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Thread: Is it water pump time?

  1. #1
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    Is it water pump time?

    History: bought my 98 328is in 2007 with 109k
    Within the 1st year I replaced the water pump, thermostat and housing. I put in a Graf, metal impeller pump, an 82° thermostat and an aluminum housing. Including the 88° I put in today I've changed it 3 times. The one I took out was a stock 92° but my temps have been running in the 100° range. I've only put 40 k on the car in the last 11 years so my question is, is it time for a new pump? Once it gets up to temp it stays there, turning on the AC and aux fan doesn't change anything, turning the heat on high will bring it down a few degrees. I have no leaks or air in the system. Right now with the 88° its showing 95° or just over 200°F. Sugestions?
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    Gave away my BMWs, driving a VW and an Audi now.

  2. #2
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    T-stat temp just sets the floor for how cool your operating temp can be. Doesn't really do much for the ceiling. So when it's hot out your car likely will get to the same temperate regardless of what t-stat. Considering you can put extra load on the engine with no negative affect sounds like you're fine.

    Sent from the dark side of the Moon

  3. #3
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    As Nanniepoo states, you seem fine as there are no excessive temps.

    As long as your temp gauge is prevented from creeping into the red,
    the radiator AND shrouding seem to be in good condition-no leaks,missing pieces,
    and you perform fresh coolant replacement as part of preventive maintenance,
    the cooling should be fine.

    Btw, proper oil condition and circulation have a lot to do with proper engine cooling,
    a little known fact, or maybe just ignored.
    You do perform recommended fluid and filter changes-coolant & oil?

  4. #4
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    Btw, proper oil condition and circulation have a lot to do with proper engine cooling,
    a little known fact, or maybe just ignored.
    You do perform recommended fluid and filter changes-coolant & oil?
    I keep on top of fluid changes, the oil is over a year old but the mileage is very low and the onboard indicator still shows Al the green bars. I don't use that indicator as an oil change guide. I doubt I've ever gone over 3K on a change and have used synthetic or synthetic blend for every service. It's just that the gauge used to run real close to the temp of the thermostat. I may just spring for a new pump, its cheap insurance and not a major project.

    Gave away my BMWs, driving a VW and an Audi now.

  5. #5
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    Are you using two temperature sensors? I assume the digital one gets its info from the DME (which gets it from the stock sensor) and the analog one from another sensor.
    So that would with 99.99% certainty exclude the possibility that the sensor is bad..

    I personally think the thermostat is the more likely culprit. It probably opens and closes fine, but has not been calibrated correctly at the factory and seems to open at 95 degrees C.. If it degrades further and the temp at which it opens gets higher and higher you might/will eventually run into trouble. I would personally change it.. My 92 deg C thermostat seems to open at exactly that temperature, and every time I double check with INPA it's at or very close to that temperature..

    If you turn off the A/C, and hard-wire the high speed fan (easiest to take off the temp switch connector at the radiator and make a ground connection to the pins until the high speed fan turns on), the temp should definitely drop to 88 degrees C with a correctly functioning thermostat. Unless the outside temperatures are really high. Best to test in the early morning when the ambient temps are low.

    The cabin heater functions without interference from the thermostat.. So the fact that such a small (cabin heater) radiator CAN cool the engine down, means that the most probable cause is the thermostat.

    In itself 95 deg C shouldn't present direct trouble, as it's only 3 degrees above stock (at least my European 323i M52 stock temp), but I would worry about the thermostat degrading further.. I would change it whenever you have time and/or you wanted to replace the coolant anyway.. Until that time, keep an eye on the temps.. Probably nothing bad will happen..

    Water pump would show problems under load.. If the temps stay stable under load, then I wouldn't suspect the pump.. I'd suspect the thermostat. Or, perhaps, the temp switch in the radiator? If it only turns on the aux fan at 95 deg C, then the engine would never run any cooler than that in stop and go traffic.. But on the highway it should drop to the thermostat temp. So, again, my guess is that the thermostat isn't calibrated correctly at the factory (or perhaps swapped part numbers?)

    Good luck!
    Last edited by ed323i; 06-27-2018 at 06:41 PM.


    1997 E36 BMW 323i
    (European) 275k km (171k miles), with following small mods:

  6. #6
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    No mention of radiator condition. If it's original and the car sits as much as described in the OP it could be partially restricted. Sediment settles to the bottom and reduces cooling capacity. Just a thought.

