89magic98

I installed a new water pump / belts / rollers, etc.

During the install, I tensioned the new camshaft belt to 2.6 using the 9201 tool. It should have been 4.0 +/- 0.3.

I think I did a good job bleeding the system. However, the car now runs between 1/2 and 3/4 marks now, about 1/4 higher than before. Increasing engine RPMs causes the temperature to go down. Fans come on. It seems like the upper radiator hose fills with coolant (as observed by squeezing the hose).

OK, here are some ideas of what I may have done wrong.

1. Water pump pulley is slipping on the timing belt. If this is the case, I need to retension right away before glazing the belt, right?

2. Fan wiring reconnected incorrectly. Aren't the plugs for the fans polarized? Could I have plugged the cooling fan harnesses in upside-down?

3. Incorrect bleeding. I think that I've got all the air out of the system. It was bled with the heat on warm. I don't see any bubbles coming out of the bleeder opening.

4. Thermostat problem. I should have put the old and new thermostats in a pot of water, bringing it to a boil to check that they both behaved the same, but I did not. I don't think this is the problem based on my symptoms.

Any other thoughts?

Thanks for everyone's feedback!

Porsche-O-Phile

What you say makes sense, I'd just open up the front cover and retension the belt properly. When you do (obviously) check the belt condition and if it looks good, that should do it. Slippage does sound like a possibility. 1/2 to 3/4 really doesn't sound that hot though, I'd be more concerned with busting a belt.

austin944

I've received a thermostat that was a higher temperature that what I ordered. I remember the car running hotter and didn't check the rating before installing it. Took it out of the water pump, put it in a pot of hot water and compared it with my old thermostat, and sure enough it opened later. This was from a reputable supplier. I guess mistakes happen.

Bleeding all the air out is a real bitch. I put a pressure tester on the radiator cap, pump up the pressure, and if the coolant level drops in the reservoir, then I know that I've still got air in the system (since air compresses, coolant doesn't).

Fans shouldn't come on during highway driving, so if it's running hotter at speed, the fans aren't the problem.

I tend to doubt it's the water pump pulley slipping. If the belt's on there and the engine is running without problems then the tension on the pump should be OK, IMO.

Eyal 951

My money is on improper bleeding. These cars are a supreme bitch to bleed.
~Eyal

Dal Heger

#3, no question. Bleed it properly.

These cars are NOT tough to bleed. Do a search and you'll find the proper (easy) procedure documented many times. I have documented it at least twice (I'll type it out again if needed, but I'm lazy right now).

Dal.

Peckster

Come on Dal, save it on your desktop so it's handy.

89magic98

My old thermostat says 80 degrees C on it.

I am looking at the box that the new one came in. It is a Wahler thermostat, part number 4256.83D60. It supposedly was Porsche part number 944.106.129.05. I did not read what was written on the new thermostat before I installed it.

Does this mean that I replaced what I had with an 83 degree C thermostat?

brad-cam

The standard Wahler thermostat is 83 degrees. The white lines on the temp gauge are 80 and 100 degrees. Mine runs about a quarter of the way from the bottom line to the top line, which makes sense.

89magic98

My old one has 80 degrees stamped on it.

Was I using a non-standard thermostat before this point?

Would the 83 degree thermostat have "83" stamped on it?

austin944

Yeah, they're stamped with the temperature. I found my old Wahler thermostats, have an 80, an 83, and an 87. The 87 was in a box with the 944.106.129.05 part number, though I have another box with 944.106.019.00 with an 80 thermostat in. Can't remember whether they're in the right boxes or not.

IPSC

my money is on the thermostat. I went through this same thing myself. Bled the system till I was BLUE in the face. turned out the thermostat was not even beginign to open till 212 degrees F. changed to a lower temp and WA LA it has been fine ever since.

IPSC

89magic98

I guess I will call Zim's tomorrow and ask if they sold me an 83 degree thermostat. They stated it was a "standard temperature" thermostat. The factory manual only mentions an 83 degree thermostat, so I assume that 83 degrees is "standard".

Another question (or two):

1. Doesn't the fan switch and the thermostat have to be a matched pair (from a temperature standpoint)? What happens when you go from a matched pair to using a thermostat that opens at a higher/lower temperature?

2. I am beginning to believe that going back to the thermostat temperature I had might fix the problem. However, am I also dealing with a radiator that should be replaced? These cars ran fine (when they were new) with 83 degree thermostats and new radiators. In other words, would a new radiator also fix this problem? Does the 80 degree thermostat "mask" the issue of a older (less efficient radiator)?

Thanks for the input guys!

Dal Heger

What part of this problem sounds like a bad thermostat?
The radiator fan switch will turn the fans on when it needs to (it doesn't matter if it's a matched set, 80C or 90C or whatever). Besides once you're moving more than 30 mph the fans don't do anything, all the cooling is done by the ram air coming through the rad based on your road speed. If there is air in the system, then the thermoswitch isn't in contact with the coolant, it won't turn on.

If your radiator is plugged then no matter what you do, your car will overheat. It won't matter if you rev the engine and try to pull more coolant from the rad.

It's not bled properly.. the quote above gives you the answer to the problem without even thinking about it. The upper radiator hose should be filled with coolant ALL THE TIME! The cooling system is a closed system, there should be NO AIR in it.

Ok, The EASY way to bleed...

1) Make sure that the car is on a level surface.
2) Open the bleed screw
3) pour in the coolant/distilled water mix until it comes out of the bleed screw (yes, it will be well over the "full" mark on the reservoir)
4) close bleed screw, leave the cap off of the reservoir
5) start car
6) turn the heater control to FULL HEAT, turn the fan on to 4.
7) let the car heat up, the coolant in the reservoir will burp and go down as this is happening
8) you may rev the engine to get the engine to heat up faster and to get it to open the thermostat
9) Once the thermostat opens (the reservoir will burp and the coolant level will decrease) add more coolant
10) let the engine continue to run to fully warm up. Keep adding coolant as needed.
11) You can rev it a little to move the coolant/any remaining air out of the system as needed.
12) once the radiator fans have cycled at least twice (on-off, on-off) and the reservoir is not burping air anymore, fill to the full line or above and put the radiator cap back on.
13) you're done.

Use a good (no silicate/no phosphate) antifreeze and distilled water in a 50/50 mix.

I've done this many times and it works well. Be sure to wash down the area with water to make sure no animals lick up any spilled coolant. You WILL spill coolant.

As with any scalding hot liquid, be careful.

There is one even easier way to fill a cooling system with 0% chance of trapped air, but you need an air compressor to pull a vacuum in the cooling system, but I won't get into that.

Check the simple things first.

good luck.

Dal.

89magic98

Update...

...turns out there was some air in the system. I removed the cap and bleeder screw, and filled the reservoir until it came out of the bleeder bolt hole. This has improved the operating temperature somewhat. I will recheck this again today.

It still looks like it is running a little hotter than it was before.

I have another question though. Assuming nothing else changes (properly bled system, all other parts identical), the operating temperature range of the car is different with 80 and 83 degree C thermostats, right?

89magic98

OK, Zim's confirms that it is an 83 degree thermostat.

So, one more question:

- Assuming the car has reached operating temperature, is the thermostat constantly open? Or does it cycle between open and closed?

Thanks again everyone!