914 thermostat temperature range - what is correct?
 

OK, i'll bite and admit I'm confused.

In trying to troubleshoot an overheating engine and someone suggested checking out the thermostat. Well I could see that it expanded and contracted and operated the air diverting flaps, but I thought "what the heck".

I removed the thermostat and tested it according to the technique on page 13 of the Haynes manual. That says to insert into water and it should become expanded between 65-70 degree C. Well mine did not. It did expand at a higher temperature around 85-90C so I thought Hmmmmm.

Having immersed the thermostat bellows in water cleaned it off and I noticed that the thermostat was stamped 85-90C. AHAH! I thought, this kicks up the engine to around 190F before cooling even gets a chance to start, and since the previous owner had installed a rebuilt engine, perhaps the wrong thermostat was installed.

Now comes the rub. I ordered a new replacement thermostat from my FLAPS and guess what? It was clearly stamped 85-90C. Exactly what I now have.

Am I missing something here? Is this the correct thermostat and the Haynes manual wrong?

Like I said, I'm confused. Can someone shed some light?

------------------

A little bit more information that confirms the Haynes manual. Last night I checked out my shop manual fiche and they also indicate a range of 65-70C that they bellows should open.

There is a difference of about 20degree C or about 68F between the manual and what is on the car.

Am I missing something?

Regards,
Ron Dupre
rdupre@houston.rr.com

My thermostat is also stamped 85-90 degrees.

It was pretty much fully expanded in the mounting bracket with a broken cable so I would think it is bad. I tested it in the 150-160 degree water and it didn't change dimensions. I didn't really notice the higher rating until you mentioned it.

I've got a new one on the way, so I'll write back to let you know what it is stamped.

If I understand it, if the thermostat bellows is fully expanded at room temperature and you can compress it with your fingers, then it is bad and needs replacement.

I'll be curious to see what you get to replace yours.

Well just got my replacement from Pelican.. It is stamped 85-90....go figure...

Believe 1/2 of what you read in Hayes.

Stock thermostat for T-IV is 85-90 degree. Usually when they go bad they expand. Expanding the thermostat opens the dampers on the fan. This is good because an expanded thermo. or a broken cable opens the flaps to allow maximum air flow.

On an carb. model, it takes longer to warm up and on FI it will run but use more gas... Always run a thermostat, it keeps the engine at the best temp. for poerformance. Good luck.

Well, I've come to the conclusion that both the Haynes manual and the 914 shop manuals are wrong about testing the thermostat. Mine is stamped 85-90C and apparently so is everyone else's. It expands between those temperatures, thus it appears to be working as designed.

I've reinstalled the thermostat in the car and will look elsewhere for the source of my overheating problem.

Thanks for all who responded here and directly with email.

Just a suggestion but have you looked for leaves and debris in your fan impeller? There may also be covering the oil cooler under the passenger side cylinder head cooling tin. And if you really dig in pull both side cylinder head engine tins and look for debris on top of the cylinders. I believe one method of making sure the thermostat is installed correctly is to start your 914 and let it warm up to operating temperature. Then attach your themostat cable to the cooling flap linkage. Since the linkage is spring loaded it should automatically force cool air over the oil cooler and skip the warm up process.

HTH

ShawnO,

Thanks for your suggestions. So far to check out my heating problem I've:

1. updated the guage and sensor
2. checked the thermostat
3. exercised and readjusted the flap controls. (I can't see the flaps actually work, but it sounds like they are hitting the stops when I move the bar.
4. Checked for obstructions in the fan and other intakes
5. plugged up the holes in the tin. Put in new spark plug wires with new seals. (they were old anyway and thought it a good excuse to upgrade.)
6. checked timing. I have the petronix ignitor. Timing is dead on. Dwell is 57 degrees, but I understand that it doesn't mean anything with an electronic ignition kit.
7. checked that hot air deflectors are in place under the car.
8. peeked at the bottom of the oil cooler to see if it is dirty/plugged. It appears fine.
9. tightened the alternator belt as recommended although I don't see how that could affect the cooling.

So, it appears that I might be pulling the tin shortly. Too bad, now is the time you want to drive this car in Houston.
:rolleyes:

Ron,
I hate to tell you but I have a stock '76 that I have owned for 3 years and in spite of everything I have tried it still runs too hot. I have tried everthing on your list and pulled the engine tin as suggested but the cylinders were clean of any debris. If you find the root cause, please share your success!

Is the engine stock? Maybe its time to invest in an external oil cooler? I was lucky and my '73 already had one. Good luck!

The T1 thermostat is rated between 65-70.

I imagine Hayes is on crack again or the reference is to a T1 engine somehow? Hayes usually really sucks and is only in business because the manuals are soooo cheap compared to the Robert Bentley books.

I am surprised the T4 thermostat is so high in temperature! I will check the t-stats I have, three I think, tonight as a comparison

I check mine by putting them in the freezer (in the basement so wife does not biatch ;) ) and then place them in the basement oven at 150 degrees to see if they open right.

!!! Always keep the metal shroud around it on !!! If the metal shroud/holder is taken off the t-stat can over expand and burst.

Also I have seen only 1 t-stat fail closed, why I do not know. I suspect the gas was never filled from the factory properly to expand the t-stat open. People say it is impossible to fail closed but that is not true. All the others I have seen in T1 and T4 motors have failed open based on my sample of about 25 t-stats.

You know you might have something there.

Both the Haynes manual as well as the Porshe 914 Shop manual (mine's on fiche so it's a bit more inconvienient to check) say the same thing and indicate the lower temperature. I'll bet that it was originally spec'd with the Type 1 thermostat but when it was all said and done the Type 4 thermostat was installed. And...get this... the documentation was not updated. ;) Being an old software jock, I can see where this would happen.

Any luck Ron?

sounds to me like you have an internaly pluged oil cooler I had one that the wrong O ring was installed (too big) and when tightened down it crush down and make the opening too small so oil would not flow too good.

I would also check the ...fuel mixture (Lean) fuel pressure...regulator... injectors...