Pistratoaie

Hi all, Got an issue on 2005 525i M sport.
First off, had radiator replaced after it was found leaking, before this, I know that the engine temperature was at the last two bars on the rev limit on dash. Here's where the problems start...

Picked up the car from shop, drove normally for 10mins and then noticed heating wasn't working/slowly dying as I was turning it up on the drive home. Thought it was just new coolant and radiator so all was just cold? Next morning, for 50km drive had no heating and engine temperature was really low (ie. lots of bars on the dash meter). That week I drove 500km and had no heat but same low engine temperature. Took it back to shop next week and got thermostat replaced.
Picked it up today and had heat for drive home (thermostat was faulty so replacement was necessary regardless) later on in the day, very little heat, and engine temperature is maxing at 70*C (on hidden menu coolant sensor temp reading)...

Sorry it's long, I like to be as detailed as possible, Any ideas on what's going on here? would a faulty temperature sensor cause the low engine temp and almost no heat inside the cabin? Water valve? Would like some info before I take it back and they just replace parts randomly

twh

Not sure I have any spot on advice. A bad water pump might cause less heat to be available for the climate control, but the car would also overheat and you'd get a message about that. Is the shop a BMW shop? There is a specific coolant air bleeding procedure. If that isn't done, you can end up with air pockets in the system and maybe that could manifest as you are seeing??

I'm pretty sure there is some kind of water value for the climate control heating system.

Pistratoaie

I've got my fingers crossed hoping it's not the water pump, but as you say it has got to be water related. The shop is a Euro specialist, and the guy working on my car is an ex BMW tech, so I've got some credibility in these guys. I went back the next day to get the bleeding procedure done again, and I checked their method which was all to specification.
The other thing is, no error codes show up, hence why we ruled out the water pump. So no error, and no overheating (quite the opposite is happening instead), and erratic heat responses
I suspect a sensor, water valve or heat exchanger?

twh

Go to Realoem.com and find your car. There is a valve in the climate control heat circuit. You should find that valve under the hood and test it out. I've had two other cars in my lifetime that had a faulty valve there and it prevented the heater from blowing hot.

Not sure this is your exact model or not:
RealOEM.com Diagram Selection

Quarta2six

If Im not mistaken I think a Thermostat stuck in the open position will cause low temp and little to no heat. I would think an CEL would be thrown though

Pistratoaie

Fuuny you should mention, mechanic thought it might've been this valve too, before changing the thermostat. But would this have anything to do with engine temp being low? isn't it only related to heating?

Thermostat was the first thing to suspect, It's a new one in there now but still same problem. Unless I've got a rare occasion where the new thermostat is faulty searching Realoem, I've come across another thermostat (no. 13: RealOEM.com * BMW E60 525i MOUNTING PARTS F RADIATOR) could this be a cause of these issues? and yeah no errors whatsoever...

Pistratoaie

Update, been a hectic few weeks where I've been with the car away and couldn't take it in for necessary works. I've got the thermostat and water valve (heater tap) replaced.
Now, I get heat quicker when starting up in the mornings so that's a relief, however the heat drops off and blows slightly warm when I'm exceeding speeds above 70kph
Still no error codes, what is going on??? I'm pushing for a thermostat change again by mechanic to see if the new part is faulty...

steve-savalas

Have you enabled the coolant temperature display on the dash to make sure that the coolant is actually getting up to the correct temp? If it is, then your thermostat is obviously fine and you're looking at another issue.

Pistratoaie

On the cluster? Yes I've checked the KTMP temp throughout a 2hr drive, and it was at 72-77 almost the whole time. There were some times when it would reach 88 and one time 98, but then it'd drop back to the mid 70's. I do have a new sensor/fan switch to test that out on Monday 29th when it goes in for full day testing and checks at mechanic. So... still the stat sounding like the main cause?

steve-savalas

Yes, definitely sounds like the main stat. When the temp got higher i'm betting you were in slow moving traffic, or stationary. Then as soon as you speed up the temp drops again dje to the stat being stuck open. Did the heaters work ok when the temp was 90+?