  7. #7
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    Is the Graf pump a cast aluminum or welded-SS sheet impeller?
    In my opinion some efficiency is lost with cast aluminum impeller, I prefer a Saleri (with composite impeller) or Hepu …ah I see current Graf is welded-SS.
    Next I’d look at mechanical WP driven fan clutch, can you stop the fan turning w/rolled up news paper, replace the fan clutch if so.

    As for you oil change intervals, oil should be changed annually even if low miles. Oil ‘oxidizes’ after bottle has been opened.


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  8. #8
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    The radiator is not original, the date on it is from 2002 so it's still old. The analog sender is mounted in the coolant line for the throttle body, but the temps are very close. My thoughts are its a flow issue.

    Gave away my BMWs, driving a VW and an Audi now.

  9. #9
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    OK, so temp sensors/senders must be good.

    I'd do the test: When it's relatively cool outside, take a drive until car is at operating temperature (95C in your case). Then park it, hard-wire the high speed fan, turn off the A/C.
    If temps stay at 95C, at idle, A/C off, high speed aux fan on, it should be the thermostat. Double check by carefully feeling the temp of the radiator. With high speed fan continuously on, it should drop quite quickly and should eventually feel warm or even relatively cold, and shouldn't be hot at all (shouldn't hurt your hand)
    If temps stay at 95C, even while driving at the highway, it should be the thermostat. It excludes the temp switch or the viscous clutch as being the cause.
    If temps stay at 95C, even while climbing large hills at high loads (accelerating for as long as possible), then it can't be the pump or flow issues or bad radiator. It must be the thermostat.
    If temps do drop when you turn on the heater, which blows air through a radiator that's much smaller than the front radiator, then it's probably the thermostat.

    If all four check out, then I really, really think it's the thermostat.. You're probably just in bad luck. The old thermostat failed and you replaced it by one that has been calibrated badly in the factory (or it received the wrong part number).. You could take it out and test it in heated up water, using a thermometer to see if it's calibrated correctly at 88 deg C.

    P.S. You can also hard-wire the high speed fan by taking out the high speed aux fan relay and bridging it directly.. But it's safer to do it with the connector of the temp switch in the radiator. I used a needle to insert a thin cable into the connector/plug and connected the cable to one of the three bolts on the shock tower. It's completely safe as it only supplies ground to the relay. You can't cause a short. Just try all three pins and one of them will trigger the high speed fan (when ignition is on).. You can also connect between two pins on the connector, as one pin (I believe the center one) supplies ground.. Also here: no risk of shorts or whatsoever. In the fuse/relay box though, making the bridge there, can cause major trouble if you connect the wrong pins, so best to do it at the radiator side.
    Last edited by ed323i; 06-27-2018 at 08:23 PM.


    1997 E36 BMW 323i
    (European) 275k km (171k miles), with following small mods:

  10. #10
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    If you are lucky enough to have an old school radiator shop in the area they can flow test it. If not you can do it yourself with an easy home test. I learned this from a man at my local shop who was in the biz for 50 years. Remove upper and lower hoses. Block the lower hose port with your hand. Have a helper fill the radiator through the upper hose port with a garden hose until is runs out the port. Remove your hand from the bottom and watch the water. A clear radiator core will run like a fire hose. If you get a slow flow then the bottom of the core is stopped up. It's easier with the radiator out but not necessary.

  11. #11
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    Quote Originally Posted by jmo69 View Post
    The radiator is not original, the date on it is from 2002 so it's still old. The analog sender is mounted in the coolant line for the throttle body, but the temps are very close. My thoughts are its a flow issue.
    You could look at a high flow Stewart WP, awesome, but my experience is that it does not last longer than a stock pump.


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  12. #12
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    Quote Originally Posted by bluptgm3 View Post
    You could look at a high flow Stewart WP, awesome, but my experience is that it does not last longer than a stock pump.


