Water Pump and Thermostat
 

At some point in my future a new Water Pump and low temp thermostat is in my future now that I am almost 70K miles

My question is why are some water pumps advertised for $400 with composite impellers and there are some with metal impellers for 90 bucks ??

I could understand a 15% difference in price but not 300%

That's easy: You will replace the metal impeller units several times before you replace the OEM pump once. Metal impeller pumps also can be devastating to the engine cases when they start to wobble with wear. Do a search, been covered several times.

OK , Thanks ...in the BMW world ( I reside there also) the Metal Impeller pumps are what everyone uses to replace then the OEM units grenade...and they do often.

Ok
 

Are these Junk ???

Porsche Boxster 97 04 911 99 05 Water Pump w Impeller USA | eBay

If they weren't im pretty sure a lot more folks would be using them. My advice is to use an oem pump. Dont necessarily need the Porsche pump, go to pelican and get the kit with the low temp thermostat for 330 bucks. Youll have peace of mind knowing youve got a quality part keeping your investment from melting. Im not sure the water pump is a place you want to compromise.

Hi.new here.just got my boxster 2000 25cdays ago i think the water pump is gon.going to try to replace my self.i di check the overflow tank, and is ok.after i park the car for couple minits i was able to see the dripping under the car just berrind the passenger seat.any one can help me with a link to show the best way.tks alot.

Many resellers discount the OEM Porsche water pumps. Here's one for $285. 2000 Porsche Boxster Roadster H6 2.7L Engine Cooling Water Pump - 99610601156 - Water Pump - ES#2224253

Do not install any water pump with a metal impeller.

http://986forum.com/forums/uploads01...1407783990.jpg

I would also seriously consider not using anything but OEM.

Get it from Sonnen, Sunset or Suncoast.

I once bought 6 ebay water pumps. Installed 2 in two cars at same time,
first one failed at 1K miles, second one did not actually fail - but I proactively removed it and it already had play in the shaft at about 300 miles.

I threw the other 4 in the garbage.

Frankly it's not worth the $100-$200 to play roulette. The OEMs aren't great,
but they seem to last ~30k miles.

I did read where someone was looking to put a wire mesh as part of the gasket --
this could catch impeller debris if it wasn't too small -- but I don't know if that
was just internet speak -- or whether the poster actually did it.

YMMV, but I only use OEM now.

Mike

Forgive my ignorance but what are the benefits of a low temp thermostat?

From what I understand
 

I have work on many different types of cars but this is my first Porsche, the low temp Tstat is completely open at 160 degrees and simply lets your engine run cooler. Cooler is always better on engines and the factory one opens partially at 185 deg...if I read this right.

The engine will NEVER run cooler than it currently runs. The Tstat does nothing to cool the car. It simply opens earlier. Nothing more.

Pierburg only for the water pumps. Gamble with the rest of the crap out there. See a good price on a water pump? Call and specifically ASK "what kind is it" If they cannot tell you? Then buy it from another source. DO NOT ask for the Pierburg. Ask them what they sell.

I'm fortunate enough to be 30min from the only authorized water pump rebuilder Porsche has in the USA. I've seen ALL the failures. ALL of them. Porsche actually comes to him 2-3 times throughout the year to go over the latest issues.

Not a bad price at all
 

Looks like they can be had for under $250

Porsche Water Pump - Pierburg 99610601156 | FCP Euro

this is the first search I did. I will go this route when I do mine. Brad you are certainly a big help for us novices.

Thanks
Dwight

Why fit one then?

If you want a very good explanation about low temp thermostats from an acknowledged expert do a search on the 911uk forum for LTT or bazhart.

Braszucca, lift the mat under the coolant tank. Is it perfectly dry down there? Check the cap. The overflow hose runs down where you are describing.
Re: the low temp thermostat, I put one in and have noticed absolutely no difference in running temperature.

low temp thermostat
 

Well FWIW Brad is right, I was not thinking....I did this to my E36 years ago when I replaced the radiator and water pump and it runs in the same place...but I do have a little better peace of mind.

Sorry, but that is not correct. Yes the thermostat opens sooner, but in doing so changes the steady state operating temperature because the function of the stat is to set the minimum operating temperature.

It has been repeated documented by our shop and others that the steady state temp drops significantly, as does the oil temperature (often by 25F).

NO argument :)

Show me. Show me the test case, test scenario. I have 4-5 years of AIM and Motec data logs showing ZERO decrease in water temp. My logs are 25-30min logs and multiple 3-4 hr logs. With and without 3rd radiator, with and without BoxsterS water lines. With and without standard coolant (with/without water wetter)

I *know* you know better than to read the gauge for this. Show me :cheers:


We are racing. I have steady state consistent lap times in all sorts of different weather. I'm suspecting what your seeing only pertains to certain circumstances.

