Overheating & blowing cold from heaters. Is it definitely the water pump?

[Chasabi]

Yesterday I managed to bump the front of my beloved Zed. A Mondeo had a huge tow bar that was sticking right into the parking space that I pulled into. I didn't see the bloody thing and I hit it. It didn't cause any visible damage, just left a black scuff on my number plate.

I left the supermarket and went back to work. A few hours later after work I jumped in the car to drive home. After about 10 minutes I noticed that fan had kicked in. Another 5 minutes later the temperature gauge was heading for the red zone And it eventually beeped and lit up red so I pulled over to let it cool down. After about 10 minutes I set off again. I don't have breakdown cover and I was on a tiny lay-by on the M62 in rush hour traffic, I didn't feel safe. 5 minutes later the temp gauge hit red and the car went into limp mode. I drove the last 10 miles home at 30 MPH in rush hour on the M62. I pissed off a lot of motorists!!

Once home, I let the car cool down before checking the coolant level. Almost empty, maybe totally empty! I topped it up with some decent coolant and fired her up for a bit. A friend who is a mechanic told me to run it with the heaters on full and to unscrew the little bleed valve on the pipe near the coolant filler cap. I did this for 10 minutes and the temp gauge stayed dead in the middle. I put the coolant cap back on, tightened the bleed screw and let it run for 5 more minutes. The temp gauge still didn't move from the middle so I went for a drive. 5 minutes later the temp gauge started heading for the red zone so I turned round and got back on the drive before it hit red. I also noticed that the heaters were blowing luke warm even though the car had been running for a good 15 minutes. They are usually blowing red hot after 15 minutes.

I've just checked my coolant level now and it is low, maybe almost empty. There's a damp patch under the car too so there's definitely a leak somewhere. Could a leak cause these symptoms? From what I have read this sounds like a faulty water pump although I'm crossing my fingers that it is something else because I don't fancy shelling out £500 for a new water pump plus fitting.

I'm also wondering if I could have caused any damage by driving it that last 10 miles in limp mode? It seems to start and idle fine. I hope I've not fried the engine.

Is it just a coincidence that I bumped the front end too or could that have knocked something loose? I can't visibly see anything loose nor can I see coolant dripping from anywhere.

 

[Chasabi]

BTW I've got an OBDII Bluetooth devices which I have connected to the ECU and scanned for error codes. It cannot find any error codes. I know this works because my Dad's Ford Focus had an engine warning light and I was able to see the error code on my phone using this OBDII device. The zed hasn't come up with any warning light which is strange for such an expensive and advanced machine. I would've thought that the ECU would know that something isn't right!

I'm also concerned that I saw no coolant level warning. Does the Z4 have a sensor for the coolant level?

 

[Smartbear]

Hi, I'd be amazed if the pump is damaged from your parking incident, the rad is a fair way back from the grill so would be surprised if that suffered impact damage equally.
You need to find out where the leak is coming from as that's obviously the issue here, stop driving it until you've done this or you will need a replacement engine if it's not damaged already
Rob

 

[cj10jeeper]

Leak in the cooling system, highly unlikely to be the water pump as asked in your post title.
Blowing cold air is because you have no coolant. As above stop driving it else you'll wreck the engine, find the leak, top it up, purge any air and you'll be good to go.

Again probably not the bump if as minor as you indicate, but leak could be anything from a crack in the radiator, hose clip loose, hose split, etc. I'd have the rad cover off under the bonnet, engine off of course and start feeling around for the source of the leak

 

[Chasabi]

Thanks for the reply guys. I'm hoping it isn't the water pump

I did see something online about bleeding the system. I had a look earlier today and I was going to top up the coolant and give it a try. It looks completely empty, the float is as far down as it can go, but when I remove this little plug, the coolant level shot right back up to the top. What does this indicate?

So at the moment it appears that the coolant is at the maximum level. It's strange

 

[Smartbear]

I think this is incidental, the most important thing is to find the source of the coolant leak & fix it, worry about bleeding it after you've done this
Rob

 

[mr wilks]

I think this is incidental, the most important thing is to find the source of the coolant leak & fix it, worry about bleeding it after you've done this
Rob

& don't drive it even at low speed if the gauge is off the scale , these engines do not like heat & are easily ferked

 

[Chasabi]

I've had a friend round to look at it for the past hour and half. He's a mechanic and I trust is judgement. He tried everything possible to find a leak and bleed the system but it wasn't having it. The pipes from the expansion tank that feed the heater just would not get warm but the water in the expansion tank was steaming hot once that car had go up to temperature. It was as if the water isn't being pumped round correctly, hence the diagnosis that the water pump is toast He's going to get me a price tomorrow.

Does that sound about right? Should I replace the thermostat too?

 

[Smartbear]

I can't see how the pumps been damaged from a slight scuff on your number plate, it doesn't seem likely?
Rob.