    Sent from my iPhone using Tapatalk
    I got 10 years out of this Graf pump if it has failed. Believe it or not I've still got the one that was in the car when I bought it. It seems to be in good shape yet. I've also got the one from my m54b25 that would fit, but that one feels different. When I turn it by hand the shaft and impeller turn together in both directions but when I change direction they will turn 10 or 20 degrees and then feel like they hit something. Almost like play in the bearing. I may try the original pump and if the temps come down I'll know it's the problem. I didn't want to change both today and not know the which one was the fix if the issue was corrected. I really don't feel comfortable messing with the wiring for the electric fan.

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  13. #13
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    In my opinion some efficiency is lost with cast aluminum impeller, I prefer a Saleri (with composite impeller) or Hepu …ah I see current Graf is welded-SS.
    Next I’d look at mechanical WP driven fan clutch, can you stop the fan turning w/rolled up news paper, replace the fan clutch if so.

    As for you oil change intervals, oil should be changed annually even if low miles. Oil ‘oxidizes’ after bottle has been opened.
    I have a cast aluminum impeller pump in my m54 and that car holds its temp at 93° C with no problem. I'll test the fan clutch tomorrow after a few highway miles and next week I'll do an oil change.

    I still might put the old Genuine pump back in just as a test.
    Last edited by jmo69; 06-27-2018 at 11:38 PM.

    Gave away my BMWs, driving a VW and an Audi now.

  14. #14
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    I can't understand the problem, maybe I'm dumb. For a start 100°C is the nominal temp the engine will operate at and it's not a problem until way over 130°C. Engine oil wants to work best at around 100°C.

    Are you concerned that the temps that you measure are different to that of the thermostat threshold? Because those two numbers are rarely the same.

    Exactly where are you measuring the coolant temp? Based on your description there is no problem so I certainly wouldn't be buying new parts or dumping coolant to change parts...
    '96 M3, S50B32, 6MT
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  15. #15
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    I have an 88 C thermostat, Stewart pump and all new cooling system parts. My Autometer gauge in the cylinder head holds steady at just about 200F. That temperature is great. Keep in mind the thermostat starts opening at the rated temperature and opens more as the temp gets higher so it just barely starts flowing at 88C/190F and the water temp will be slightly higher when operating. If it doesn't heat up more while loading the engine I think you are chasing a problem that doesn't exist.
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  16. #16
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    Quote Originally Posted by jc43089 View Post
    I have an 88 C thermostat, Stewart pump and all new cooling system parts. My Autometer gauge in the cylinder head holds steady at just about 200F. That temperature is great. Keep in mind the thermostat starts opening at the rated temperature and opens more as the temp gets higher so it just barely starts flowing at 88C/190F and the water temp will be slightly higher when operating. If it doesn't heat up more while loading the engine I think you are chasing a problem that doesn't exist.
    +1

    I must admit I can't get my INPA to run with the engine on.. It gives connection errors (probably due to interference from all the electronics, coils firing etc, so need better shielded USB adapter cable probably).. I wrote I tested the temps a few times and it was always at the thermostat temp, but those tests were performed a few minutes after shutting down the engine after driving around for some time, mostly in hot weather (turn off engine, open hood, connect usb adapter, turn on laptop, run INPA, so a few minutes).. It would always show 89 degrees or 91 degrees C or something in that ball park. So, in my case, it seems temps are quite near the thermostat rated temperature, but in general, like others wrote it should be a little higher.. So, in your case, it seems there is no problem at all.

    If the temperature remains stable at high load (do the hill climb and highway test, accelerating as much as possible, or perhaps curvy roads, accelerating, braking, accelerating braking) then it just can't be the water pump or the radiator or a flow issue in general. Replacing the water pump will be a waste of money, time/effort and coolant. Under high load, if there is a flow issue, then the temp should increase significantly.

    If you're uncomfortable with the operating temperature then you can just install a lower temperature thermostat.. Assuming what JC43089 wrote is correct, take a thermostat with a +/- 5 degrees C lower rating than what you want the operating temperature to be. So, if you want it to be 88C, then get a thermostat that's rated at +/- 83C (I think there is a 80 or 82C one). But you also need to look at the temp switch in the radiator and/or clutch fan if you want it to run at lower temperatures. If you still have the original aux temp switch in the radiator, it will only turn on at 92C.. So, it would be impossible to get the engine to operate at anything lower than 92C, unless your viscous fan is in great condition or you're at the highway (enough air going forced through radiator).
    Last edited by ed323i; 06-28-2018 at 11:09 AM.


