Cloud9...68

The water pump was the first thing I suspected when it started running hot in the summer of 2008, which is why I removed it to test the tightness of the fit of the impeller on the shaft. When I found that it was tight (even after putting it in a large pot of boiling water), I gave it a clean bill of health, and starting looking at other parts of the cooling system. But I'm now suspecting that maybe it was remanufactured incorrectly, so it's back to #1 on my hit list. But I guess I've also been in denial for a long time, given the cost of a new one, and the amount of work it is to replace it. But I'm at the point where I'll do anything, and spend practically any amont of money, to see my temp gauge act like it did when I first bought the car.

jpk

How well do you trust your temp gauge? maybe you're chasing the wrong problem.

Cloud9...68

That's a fair and valid question, and one that I have no way of answering with 100% confidence. All I can say is that the gauge seems to be responding to specific conditions pretty well. When I drive at freeway speeds in 6th gear, when I'm getting a ton of air flow and the engine is under little stress, it indicates a reasonably low reading (about 8:30), and when I do a series of consecutive blasts to the redline in 2nd gear, when the engine is under a lot of stress and there's much less air flow, it climbs quickly to 10 oclock, and then comes down again as I ease off.

Also, the length of time the fans stay on after I turn off the engine tracks with the indication on the gauge.

I plan to buy a digital infrared thermometer this weekend, and measure the temperatures of the inlet and outlet hoses, and see how the temperatures of the hoses (as well as other parts of the engine) track with the gauge. But my gut feeling is that what the gauge is telling me is real. I definitely don't want to go to the track with the gauge acting like it is on the hope that it may be lying to me.

mopar bob

I've seen in years past that some rebuilt have smaller blades and the wrong shape so they don't seal in the housing correctly. As for being tight, that just says that the bushing is still good. If you have a bigger gap or a differnt angle the water can cavitate and that is bad for flow. You may need to bight the bullet and buy a factory one.

Cloud9...68

What you're describing is exactly the type of thing I'm afraid I may have going on with my pump. Just wish there was a way to test the flow before tearing everything apart. I just put in new belts, and set the balance shaft belt tension with a P9210 (not sure if I'm remembering the number right - it's the expensive Porshce tool) I borrowed from someone from another state, so I cringe at taking everything apart again. But at this point, I'll do anything to get this car cooling properly again.

tamathumper

P9201

Cloud9...68

Ah, so I was close. That old dyslexia acting up again...

tamathumper

I hera it's a btihc.

Paul Waterloo

I can use a temperature probe on the outside of my hoses and give you some comparison numbers if you'd like. If I had to bet money right now, if you didn't buy an OEM pump, I would say there is greater than a 50% chance that it's the pump.

I am a long time Audi owner and know first hand how aftermarket parts don't always work right the first time. I have since gone to OEM parts for so many thing....$$$$, but to get it right the first time is worth something to me, plus I do 99% of my own work.

Cloud9...68

Thanks for the offer - that would be very helpful.

And I do agree that it's most likely my pump. The way I like to go about solving problems is to first ask, "When did the change happen," quickly followed by, "What event, if any, happened at the same time as the change?" People have offered all sorts of theories about air/fuel ratios, cam timing, underbody pans, higher internal friction in an engine immediately after a rebuild, etc., all of which certainly can cause an engine to run hotter, but in my case, the one glaring item that stands out is the higher operating temperature soon after the replacement of the water pump.

However, there's a lot of question as to what constitutes "OEM", as Porsche of course doesn't build water pumps, and they've changed suppliers over the years. I believe the current supplier is Laso. Does anyone have any recommendations as to pump brand, and/or ones to stay away from? The variation in price is incredible.

tamathumper

I replaced mine two years ago with a new Laso, and temps remained at 8:00. Then a year later they suddenly rose to 9:00, and then this spring they rose on occasion to 10:00!

Paul Waterloo

Here's a few readings.....drove the car a few hours today....this is after I drove it home and then it sat for a few minutes, then I started it up and idled it in the garage....AC was running. The engine was hot.

Here is where the gauge was:



Here was the engine supply to the radiator....168 F - 169 F, this is my kitchen cooking thermometer, just read the top temperature, the middle one is the "alarm" temperature:





And here is the return from the radiator to the engine....it read 133 F - 134 F:





Ambient temperature was about 83 F with the sun still out in Chicago. Drive your car around and then check these temperatures, if it was a bad water pump and had a lower flow, the supply to the radiator would be hotter, as it would need a larger delta T (difference in temperature) across the radiator to remove the engine heat.

Will be interesting to see what you get.

And just because I want to show off my new car....this is how I got it.....159K miles! The engine compartment is clean!!

Cloud9...68

Thanks very much, and nice car!

I'll buy an IR thermometer tomorrow, and take some readings. Since we're obviously not using the same gauge, the absolute readings may not be meaningful, but the delta between the inlet and outlet hoses should still tell me something. I'll run it until I get as close to the same reading on the gauge as you, and take measurements, then I'll run it hard to get it the gauge to read higher, and repeat the measurements, to see how the relationship between the inlet and output hose temperature changes as a function of operating temperature.

I did check the fan operation tonight, and the low and high speed functions of the fans are working perfectly. I also checked for bubbles in the system, and there are none - nothing but liquid coming out of the bleed screw.

Cloud9...68

OK, here are my readings. I tried to get the engine to a temperature that it would read as close to possible as yours on my gauge:

Attachment 751593

Here are the readings with the IR thermometer I bought today from Harbor Freight:

Outlet hose from cylinder head = 178.5 degrees F
Fat lower return hose from radiator = 148.5 degrees

According to some info provided by Tamathumper, the reading on the gauge where our cars' needles were pointing during our tests is about 185 degrees F, so my measurement indicates my gauge is accurate to within a few degrees. The ambient temperature was quite a bit hotter here than where your did your test - right at an even 100 degrees. So, both of my readings were about 10 degrees warmer than yours, but a good chunk of that is probably due to the differences in our gauges, and the different ambient temperature.

I drove the car extremely hard today at the hottest time of day, taking it to redline repeatedly probably 30-40 times, trying to see if I could get it to overheat, but I was never able to get the gauge to read above about a needle width below the 10 o'clock line. It seemed to be noticeably cooler than it was when I drove it hard this past Monday, but I can think of three possible reasons for this:

1. It was about 4 degrees hotter on Monday
2. I have heard that an engine will run hotter until it is fully broken in. My engine has just been rebuilt, and I literally just started driving it hard this past Monday. All this running to the redline has probably gone a long way to seating the rings by now. If fact, I noticed that it seemed to feel stronger and stronger as the runs progressed today. This is car really fast - hard to believe it's an NA motor.
3. The car sat for 2.5 years during the track car conversion project with old gas, which we know loses octane as it ages. I've filled it up with fresh gas, but I'm sure that until recently (maybe until today), there were still remnants of the old gas in the system. The ECU will retard the timing if with lower octane gas, which will make the engine run hotter.

So, I'm not at all convinced I have a cooling problem after all. I'll keep an eye on things, get my hands on some belly pans, and probably go ahead and swap out the cheapie remanufactured water pump I installed in 2008 with a new one, but I don't think there's any reason to keep this car off the track.

Paul Waterloo

I didn't realize the other facts that you reported....and in the end, your delta T across the radiator was measured at 33 F, mine is 35 F, so for the same given radiator, it appears we have about the same flow across it. The higher the delta T across the radiator, the longer the coolant is spending in the radiator, the larger the delta T.

I would just drive it for now.

I sent you a PM here on the "batwing".