Atlanta until Oct, I'm not gonna worry about warming the engine up too slow. In the mean time, I'm going to find an inexpensive fittings solution using -12 AN fittings and our host's Mocal thermostat for $128.

GJF · 08-14-2009, 05:47 PM

Don try BAT Inc. They sell a external unit that is -16AN. I have been using these for years and never had one fail.

GJF · 08-14-2009, 05:51 PM

930gt-40r · 930gt-40r's Garage

Don- for your car I wouldnt use anything less than a -16

930gt-40r · 930gt-40r's Garage

How many quarts of oil does your setup take?

Quote:

Originally Posted by GJF

GJF · 08-14-2009, 06:22 PM

About 6 gallons total but I run 5 gallons with a gallon to spare. The tank actually fits all the way down in the smugglers well, and exits through the passenger footwell.

DonE · 08-14-2009, 06:28 PM

Quote:

Originally Posted by GJF

About 6 gallons total but I run 5 gallons with a gallon to spare. The tank actually fits all the way down in the smugglers well, and exits through the passenger footwell.

I'm sittin here with a big f'ing smile on my face looking at your masterpiece wondering what kind of automotive freak you are.... It rivals the space shuttle but I bet your's leaves on time... Damn dude.

DonE · 08-14-2009, 06:29 PM

Quote:

Originally Posted by GJF

About 6 gallons total but I run 5 gallons with a gallon to spare. The tank actually fits all the way down in the smugglers well, and exits through the passenger footwell.

That explains the GT3 pump.

GJF · 08-14-2009, 06:44 PM

Ya know I never thought of it that way......... FREAK??????? Hmmmmmmm..... I thought everybody here........was one? Hah you and Gabe have me beat. LOL

930cabman · 08-15-2009, 03:14 AM

I just purchased a 1975 911S from a fellow site member and it seems like a great car. It has a radiator type front fender mounted cooler with fan. I drove the car thru the desert last wknd. about 90+ F ambient, about 3800 revs and 85-90 mph and the gauge was reading about 210. Another ride with the ambient about 80 and lower revs the gauge would not reach 180. Perhaps the t-stat is missing or stuck open.
Thanks for the feedback.
John G

930gt-40r · 930gt-40r's Garage

Quote:

Originally Posted by GJF

About 6 gallons total but I run 5 gallons with a gallon to spare. The tank actually fits all the way down in the smugglers well, and exits through the passenger footwell.

DAMN!!!! Thats a lot of oil.
Does your car ever reach operating temp or does it just take forever to warm up- got to get creative with the ignition map to try to get the temps up on warm-up.

Too cool

GJF · 08-15-2009, 02:50 PM

No the T-stat works very well. I fire her up and it takes about 10 - 15 mins to get her up to temp. No crazy creative maps or anything. It is the nice thing about the Mocal T-stat, it actually works the way it is suppose to. I was a bit concerned at first mounting it in the front of the car, but it has been rock stable ever since installed. I does take longer to get to temp in the winter though. Usually race prep cars run this much oil. I could have gotten away with 3.5 - 4 gallon tank but it is done and it works well.

slow&rusty · 08-16-2009, 05:18 AM

I used a Permacool external T-Stat on my Datsun Z turbo and it is very similar to GJF's Mocal unit. It uses 1/2" NPT female ends and runs about $40 from Summit Racing.

Yasin

DonE · 08-16-2009, 09:38 AM

A short update.

I pulled the t-stat and replaced it with a used unit from DC Automotive. Before I installed it, I opened it up to make sure everything looked good and it did. I then tracked the path the oil would take when the t-stat opened. To my surprise (kind of), the path is no more than 7/16 (at most) in diameter around the plunger. WTF? Here we have something between -12 and -16 lines coming in and out of the damn thing only to find a huge restriction inside. I think for our high HP motors, part of the SOP should be to install something like a MOCAL -12 t-stat as part of the upgrade. It's too bad you can't just pull the plunger inside the stock unit and go. Unfortunately, the oil will only circulate back to the engine (path of least resistance).

Tomorrow, I'm going to call Elephant racing to make up a couple of adapters to fit the MOCAL and trash the stock unit.