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Hi all, looking for some advice on an E86 3.0si with a weird cooling problem.
Recently the interior heater will not blow any warm air. If you keep driving it the temperature gauge starts to rise and fall quickly (between middle and red). Stopping and starting the engine sometimes fixes it.

Its been into my local garage twice. Most recently they said it had air in the cooling system and a flush fixed it. I went to pick it up just now and the following happened:

- Drove 10 mins home, temperature gauge went to middle, no heat at all from heater
- Stopped the car at home, restarted a couple of times, still no warm air
- Drove 10 mins back to the garage, the temperature gauge started to rise and fall, eventually resting near red, still no warm air
- Switched the car off, left it 10 mins whilst I spoke to the garage
- Switched the car on, temperature gauge was in the middle, interior heater was nice and warm, drove 10 mins home with no issues

My garage seems to think its the head letting air into the system and has suggested I speak to a BMW specialist. Any thoughts?

Cheers.

Sounds like the water pump fault that very common on that engine. I don't have direct experience if that fault on that engine myself but plenty do on here. Hopefully someone can confirm it.

As Mack says the Electric Water Pumps on the si are prone to fail - but usually they fail abruptly and without warning and your temp gauge climbs into the red and stays there until the pump is replaced.

Thanks both - yeah my initial thought was water pump but I assumed if the pump failed it would overheat really quickly? Whereas mine is sometimes fine and letting the car rest for a bit and restarting often fixes it.

Wajakel wrote: ↑Mon Nov 13, 2017 4:58 pm Thanks both - yeah my initial thought was water pump but I assumed if the pump failed it would overheat really quickly? Whereas mine is sometimes fine and letting the car rest for a bit and restarting often fixes it.

some have reported them failing in a weird way, rather than a full blown fail they simply seem to fail to kick in on startup and work fine the next time..

Wajakel wrote: ↑Mon Nov 13, 2017 4:58 pm Thanks both - yeah my initial thought was water pump but I assumed if the pump failed it would overheat really quickly? Whereas mine is sometimes fine and letting the car rest for a bit and restarting often fixes it.

Hi, how old is your car & how many miles has it covered?
Rob

Water pump for sure. Don’t drive it until you have changed it. If you cook the engine you are looking at big repair bills.

Sounds like the pump to me too. Have you tried going through the bleed procedure again? It is known to take a couple of goes to get rid of all the air

Smartbear wrote: ↑Mon Nov 13, 2017 6:32 pm

Wajakel wrote: ↑Mon Nov 13, 2017 4:58 pm Thanks both - yeah my initial thought was water pump but I assumed if the pump failed it would overheat really quickly? Whereas mine is sometimes fine and letting the car rest for a bit and restarting often fixes it.

Hi, how old is your car & how many miles has it covered?
Rob

2006 & 118k

Silverzedtom wrote: ↑Mon Nov 13, 2017 7:06 pm Sounds like the pump to me too. Have you tried going through the bleed procedure again? It is known to take a couple of goes to get rid of all the air

Just followed the guide for the bleed procedure and the water pump didn't seem to startup. I've never done it before so I'll give it another go when its not dark and raining. Could indicate the pump has failed though?

If the pump isn’t starting whilst going through the bleed procedure then it sounds like more evidence for a knackered pump. Don’t forget it’s a good idea to connect the car to a power source as the procedure is a big drain on the battery.

Not sure what dealers / indies are charging for the labour but if you decide to DIY then here’s a link:
viewtopic.php?t=18804

If nobody has found an easier way then it looks like you’ll need to know your way around a set of spanner’s after skimming through those steps.

Hope you get it sorted soon

Wajakel wrote: ↑Mon Nov 13, 2017 7:27 pm

Smartbear wrote: ↑Mon Nov 13, 2017 6:32 pm

Wajakel wrote: ↑Mon Nov 13, 2017 4:58 pm Thanks both - yeah my initial thought was water pump but I assumed if the pump failed it would overheat really quickly? Whereas mine is sometimes fine and letting the car rest for a bit and restarting often fixes it.

Hi, how old is your car & how many miles has it covered?
Rob

2006 & 118k

At that mileage this may even be a second pump failing. The reports on here seem to be 60-80k as the usual range. I guess your car could still be on the original one though. As buckz said earlier there are few reports on here of them failing intermittently before packing up completely which sounds like it might be the case here.

Silverzedtom wrote: ↑Mon Nov 13, 2017 8:01 pm If the pump isn’t starting whilst going through the bleed procedure then it sounds like more evidence for a knackered pump. Don’t forget it’s a good idea to connect the car to a power source as the procedure is a big drain on the battery.

Not sure what dealers / indies are charging for the labour but if you decide to DIY then here’s a link:
viewtopic.php?t=18804

If nobody has found an easier way then it looks like you’ll need to know your way around a set of spanner’s after skimming through those steps.

Hope you get it sorted soon

That guide is not for an N52. Completely different. It’s an easy 1hr diy. £250 for the pump and I’d be changing the stat also at that mileage.

Sounds like pump - Mine failed at 118-119k miles.
That was my car's first one too.

Mine failed gradually over the course of a couple of months so they don't always go the same way,

If you have an OBD reader you can do a fault code scan on the free version of the carly app to confirm.

Order the pump from Germany much cheaper than the UK suppliers even with shipping accounted for.

I didn't bother replacing the stat as the mechanic said its a piece of piss to get in and change if it ever fails so not worth replacing unless it throws up a fault