[AndyVR]

This has just started out of the blue, never had a cooling problem before.

The fan is running at high speed from cold (ambient 10 deg C) , and the car is slow to accelerate (limp mode?) coolant level was ok at minimum mark, I topped up to max.
I did a 20 minute journey where the dash warning for high temperature came up, then quickly after that the warning for overheating/stop driving! I pulled over, the engine didn't seem particularly hot, the top radiator hose was hot, and the lower one was cold. There isn't any heat getting into the cabin, it's stone cold.

The next day I checked the flow of coolant in the expansion tank from cold, there was a good jet of coolant flowing into the tank (from the little hose that comes from the top rad hose connection)
I did a short journey and the fan didn't come on this time, and the car drove fine.

That evening I did a 30 minute drive - fan on from cold, limp mode, no heat in the cabin, but no overheating warnings at all.

I can read fault codes with INPA but I don't have access to my laptop until tomorrow.


Is this likely to be the thermostat , or waterpump? or something else? I guess it can't be just an electrical/sensor problem, with no heat in the cabin ?

It's a 2010 E91 320I N43, I've owned it for 8 years so possibly all the cooling system is original.

Thanks in advance.

[ptpending]

your water pump is dying
this is ok, because its electric
this is well known issue

[AndyVR]

thanks, I didn't realise that it was an electric waterpump - guess it will give out some error codes that I can check tonight.

[ptpending]

its not always drop the code

[AndyVR]

I checked for fault codes via INPA , 3 codes related to the waterpump

2E81 (slow pump rpm/speed deviation)
2E82 (pump shutdown)
2E85 (pump communication)


So it's new water pump time. Seem to be around the £340-£420 mark for an OE Pierburg one!!

[AndyVR]

Still using the car for short journeys while I wait for the part & garage time, but the way the car manages this fault is either nothing at all, or really heavy handed!

I can do city/back road 30-40 minute trips at 30-40mph no problem, the car doesn't overheat or show any warnings, and the engine bay doesn't even seem hot.

Yet if I go on to the motorway (I didn't intend to, but by habit), do a steady 50mph, I got a warning for overheating after just 5-8mins, then pull off at the next junction just another 2 minutes I then get the warning 'Overheating, stop driving' then the engine power decreases and left with no power at all after 2 mins before I've even got off the slip road, so had to pull on to the small bit of hard shoulder!
I left it a few minutes then restarted, 'No faults' reported on the control. Drove normally to get off the motorway properly, then stopped and lifted the bonnet - engine not overheated, fan is off, not even any pressure in the cooling hoses!

I get that the ECU is trying to protect the engine from overheating, but not even allowing a few minutes steady driving to safely get off the motorway or into a safe area is really dangerous! the engine wasn't even hot!

[ptpending]

check the wiring to pump then

[AndyVR]

I replaced the water pump yesterday, the car is running perfectly again, no fan from cold, full engine power, the cabin heater quickly warms up.


The removal and refitting is awkward, as access is poor for spanners or a socket wrench, and your hands!
The way I decided to do it is to leave the thermostat in place, and do it all from above/the engine bay.

The pump is held on to the engine block low down, with an E10 bolt at the top, and two E12 bolts at the bottom. ideally you need a compact 3/8" socket wrench, and a very short extension, as metal parts get in the way.
The lower aircon pipe can easily be unclipped from the front of the engine, and tied to the radiator for more space.

To leave the thermostat housing in place, you have to remove two 10mm bolts where it piggy-backs on to the water pump - these are upside down underneath the pump, and you can only just touch them with your finger tips, through the small space between the pump body and the steering rack below it! there isn't enough space for even a 1/4" socket wrench, so I used a combination of standard 10mm ring/open spanner, and a deep/cranked ring spanner, but it was really difficult, trying a combination of getting one arm down the gap between the inner wing and engine to guide the spanner onto the nuts, and the other arm holding the spanner from the engine bay, but there are so many things for the spanner to foul on (pump body & steering rack) so there is very little room to turn a spanner.
If you do this I'd recommend trying a ratcheting spanner that has the swivel head at one end, or a few different shaped spanners.
Maybe working from underneath the car with the splash shield removed would gain better access, but it was hard to tell as the steering rack obstructs a lot of things.

When the 10mm bolts are removed, the waterpump is freed from the thermostat.

At the back of the waterpump is it's electrical connector - probably one of the
easiest electrical connectors I've ever removed - squeeze the release tab and wiggle the connector off.

The pump has two water hoses at the front, they are clamped with jubilee clips. A hose removal tool would of been useful, but i used a big blunt screwdriver to free them off the pump. Use a shallow tray under the splash shield to catch the old coolant, approx 3 litres came out.

Now the old pump can be removed from the engine bay.

Refitting can be fiddly done this way - I recommend loosely fitting the hoses and putting the 10mm bolts to the thermostat in first, so the pump can be moved around for more space - it's difficult here to get the 10mm bolts through the pumps into the thermostat from underneath, almost blind, without dropping them. (I recommend a telescopic magnet tool for retrieving dropped bolts and spanners!) again, it's difficult to tighten the bolts.

Now the pump can be bolted back up to the engine block - careful here as the rubber bushes on the pump legs can fall out if the bolts catch them! this is annoying when trying to get the pump to line up with the holes on the block, when you're already tired and you've banged your head for the 100th time!

When the bolts are tight, plug the electrical connector back in, fit the jubilee clips to the hoses, then refill the system from the expansion tank with your premixed coolant & water.

Run the electric water pump bleeding procedure - Ignition on, heater set to max heat, hold the throttle to the floor for 10 seconds - now the water pump will cycle on and off for 12 minutes, you will hear the air gurgling through the hoses and out through the expansion tank. When that's done, top up with coolant mix to the correct level, and refit the tank cap.

Maybe a better way is to do the extra work of removing the thermostat housing so it can stay attached to the waterpump?

Hope this guide is useful to an N43 owner.