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

Discuss problems you have had or are having with your Z4
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Chasabi
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Overheating & blowing cold from heaters. Is it definitely the water pump?

Post by Chasabi » Thu Jun 30, 2016 1:36 pm

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

Post by Chasabi » Thu Jun 30, 2016 4:04 pm

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

Post by Smartbear » Thu Jun 30, 2016 4:48 pm

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

Post by cj10jeeper » Thu Jun 30, 2016 5:22 pm

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

Post by Chasabi » Thu Jun 30, 2016 6:21 pm

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

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?

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So at the moment it appears that the coolant is at the maximum level. It's strange :headbang:
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Overheating & blowing cold from heaters. Is it definitely the water pump?

Post by Smartbear » Thu Jun 30, 2016 8:50 pm

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

Post by mr wilks » Thu Jun 30, 2016 8:54 pm

Smartbear wrote: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 :thumbsup:
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 :cry:
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Overheating & blowing cold from heaters. Is it definitely the water pump?

Post by Chasabi » Thu Jun 30, 2016 9:02 pm

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

Post by Smartbear » Thu Jun 30, 2016 10:40 pm

I can't see how the pumps been damaged from a slight scuff on your number plate, it doesn't seem likely?
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Overheating & blowing cold from heaters. Is it definitely the water pump?

Post by Dietcokeman » Fri Jul 01, 2016 6:14 am

Smartbear wrote: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 .

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

Post by markplant » Fri Jul 01, 2016 6:52 am

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

Post by srhutch » Fri Jul 01, 2016 6:57 am

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

Post by Dietcokeman » Fri Jul 01, 2016 10:11 am

srhutch wrote:
markplant wrote: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 .

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

Post by cj10jeeper » Fri Jul 01, 2016 10:37 am

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

Post by kammy1975 » Fri Jul 01, 2016 12:33 pm

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 !!!

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