The only time the low temp tstat would lower temps of the engine is when you are cruising on the highway and there is much more cooling capacity (because of a low ambient outside temp) than there is engine heat being transferred into the coolant. The tstat would stay open lower than the normal 186 and allow the engine to 'feel' the cooler coolant temps, probably stabilizing around 167, 169.

As soon as the engine starts putting out more heat than some specific amount (which isnt hard to do, in 90F weather my temps go up to 200 even at 70MPH), the lower degree tstat will just dampen the heat up cycle because of the coolant flowing around earlier in the heat up cycle.

City driving, hot weather driving, idling in traffic etc will all still produce the same steady state temperature, because the low temp tstat only allows wiggle room in the scenario that I described.

For someone that says "No argument", you definitely come across as someone spoiling for one.

That said, I would fully expect that a 160F stat is not going to do much for a car being flogged on a track. First of all, racing is never "steady state"; on the track, everything is changing all the time (air temp, RPM range the engine is seeing, the number of cars holding you up at any given moment, load on the engine etc.), which only adds to the confusion when trying to reproduce results; and the thermal load conditions that car is seeing is totally different than that of a what street car sees. And as my comments are directed at street use, which is where the low temp stat was designed for, they do not apply to a car used in track applications.

On several customer's 986 (we done this with both base and S cars, Tips and manuals), fully instrumented (read not using the factory displays) when equipped with the OEM stat and running at a steady prolonged speed (target speed of 40-50MPH) with an ambient temperature in the 68-72F range, we have tracked coolant and oil temps over extended driving periods. Nominal coolant temps tended to be in the 210-215F range under these conditions, with the oil running 20-30 degrees or so warmer. With no other modifications, the same cars produced steady state coolant temps of 175-180F by switching to the 160F stat, with a concomitant drop in the oil temps as well.

Will the street driven car heat up and turn the fans on if it gets stuck in traffic? Yes it will, but it will take it longer to do so, and will cool back down to the lower observed steady state temperatures once air flow over the radiators comes back and the car returns to cruising speeds.

So does using a 160F thermostat result in lower coolant (and oil) temps on a 986 driven on the street? Most definitely. We have also tracked UOA's on some street cars, before and after they were switched to the 160 stat, and observed slower oil degradation over time, which is probably attributable to the oil seeing consistently lower temperatures as well.

So both are right under different scenarios?

Reading you both...

The low-temp isn't going to let more coolant through to the radiator (just sooner) but in the low speed running low thermal-loaded state the temps will be lower thus when the engine needs more cooling the radiator coolant starts out from a lower base.

Raise the temps toward or to the thermal max of the radiator (as in racing or A/C on on a hot day) and the low-temp thermostat will have no effect as the same coolant flow will get to the radiator and the radiator will cool to its max (if the leaves have been cleaned out).

It will take a while for the coolant to return to lower temps (because that only happens when the radiator can remove more heat than the engine is producing) even at low thermal-load road speeds but the low-temp thermostat will allow eventual return to a lower state.

On a road car, the oil will last longer because it spends more time at a lower temp.

So I'm left with the questions:

What is the real coolant temp difference between running at a constant 40-50 MPH and 70?

Once you raise the temps to the max the radiator can handle, how long at a moderate speed does it take for the temps to drop to the point where the low-temp thermostat makes a difference?

How much does the ambient temp influence the max cooling capacity of the radiator? IOW, how hot does it have to be out on a road car (because most of ours are) before the low-temp makes no difference after warm-up?

Interesting
 

and quite a bit of good information here to be had...many thaks guys.

So what is really happening is the Bell Curve of the operating temperature will just be different with the lower T Stat due to it opening sooner....been a long time since statistics.

This is turning out to be a great thread!
So...if we weren't interested in the heater ever working, why not get rid of the T- stat all together? What do race cars need them for?
I think I know the answer, but I want to hear from the experts.

Mike, the difference between 40-50 and 70MPH is not substantial in terms of the "steady state temperature of the coolant, but the rate of change (how quickly the car will cool from the heavy traffic temps) when coming out of traffic onto an open road is higher for the car going 70 due to increased air flow over the radiators.

At an ambient temp range of 68-72F, it will take a few miles for the engine to shed excess heat with either stat, but what does happen is that as you approach the nominal "steady state" temp of either stat, the thermostat begins to throttle the coolant flow a bit, so the rate of change gradually slows and begins to cycle up and down slightly until is settles at the nominal steady state temp. Because the available heat transfer rate is basically constant (limited by the radiators and air flow), the OEM stat will reach its steady state temp sooner than the 160F stat will as it does not have to shed as much heat.

