Thermostat Valve Opening Test....

[boyt911sc]

I'm in the middle of installing an auxiliary thermostat for my '78SC. The 'old' thermostat was damaged during the removal process and was beyond repair. So a replacement thermostat was obtained from a dismantler and its in very good condition.

I would like to do a test before installing it on the car. The thermostat unit has been dismantled and ready for assembly. Could someone tell me how the test is performed? Thanks.

TD

[schulr]

Which thermostat are you speaking of? If its the one in the wheel well, put it in hot water and see if the tit rises. This should indicate that its ok.

Bob

[Grady Clay]

I think the important issue is that it starts to open at a certain
temperature and it is fully open at another higher temperature.
It then should close in reverse order as the temperature cools.

Since this thermostat-pipe-cooler arrangement is basically the
same from ’74 through ’89 it is worth some detailed discussion.

For reference the 911R had the only front cooler prior to ’69
911S. The ’69-’71 were basically all the same. The ’72 was
unique to that year. The ’73 was unique to that year and had a
pressure relief at the oil tank. The front cooler system was also
on all Sportomatics (905 & 925) from ’69. With the correct set
of parts, this system can be fit to all 911s '65-'89.

Here are some excerpt Factory images to use in the critical discussion:

IMAGE OilThermostat74a.jpg "
"
© Dr. Ing. h.c. F. Porsche A.G.



IMAGE OilThermostat74b.jpg "
"
© Dr. Ing. h.c. F. Porsche A.G.



IMAGE OilThermostat74c.jpg "
"
© Dr. Ing. h.c. F. Porsche A.G.



IMAGE OilThermostat74d.jpg "
"
© Dr. Ing. h.c. F. Porsche A.G.



IMAGE OilThermostat74e.jpg "
"
© Dr. Ing. h.c. F. Porsche A.G.



I need to clean up and annotate the images with the Edit function.
It has been many years since I did this and we should get ALL
the details correct – no misinformation.
If anyone finds anything wrong or not clear – please say so.

Best,
Grady

[boyt911sc]

Grady Clay,

I just inspected my partially disassembled auxiliary thermostat and it seems that the oil from the engine will flow directly thru the thermostat housing flowing back to oil tank and to the auxiliary cooler and back to the thermostat(valve close). Is my assumption correct?

I'm still having some difficulties visualizing the closing/opening of the thermostatic valve. Could you kindly help me understand the this set-up? Thanks.

TD

[Jubbie]

I tested my engine thermostat in a pan of motor oil over a stove top. At ~195degF, based on a meat thermometer, it would open if it worked.

Check this link and the links in the link
Well worth it to check thermostat

[Grady Clay]

TD,

Can you post some digital pictures of your thermostat? Are you able to unscrew the thermostat and pressure relief end plugs on your old thermostat assembly? In IMAGE “a” #1, #2, #3, and #4 are the thermostat parts. IMAGE “a” #5, #6, #7, and #8 are the pressure relief parts.

I think your assumptions are correct but I want to see the internal passages. I don’t think you want to disassemble the thermostat assembly to measure the just-opening and full-open temperatures.

Friday I’ll try and find a defective one also.

Best,
Grady

[boyt911sc]

Grady Clay,

I was able to removed all the components of the thermostatic valve and pressure relief valve except #8 from the housing. Since my interest was more on the temperature valve movement, the removal of part #8 was not pursued. Part #8 refused to slide out easily unlike the thermostatic valve.

So how do you check the thermostatic valve opening/closing? Will water bath test used for the engine thermostat work?

If my assumption is correct, the opening of the thermostatic valve allows the oil to flow back to the oil reservoir/tank. Thus oil cooling from the auxiliary cooler is carried out when the valve is opened(????). When the valve opens, is the oil flow partially or completely diverted to the cooler????? Comments please.....

I simply want to understand how this external thermostat unit operates. TIA.

TD

[vash]

i THINK it opens/shifts at 180 degrees so water will work.

IMHO, it isnt that hard to take back off, especially if you just installed it. fittings dont freeze that fast. i just installed mine, and tested it on the car. i didnt feel good about taking things apart, and voiding my salvage yards warranty, stripping anymore fittings, leaks, etc...

just my opinion.