    1997 E36 BMW 323i
    (European) 275k km (171k miles), with following small mods:

  17. #17
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    I just made a short, 6 miles, run on the highway at 70 mph with the AC on. The temp on the app was 204 with a jump to 206 when I got to the bottom of the off ramp. The gauge that's reading coolant temp in the throttle body hose less than a foot from the head was showing just above 200. So the readings do seem to be accurate. I used a rolled up shipping envelope to test the fan clutch and was able to stop the fan pretty easily so I'm guessing I should get a new one.

    Gave away my BMWs, driving a VW and an Audi now.

  18. #18
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    Seems promising.. Not a very long test, but if the water pump really was bad, then it should have shown.
    Getting off the high way, and driving slowly or at idle, after driving 70 mph, means that after a relatively high load (during which there was enough air moving through the radiator), and some heat accumulated in the head you instantly loose a lot of cooling when the viscous fan isn't working properly.. The small rise in temp is then to be expected. If you'd keep the car idling after that, you'd probably see it creep up a little more, or worse, a lot more.

    So, best to replace the viscous coupling and/or do the fan delete mod. I personally really like the FDM, but opinions differ ;-) .
    In my case, just installing the 80C/88C temperature switch in the radiator and keeping everything else stock seems to be a winner. Summer is starting now, so will keep on checking, but it seems promising.
    As you already have the digital and analog temp. readouts you can safely experiment with the fan delete mod. If you also add the water-wetter, I think you can be quite sure to have a stable solution.
    Some people also install the lower temp. thermostat, but I don't think that's necessary in most cases (haven't really looked up the climate data in Wisconsin, so perhaps someone can correct me here)..

    Best to at least change the viscous coupling of the fan, and/or install the low-temp temperature switch in the radiator. The aux fan can do quite a lot of efficient cooling, especially with the A/C off. Then do some more, and longer high load tests. If the coolant temp remains stable, then you can be sure it's not a flow issue.
    Last edited by ed323i; 06-28-2018 at 04:59 PM.


    1997 E36 BMW 323i
    (European) 275k km (171k miles), with following small mods:

  19. #19
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    A few years back I removed the mechanical fan and during that time took a 700 mile road trip. It was summer but not extremely hot and with either the 80° or 92°(cant remember) thermostat the gauge only crept up close to 200 once while waiting to get through customs at the Canadian border. Otherwise it was good the rest of the time.

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  20. #20
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    I did what ed323i did, removed the mechanical fan, kept the stock thermostat and used a lower temp aux fan switch, works a treat.

    Keep in mind that I also have an oil cooler though so that helps also.
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  21. #21
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    Mine was running really hot and I changed my thermostat and dropped it 30 degrees F. I honestly thought I had a radiator issue the way it acted but it was just a faulty thermostat.
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  22. #22
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    The thermostat is basically a flow control valve, adjusting flow based on temperature,
    now if there are unknown obstructions causing oppositions to flow in the system,
    then those must be found and eliminated.
    I would definitely replace that fan clutch, as after that test,
    it is defective.

  23. #23
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    I think my first step will be to see how well the radiator flows, maybe try to back flush it. Something definitely isn't right. I took my e46 on a 200 mile trip this weekend with temps in the mid 90's and the app gauge never went over 204°, most of the time it was under 200°. The AC was on full and it was having a hard time keeping up.

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  24. #24
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    Your E46 has an electrical fan, which seems to function perfectly.
    The E36 has the mechanical fan, which very probably isn't working well.. And the aux fan will only turn on very late with the original temp switch..

    I would first replace the mechanical fan, or do a proper fan delete mod (at least the 80/88 deg. C temperature switch).. Then test again. And go from there.

    On the other hand checking the 10+ year old radiator isn't bad of course, but I doubt there is any problem there. Otherwise it would have shown on the highway.. There is nothing wrong with 204 degrees F (95 degrees C). But with the bad mechanical fan (and the aux fan starting way too late) it will rise when you're idling or in stop-go traffic.


    1997 E36 BMW 323i
    (European) 275k km (171k miles), with following small mods:

  25. #25
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    Torque is going to be reading the temperature in the engine head so it's going to be somewhat higher. I have an 88C thermostat as well and my normal operating temp is between 205 and 215F, hot day or cold doesn't matter.

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