Ambient temps do have a significant impact on cool off rates; a car running in 40F air will cool much quicker than one in 80F air. But in either case, again at steady state, the car with the 160F stat will be running much cooler than the OEM stat; the only thing that really changes is the delta or rate of temperature change attributable to the difference in air temps.

You can actually flow too much coolant at higher RPM's, and when moving too quickly past the radiators, will not have time to shed enough heat. A lot of racers replace the thermostat with a thin metal disc with holes drilled in it to control the flow rate without any chance of the unit failing as a thermostat can do at the most inopportune moment. Trick with using the metal plate is to find out how many of what sized holes are "just right" for your car with a given track and air temp. Going this route will also drastically slow the engine warm up time, particularly as the air temps drop.

Thanks JFP.....very informative to DYI'er like us....THANKS !!!

I agree with all of this, I think we were all saying the same, mostly correct things, just talking about different sides of the argument.

Now the thing I am curious about is: running oil at a cooler temp (to a point) is a good thing, no contest. But running the coolant COOLER than what the ECU is expecting as a 'warmed up' engine could also be bad. Fuel trims are different based on engine temperature, and the tstat being a 180 degree tstat is that way so that the M96 can run at the CORRECT heat based on its sensors and fuel map, metal composition, expansion factors, tolerances, etc...right?? Seems like running at a lower temp (to a point as well) could also be bad, in the best case, potentially just worse fuel economy?

Has not proven to be the case with a 160F stat. The DME has the leeway to adjust the fuel trims from cold start (often very cold) to running in Death Valley conditions., as well as adjusting for pretty large changes in altitude. If the DME ever "ran out of rope", the car would start coding because the computer had reached its limits; I have never seen or even heard of that occurring with a low temperature thermostat. You need to also not that the "high output" Porsches (Turbos, GT cars) run 160F stats from the factory.

I've also not hear of anyone suffering decreased MPG as the result of using one of these units; and in fact have had customers comment that they feel they are seeing a small but reproducible increase in fuel mileage. I don't really know how real that is, but after several different customers commented on it, you have to take note of it.

I didn't mean that the DME would run out of rope, I realize it has the ability to adjust fuel trims to many temperatures and altitudes. What I meant was that it would stay in some 'almost-warmed-up-fuel-trim state' by allowing the engine to cool to around 160 when on the freeway in low load conditions etc....because the DME expects 180 (186) minimum to be the steady 'warmed up' state on our cars.

Unless of course the DME doesn't think 186 is warmed up, but rather something lower. It depends on the fuel map vs. coolant temp. In a graph of those two, there is some temperature when the DME stops considering the car 'warming up' and changes its fuel trims accordingly. It very well could be below 160, in which case running the 160 thermostat would help in some circumstances to lower the coolant temp.

Which makes me think...why fit a 180 tstat at all? If running lower than 180 is better in some cases and doesn't affect the engine warmup fuel trims, why even put a tstat in the car from the factory that makes it run hotter? Also, why let the car heat up to 212 before turning on the fans?

I'm pretty sure it has to do with emission testing.

I could be wrong -- but thats my best guess.

Mike

Thats a good point, getting the engine up to temp faster would reduce emissions

Mike is correct, it is done purposely for emissions. The quicker the car gets hot, and heats up the cats, the faster it falls into the emission "zone".

Interestingly, we ran a couple side by side scold start essions on the rollers with sniffers in the exhaust, and saw very little difference between a car with the OEM stat and the lower temp unit, other than it took a couple extra seconds to line out at the same final values.

In most cars a "low temp" thermostat is a bad idea. But in the water cooled Porsche engine, the thermostat is put in an oddball location. Most cars put the thermostat in the EXIT port where the hot coolant leaves the engine going off to the radiators. In the Porsche engine, the thermostat is put in the INTAKE port where the (cooled off) coolant returns from the radiators and enters the engine. Perhaps this is why the low temp thermostat is helpful.

I've never figured out why the Germans put the thermostat in that location. IIRC my VW Scirocco and Jetta did the same thing Porsche did. The Americans, British, and Japanese all put the thermostat in the output port, so that hot water goes off to the radiator.

Whats your results from using water wetter? I've always wanted to try that stuff, but that was around the same time I experimented with marvel mystery oil :eek:

Water wetter, or what ever brand name you choose, is just a surfactant mix to lower the surface tension of water. If you are using a water/coolant mix, it is unnecessary as the coolant already carries similar capabilities, and not all of the commercial products maybe compatible with Porsche coolants.

IIUC you aren't allowed to use antifreeze on most race courses - it would make the track slippery if spilled all over after a crash. So you can use water wetter with distilled water for coolant there. That wouldn't create a hazard.