[Grady Clay]

Well, I found a thermostat assembly for us to experiment with.
Needless to say the threads are trashed on two ports.

IMAGE OilThermostat74f.jpg


IMAGE OilThermostat74g.jpg


I also found a cool thread repair part:
IMAGE OilThermostat74h.jpg


IMAGE OilThermostat74i.jpg



You can check that the thermostat element functions by
measuring its length at various temperatures. I’ll do that soon.
To find out the two critical temperatures (first opening
temperature and full-open temperature) we need to test the
thermostat element in the housing.

My scheme is to use a clear cooking oil so there aren’t any little
bubbles. I’m going to take images down the “return from cooler”
port where the temperature regulating is done. I’ll need to
make some “peanut” light bulbs soldered on wires to get light in
the right places. My taking images 80 mm down a 20 mm port
will take some work.

IMAGE OilThermostat74j.jpg


Best,
Grady

[vash]

grady! we need to change your bbs title to "WIZARD". wow.

[Jascha]

Hi Grady...

Can you suggest how one can best remove the end-plugs on the external oil cooler thermostatic plunger. You posted some very nice pictures explaining the circuit

I see that both aluminum cap slots are 'stressed' which may make removing within the wheel well a challenge... I was thinking of clamping an old coin (hexagonal 50 pence piece -avoiding demaging the crown) in a Wise-Grip and trying to pry it that way...?

Cheers,
Jascha

[safe]

I recently did this job.
I made a tool that fitted perfectly and still I didn't get the caps of...

Then I used the tool that never fails, a pipe wrench. Got the caps of in no time. Just use one with sharp teeths and adjust it right.

I had my thermostat in a vice, if yours is still on the car you might have problems.

[Early_S_Man]

Grady,

Didn't the artist/writer reverse the positions of the flow arrows and labels in your diagram 74d in the factory service manual??? The flow arrows are correct in your diagram 74e, as the hoses and pipes are visible [on the whole page view] all the way from the 911/83 MFI engine to the trombone cooler ... and the inboard circuit of the thermostat assembly is from the scavenge pump and to the cooler, not as labeled in 74d!

It would seem that the artist got confused in converting the drawings to a vertical layout that could be printed on the smaller page!

Also, aren't the plungers mislabeled in the factory list of components for your diagram 74a? The plunger #4 is clearly the same type used in the 1973 tank-mounted pressure relief valve. The plunger #8 style was not present in the 1973 design.

[Jascha]

I tried my luck using every tool (and weapon) in my armamentarium to remove the end-plugs while confined to the wheel well. I even tried turning the slotted cap (naively!) clamping a 50 pence coin using Wise-Grip –hopefully the QE will forgive me (no damage done to the embossed head-crown).

It seems as you also point out, these end-plugs are impossible to dislodge without the removing the full valve-housing assembly. I was gratified being able to remove it with little effort (PB Blaster was of much help). I clamped the valve housing in a wise and used a potable (14.4 Volt) impact wrench (~ 66 ft-lb) and wedged driver socket (Snap On) which made it possible (after some effort) to remove both end plugs. I also used an impact driver but could not get the end-cap to budge.




The take home message: if at all possible, remove the valve housing and do the rebuilt on the bench.

[boyt911sc]

Originally Posted by Grady Clay

TD,

Can you post some digital pictures of your thermostat? Are you able to unscrew the thermostat and pressure relief end plugs on your old thermostat assembly? In IMAGE “a” #1, #2, #3, and #4 are the thermostat parts. IMAGE “a” #5, #6, #7, and #8 are the pressure relief parts.

I think your assumptions are correct but I want to see the internal passages. I don’t think you want to disassemble the thermostat assembly to measure the just-opening and full-open temperatures.

Friday I’ll try and find a defective one also.

Best,
Grady

Grady,

It has been a long time since I posted this thread several years ago. But I would like to share some findings regarding the oil flow in an auxuliary thermostat.