 

[Anonymous]

I can't see how the pumps been damaged from a slight scuff on your number plate, it doesn't seem likely?
Rob.

^^^^^ this

It's very unlikely ( not impossible I guess ) that you have sustained pump damage from the bump . However , if you have cause a leak from damaged pipe work or radiator cracks then having driven the car to the point where it goes into limp mode , maybe the cooling system running dry and causing pump failure . Not what you want to hear, but sounds like a possibility .

As others have said , find the cause of the problem ( leak in cooling system ) before investing in any replacement parts . Fix the cause before fixing any casualties of the cause .

 

[markplant]

To the people that know more about this stuff than me, so most of you.
Is the thermostat just mechanical an opens an closes or does it have any wiring that might in turn tell the pump to run,
Would it be worth looking for a lose connection

 

[srhutch]

To the people that know more about this stuff than me, so most of you.
Is the thermostat just mechanical an opens an closes or does it have any wiring that might in turn tell the pump to run,
Would it be worth looking for a lose connection

Facelift models have alectrically assisted thermostats, not sure if the link to the electric water pump in any way though.

Could the Thermostat could be stick shut though?

 

[Anonymous]

To the people that know more about this stuff than me, so most of you.
Is the thermostat just mechanical an opens an closes or does it have any wiring that might in turn tell the pump to run,
Would it be worth looking for a lose connection

Facelift models have alectrically assisted thermostats, not sure if the link to the electric water pump in any way though.

Could the Thermostat could be stick shut though?

I'm not saying this hasn't also happened but this would not cause the loss of coolant . .....twice !

The OP's bump may have cause electrical issues , but somewhere we have a coolant leak . That needs to be identified and cured first .

 

[cj10jeeper]

I've had a friend round to look at it for the past hour and half. He's a mechanic and I trust is judgement. He tried everything possible to find a leak and bleed the system but it wasn't having it. The pipes from the expansion tank that feed the heater just would not get warm but the water in the expansion tank was steaming hot once that car had go up to temperature. It was as if the water isn't being pumped round correctly, hence the diagnosis that the water pump is toast He's going to get me a price tomorrow.

Does that sound about right? Should I replace the thermostat too?

I think you really need to decide how much you trust this mechanic friend. All I read here are signs that he's running the engine with low coolant, not circulating correctly and getting some parts of the engine very hot.
Seriously you could ruin the engine if you don't sort the leak.
By all means change the water pump if he thinks it's the cause, but stop keep running the engine..

As an aside if the thermostat were stuck shut you'd get very hot water in the heater assuming the system was full of water. They are generally designed to fail open. If you're going so far as to replace the pump I'd put a new stat in anyway.

 

[kammy1975]

Out of curiosity, how much coolant have you put into the system ? You said you had done it twice, and possibly mention that the mechanic also tried, so its got to be quite a substantial leak.

Have to agree with the others, I wouldnt get hung up on the bump, I would look to find the leak, fix that, and take it from there.

Not sure if your OBD reader will necessarily have the access to the error that a failed water pump records in the ECU, as its BMW specific, not generic OBDII error.

I guess you are aware you can run a self test on the water pump to see if thats pushing coolant around the system ? Simply put your key in the car, turn to second position (do not start engine) then hold the accelerator pedal down for over 10 seconds (i beleive its 10secs) The water pump should whirr into life and push coolant around system for something like 12 mins. If your battery isnt in a decent state, make sure you have a battery charger hooked up. If you cant hear the whirring, then take the lid off the expansion tank and check to see if waters moving... theres a few videos on Youtube showing this. Obviously dont do it when the coolant is hot !!!

 

[Chasabi]

Out of curiosity, how much coolant have you put into the system ? You said you had done it twice, and possibly mention that the mechanic also tried, so its got to be quite a substantial leak.

Have to agree with the others, I wouldnt get hung up on the bump, I would look to find the leak, fix that, and take it from there.

Not sure if your OBD reader will necessarily have the access to the error that a failed water pump records in the ECU, as its BMW specific, not generic OBDII error.

I guess you are aware you can run a self test on the water pump to see if thats pushing coolant around the system ? Simply put your key in the car, turn to second position (do not start engine) then hold the accelerator pedal down for over 10 seconds (i beleive its 10secs) The water pump should whirr into life and push coolant around system for something like 12 mins. If your battery isnt in a decent state, make sure you have a battery charger hooked up. If you cant hear the whirring, then take the lid off the expansion tank and check to see if waters moving... theres a few videos on Youtube showing this. Obviously dont do it when the coolant is hot !!!

I'm not sure there is a leak now. As I said in my last reply.... when I removed that bleed screw the coolant level in the reservoir slowly started to rise until the float was in the max level position. To me that means that no coolant has been lost overnight. That doesn't explain where the damp patch came from though. When the mechanic was testing it yesterday there was no sign of a leak.

