Alabama Sam

Thomas Ryan:

That's good advice. The pump, belts and rollers, however, are only 10,000 miles old and I'm sure they're genuine Porsche parts because the PO, an MD, was meticulous about maintenance. (He even installed new lower A arms not long ago and the handling is like new.) I have the upper timing cover off and per the advice of Clark's garage I have painted a white nail polish line across the shaft and the pulley, so if the shaft is spinning in the pulley the lines will separate. If the thermostat checks OK but I still have the same problem of running hot when I fire it back up I just have to remove the timing cover to see if the pump is turning. I am led to believe by another post somewhere that if the pump has lost its blades or vanes or whatever they're called I would be hearing very expensive sounding noises.

The Mercedes thermostat on a thermostat is fascinating and worthy of adoption, given the nightmare of bleeding our cooling systems. The Porsche dealer wants 10 hours labor to just to change the thermostat, which explains why I was under the car after dark last night with a spelunker's headlamp strapped to my forehead, and also probably explains why Porsche doesn't follow the Mercedes lead on this part.

Fingers crossed. Stay tuned.

drive135mph

the pump being so young I would agree it's unlikely it failed however I once had a old ford straight 6 water pump shed it's impeller after 12000 miles. Casting mistakes find all manufacturers sometime

Alabama Sam

I have three different thermostats. One is new genuine Porsche (Wahler) 83 degree, one is a new Laso 80 degree model, and one is a new no-name with no rating that my mechanic got from Advance Auto Parts when he couldn't get the lower radiator hose to warm up using the then-new Laso unit when we first buttoned it up with the new radiator and hoses. I have not yet installed the genuine thermostat.

FWIW the genuine part is better looking and appears to be more robust than the other two.

Tonight I boiled all three thermostats. At first I boiled them separately a couple of times, and then side by side. They all opened and at first I thought they were all acting the same, but on closer examination, when the Laso and the no-name begin to close as the water cools down the metal discs on the engine side of the thermostat remain extended far longer than is the case with the genuine thermostat, which backs off of the fully extended position much more quickly. When completely cool the distance between the engine-side metal disc and the sealing ring on the radiator-side is exactly the same for all three thermostats.

I don't know what this means, if anything. I'm not a mechanic. I'm just a guy with a toolbox who can read and follow instructions. I have a car I love that I cannot afford to drive if I have to pay dealer prices for labor. Any wisdom or even educated guesses will be greatly appreciated.

At this point I'm inclined to button it back up using the genuine Porsche thermostat, do my dead level best to purge the air from the system and see whether the lower radiator hose gets warm. I know it might be the water pump but I don't feel like tearing it down in order to get to the pump to inspect it, because (a) I've never personally replaced the belts and (b) I'll have to buy one of those belt tension setting devices and a flywheel lock in order to do it.

mikey_audiogeek

If it's a plastic impeller pump then there will be no warning noises and no damage, just overheating. That's what happened to mine.

Alabama Sam

I have spent some time on the internet looking for an image of the business end of a 944 water pump, in particular, a genuine Porsche water pump, since that's what I think I have, so I can look at the impeller. So far no luck. Can anyone tell me whether the genuine pump has a plastic or a metal impeller?

austin944

Early style pump I had lying around (from Zims Auto). Definitely metal. You said you had an '89, right? Which I think would be late style.

Alabama Sam

Austin:

Thanks, man. That's exactly what I needed. The inside of the radiator side of my pump (where the thermostat goes) looks very clean. No debris or residue of any kind so it seems unlikely it has come apart. I turned the pump and it rotates smoothly. I can't believe I have a bad pump (as I said earlier it looks like a brand new factory unit) so operating on the assumption that my cold lower radiator hose was due to a failure to get all the air out, I'm putting it back together without pulling the pump, after I drill the 1/8" hole in the thermostat. I don't see any downside to this hole. It may take a little longer to get it up to operating temperature, but after that it should function as normal.

Lapkritis

There are some coolant-safe greases that you can use to lube a thermostat. Krytox is what many OEM's use. It won't hurt anything if you have some handy and apply to the moving parts. Also be sure you orient the thermostat correctly during installation... don't want it in backwards. I don't have a 944 unit in front of me to check clearance but I've seen the mistake in other makes before. The 1/8" hole will make bleeding easier but also a potential for overcooling in cold weather. Not a huge deal as you say though. Look forward to your inevitable solution.

Alabama Sam

Got it all back together and running today.

I did all these things learned here and elsewhere to try to solve the "problem" of my cold lower radiator hose:

** Bought Snap On snap ring pliers, Part No. SRPC9045A, 45 degree bend, .09 tip, $33.00, plus shipping. This gets the snap ring out FROM THE BOTTOM, but you have to use two hands. A pox on whoever said you can get it out from the top. No, you can't, unless perhaps you remove the whole front end so you can see the thing.

** Bought a new genuine Porsche thermostat from the dealer; tested same; installed same. I also tested the thermostat that was in the car when all this started. Both tested out just fine.

** Bought Krytox high temp grease - $15.00, plus shipping, for half an ounce. Smeared it all over the thermostat.

** Drilled 1/8" hole in the thermostat rim, which is a trick used by Mercedes and Honda, among others. Oriented the hole at the top when I installed it. Supposedly this lets the air get past the thermostat and up to the bleeder.

** Bought a packet of 8 MM grease Zerks, in order to run a clear hose from the bleeder fitting to the overflow tank (and I installed a new white OEM tank just for this occasion). This is a much more efficient air removal remedy than any other, but I was unable to drill out the Zerk mechanism - its incredibly hard - so I just stuffed the clear hose in the bleeder hole and held it in with my hand and put the other end in the tank. It was very gratifying to watch alternate bursts of air-coolant-air-coolant-air-coolant flow from the bleeder to the tank as I revved the engine, which eventually became nothing but coolant. I don't think there's any air in my system after all that.