1). The opening to the oil line to the auxiliary cooler (Carrera cooler) is always open.. Meaning wide open all the time and no valve involved.
2). When the oil temperature gets high (warm) to about 180 F plus, the auxiliary thermostat comes into play.
3). The initlal cooling process of the engine oil is controlled by the internal thermostat in the motor and circulated thru engine oil cooler then to the oil tank.
4). When the engine oil gets up to around 180 to 190 F, the oil return opening (oil from the auxiliary cooler) starts to widen. Thus an inital flow of oil thru the auxiliary cooler is experienced for the first time.
5). Simultaneously, as the opening for the return oil (auxiliary cooler) increases, the valve opening for the return to the tank decreases. When the oil temp. is below the opening temp. of the auxiliary thermostat, the valve opening for engine to oil tank (let's call this as A) is fully open (100%) and valve opening from the auxiliary cooler (let's call this B) is 0% (fully closed).
6). As A starts to close, B begins to open. The openings for A and B is the same. In simple description, when A is 100% open, B is 0% open. When A is 90% open, B will be 10% open and so on.
7). The change in valve opening ratio will proceed as temp. goes up till valve A is fully closed (0%) and valve B is fully opened 100%. Valve opening is temp. dependent.
8). Don't know when valve B's maximum opening occurs. But at temp. below 180 F, valve B was fully closed.

Just wanted to share my findings from the tests made. Not very scientific but practical. Comments, remarks, critics, etc. welcome.

Tony

[patkeefe]

As this is topical to me at the moment, I will describe the problem I am currently having:

I had my aux stat out and checked the thermostatic operation about six months ago; works as it should. However, I have had a bit of a very high temperature issue. So, today, I got the car warmed up really well, and got my digital thermometer out.

The line from the engine to the aux stat is at 200F. The lines to the fender cooler are both at the same temperature, relatively, right around 200F. This indicates to me a lack of heat transfer, and probably a lack of flow. Now, the line from the aux thermostat to the oil tank is about 140F, unless measured in close proximity to the oil tank or the thermostat, which indicate a much more relatively close temperature to the body of the stat or the oil tank itself.

I am thinking my bypass may be stuck, but I am unsure of how the bypass valve functions. I know the thermostat works, as the lines are cold until I get the temp up around the operating range of the thermostat. So, does the bypass function strictly as an over-pressurization safety dvice.

Thanks!
Pat

[Jascha]

Pat,

When the car is not moving very little heat transfer will take place (both oil lines will be nearly at same temperature) leading to the front oil cooler.
(I gather you don't have a temperature activated fan on the front oil cooler)

The 'bypass' is basically a high pressure valve (spring loaded piston) that is intended to protect the front cooler from rapturing... it rarely fails unless the spring snapped

It seems improbable for the return line from the external valve back to the oil tank to be @ 140 deg if indeed the bypass stays open at all times...you need to measure the oil temerature in the tank to help make sense of this.

[patkeefe]

The oil tank temp was approximately 200F also. Jascha, you are absolutely correct on the non-moving vehicle. I basically jumped out of he car before with the infrared gun in my hand to take the measurements. I don't have a fan in the brass Carrera cooler. As I had mentioned, I did have the stat out and apart a while back, when I rebuilt the engine, and everything looked fully functional to me at the time. I also have a turbo on the 3.0 (the car is an SC), so I am concerned with a bigger heat load than most.

I do have a four temperature probe meter, which I can get differentials with. I'll try hooking it up tomorrow and see what's what. I also agree that the 140F number is so weird it defies logic. Be on the lookout for an SC with wires duct taped to the door and fenders!

[boyt911sc]

Pat,

The Carrera cooler is not sufficient to cool your 3.0 liter turbo engine. At best, it would be in the high temp. range. The auxiliary thermostat could be tested without removing the end caps.

The complete aux. thermostat (less the oil lines) is easy to test in a water or oil bath. Having observed the movement of the valve in the thermostat, will assure you that you have a working unit. Just my two-cents.

Tony

[patkeefe]

Tony:
You should have stopped by last month, I could have used a hand!

My 3.0 fried at Summit Point in 06 due to a bad engine (internal) thermostat, so I'm pretty sensitive to oil temps. The stats in the car have been tested on the stove. Here is the little Mocal I was using.

(well, I can't upload any photos at the moment; maybe later)

I suggest we discuss the merits of the Carrera cooler on the links soon.
Pat

I put the results here:
http://forums.pelicanparts.com/porsche-911-technical-forum/361666-front-oil-cooler-high-oil-temps.html#post3423094