I think I need to dry everything off and park the car the other way around overnight and see if a damp patch forms, just to be 100% that there isn't a leak. I did try that self test yesterday before the mechanic arrived. I couldn't hear anything whirr into life. I'll watch a YouTube video and make sure I'm doing it right.

I'm starting to think the bump was just a coincidence. I've looked everywhere around the bumper and can't see anything connected to the cooling system that even touches the bumper.

Do you think I would be better off just replacing the 'stat and the pump anyway? Providing I can't find a leak. The zed has done 90k miles now. From what I've read, it's around the time that the water pump usually gives in.

Thank you all for the useful insight Sometimes I think life would be simpler if I'd bought a Fiesta

 

[kammy1975]

Out of curiosity, how much coolant have you put into the system ? You said you had done it twice, and possibly mention that the mechanic also tried, so its got to be quite a substantial leak.

Have to agree with the others, I wouldnt get hung up on the bump, I would look to find the leak, fix that, and take it from there.

Not sure if your OBD reader will necessarily have the access to the error that a failed water pump records in the ECU, as its BMW specific, not generic OBDII error.

I guess you are aware you can run a self test on the water pump to see if thats pushing coolant around the system ? Simply put your key in the car, turn to second position (do not start engine) then hold the accelerator pedal down for over 10 seconds (i beleive its 10secs) The water pump should whirr into life and push coolant around system for something like 12 mins. If your battery isnt in a decent state, make sure you have a battery charger hooked up. If you cant hear the whirring, then take the lid off the expansion tank and check to see if waters moving... theres a few videos on Youtube showing this. Obviously dont do it when the coolant is hot !!!

I'm not sure there is a leak now. As I said in my last reply.... when I removed that bleed screw the coolant level in the reservoir slowly started to rise until the float was in the max level position. To me that means that no coolant has been lost overnight. That doesn't explain where the damp patch came from though. When the mechanic was testing it yesterday there was no sign of a leak.

I think I need to dry everything off and park the car the other way around overnight and see if a damp patch forms, just to be 100% that there isn't a leak. I did try that self test yesterday before the mechanic arrived. I couldn't hear anything whirr into life. I'll watch a YouTube video and make sure I'm doing it right.

I'm starting to think the bump was just a coincidence. I've looked everywhere around the bumper and can't see anything connected to the cooling system that even touches the bumper.

Do you think I would be better off just replacing the 'stat and the pump anyway? Providing I can't find a leak. The zed has done 90k miles now. From what I've read, it's around the time that the water pump usually gives in.

Thank you all for the useful insight Sometimes I think life would be simpler if I'd bought a Fiesta

But that still doesnt make sense. Ignoring the bleed screw for a moment, you mentioned that you added coolant to the system, and it sounded like quite a substantial amount. If I open the radiator cap on mine, the level is high\float rises to the top, but you implied yours wasnt. Maybe when you added the extra coolant, you didnt run the bleed procedure which meant essentially you had air in the system, and when you removed the bleed screw, the float rose to the top as air was released. Something is definitely not right still..

With regards the water pump, assuming it hasnt been changed already, it would be worth changing, as you will only have to do it at some point anyway. However, i wouldnt change it and risk damaging a new one, until you have fully understood the existing problem. Definitely change the thermostat at the same time, as it sits next to the water pump, so the amount of additional labour is negligible. I havent done mine yet, but having watch a few videos, and having asked questions, I think I may tackle it myself when the time comes\when it fails !

Less of the Fiesta talk, you can get banned from forums for such foul language !!!

 

[Chasabi]

Apologies for resurrecting this post. I just thought I'd let you all know that the Zed is now healthy again. It seems that I had a very coincidental pair of events that were totally unrelated. Some idiot smacked my bumper and it just so happened that my water pump died at around the same time!

I never found a leak so went ahead and bought a new water pump and thermostat. Both now fitted and the car is running perfectly. I'm still a little worried that the 10 miles in limp mode while overheating may have caused some unseen damage but for now the engine is running perfectly as before

If anyone is interested, I bought a Pierburg ( Part No. 11517586925 ) water pump from BMWmotorMec on eBay. The required replacement bolts were also included. That cost £246.99. My usual mechanic couldn't find one from his usual sources for less than £400

I also bought a MAHLE Thermostat ( Part No. 11537549476 ) from the same chap on eBay. That cost me £49.99. This one has a plastic body and the one that came off of my car was aluminium (or some other kind of metal) but I don't suppose it matters.

It took my mechanic around 2 hours to fit both and top up the coolant. He charged me £85. Total cost = £381.99. Not as bad as I expected overall.

Just in case anyone stumbles on this thread in future.... don't forget to follow the electric pump bleed procedure once the new parts are fitted. See step 39 on this webpage > http://blog.bavauto.com/14581/bmw-how-to-video-electric-water-pump-replacement-diy-n51-n52-n54-n55-6-cylinder/


Now I've got to get the bumper resprayed then I'm ready for ZedFest in August