Went for a test drive. Drove 50 miles with heater fully on, some town driving but mostly at moderate highway speeds. Ambient temp 75 degrees F. Temp gauge never went above halfway between the lower and upper white marks. Got back home. Shut the engine off. One fan ran for a short period of time.

Lower radiator hose still cold.

Let it cool down. Went out for another 25 miles. Same result.

Other observations:

** I have very little system pressure - just a little psst when I remove the radiator cap immediately after the above drives. Radiator cap is just slightly warm.

** The big upper radiator hose running from the head to the upper radiator connection on the driver's side is quite warm, but it is not hot and I can wrap my hand around it with no discomfort. The smaller hose running from the water pump to the front bottom of the tank is somewhat warm - but not as warm as the larger hose running next to it. The even smaller return line running from the upper bottom of the tank to the small nipple above the upper radiator connection on the driver's side is cold. The engine is running cool and there is nothing to return. And, as I said, the large hose running from the bottom of the radiator on the passenger side to the thermostat housing of the water pump remains cold.

** The aluminum top of the radiator on the driver's side is hot. The aluminum top of the radiator on the passenger's side is cold.

CONCLUSION: This brand new supposedly stock OEM radiator from Lindsey Racing (NOT their billet radiator) is so incredibly efficient that the coolant has cooled completely down by the time it passes from the driver's side to the passenger's side. Either that or this whole rig is magically enchanted.

PLAN: Do nothing further. The temp gauge is right in the middle where it is supposed to be and the engine is nowhere near overheating after an hour's drive. This being so, why should I care whether the lower radiator hose ever warms up?

ALTERNATE PLAN: I will try anything anyone recommends that makes even the slightest sense, because in a perfect world the lower radiator hose would be at least warm, wouldn't it?

Lapkritis

Do you have an infrared thermometer available to you? Harbor Freight sells them cheap. I would confirm temps that way as well if possible.

You could also induce higher temps with much care and at entirely your own risk. In the winter, people accomplish this by blocking the radiator partially or even fully. It's as simple as an old pizza box etc placed in front of the radiator to block air flow when driven. This can be damaging to your engine if you don't pay close attention to temperatures and stop often to monitor until you know how the engine will respond.

Alabama Sam

This is what solved the problem:

Last post I wrote:

** Bought a packet of 8 MM grease Zerks, in order to run a clear hose from the bleeder fitting to the overflow tank (and I installed a new white OEM tank just for this occasion). This is a much more efficient air removal remedy than any other, but I was unable to drill out the Zerk mechanism - its incredibly hard - so I just stuffed the clear hose in the bleeder hole and held it in with my hand and put the other end in the tank. It was very gratifying to watch alternate bursts of air-coolant-air-coolant-air-coolant flow from the bleeder to the tank as I revved the engine, which eventually became nothing but coolant. I don't think there's any air in my system after all that.

Update: Bought a packet of BRASS 8 mm grease Zerks. Easily drilled out the Zerk mechanism. Tried it again. Got more air out. Not a lot, but some.

Extra benefit: The air pockets don't pass over to the tank unless the engine is revving, but when revved you can see the alternate chunks of green coolant and air passing over. This proves the water pump is working.

Problem seemed solved. From cold gauge rises to half (horizontal) or a little higher than that, then declines to the needle just barely touching the lower white mark, indicating the thermostat has opened. Gauge stays there running up to 80 in interstate, drifts a little higher at stoplights in traffic.

This is what proved the problem is solved. Took the advice of Lapkritis and bought a laser infrared thermometer. While the extreme lower part of the lower radiator hose still feels cold, the upper part is warmer. A few minutes after stopping the temps at both ends rise, with the infrared thermometer reflecting 134F at the upper part of the lower radiator hose and 82F at the lower. Ambient 65F. The temp is always going to be lower at the lower part of the lower radiator hose because that where the coolant leaves the radiator after being cooled.

Thanks to all. I'll never be a real mechanic, but with the help of Rennlisters and Clarks Garage I WILL be able to afrord to maintain this car, so many thanks to all.

Next projects: My wipers don't work at all and my instrument lights are too dim.

thomasmryan

Sweet)) can you show us your set up on the bleeder?

It's about 40 here and it stays right below the first hash mark unless I provoke it))lol

The last mile home is slow and uphill...the lower hose gets hot enough to where you could not keep your hand on it....125-130. Some nights the fans come on low speed after shutting it off if it's above 50 outside. An infrared pyrometer is on my wish list.

odonnell

+944 that sounds like a great way to bleed the coolant.

Even in 80F weather, my needle almost never goes over the first hash mark (early temp gauge). The fans kick on about 10 mins into driving, so I know at some point the coolant is 82 deg.C (180 deg.F). I think my thermostat is partially failed and is always somewhat open, or the rest of the cooling system (all new parts wherever I touched it plus 2x 6 blade fans) is doing too good of a job.

Alabama Sam

Better yet, here's a link to the discussion where I found this solution. It has better pics than I can make.

http://www.944online.com/cgi-bin/yab...num=1292014431

william_b_noble

well, to be contrarian "I" changed the thermostat from the top, without removing the radiator, I used a pair of cheap but large harbor freight snap ring pliers. The thermostat had stress fatigued after about 20 years. see photo. I had the exact symptoms (cold lower hose), plenty of heat in the cabin - now car is perfect. hard part was getting the pliers into the snap ring with no visibility