[salimshk]

Hi guys,

Hoping someone can help.

Symptoms
Piss poor mpg
Heaters not blowing hot air (or rather intermittently)
Coolant gets to between 88c and 95c but drop well below 88c when the blowers are on full

I recently changed the water pump because it sprung a leak. Sealed all up with gasket and sealant.

Coolant has been changed.

Replaced EGR stat a few months ago (from ECP but original BEHR)

Main stat was changed a few days ago (from Main Dealers)

System has been bled since.

What could it possibly be?

[Sensible_]

Any fault codes?

[rasa bmw]

if water pump was leaking?did you check it for play etc..bearings could be gone,,ive had mine changed on my e90 330d,,but last year when my e46 was elaking,,the waterpump was gone,,loads of play in it,,just a thought

[Silver Streek]

One of your stats is dodgy its the only thing it can be. You do get supplied dodgy ones sometimes. Always get both stats from BMW don't but any for ECP. All the ones I have got from ECP have been faulty.

Take off the EGR stat and test it to see if it is shutting properly, and see if it opens too early.

Also check the system has been bled properly.

[Kjb1]

People give such ill advice on Forums. Look at the facts, your coolant temps are exactly where they need to be!! Around the 85 to 90 degree mark. So, your stats are absolutely fine!!! Your efforts should be aimed at your hvac system in my eyes. One thing it is not, is your stats!!

[Kjb1]

Also for diagnosis, "Piss poor mpg" isnt really a help. What are you classing piss poor mpg as?? Ive had numerous versions of these 3.0d BMW's. And around town, expect anything from 32mpg to 37. They really are not that great on fuel unless on motorway cruising all the time. Still, great performance is the trade off.

[Silver Streek]

Originally Posted by Kjb1

People give such ill advice on Forums. Look at the facts, your coolant temps are exactly where they need to be!! Around the 85 to 90 degree mark. So, your stats are absolutely fine!!! Your efforts should be aimed at your hvac system in my eyes. One thing it is not, is your stats!!

Not quite, re-read what he wrote in his original post. The OP stated that the water temp drops when heater is on full:

"but drop well below 88c when the blowers are on full"

This is will only happen when you stat allows too much coolant through so can't hold temp when heat is lost to the heater. There should be no way that you can loose that much coolant temp when using the heater with a correctly operating stat. Even if the rad was over cooling somehow the stat would close until the coolant temp rises again.

Unless you have trapped air in you're heater matrix.

I'm happy to be proven wrong, but I still reckon you have a faulty stat.

[Silver Streek]

Op when you say the heater is not blowing hot air or intermittently, is the air warm at least?? Does the heater temp go down as you see the coolant temp go down??

[salimshk]

Apologies for the the late response, not sure why I didn't get any notifications of replies to this thread.

1. Fault codes - smooth running control (but was present prior to this problem when my injector was replaced)

2. I put a new water pump on mate, for the price of it and the lack of time I had it made sense to just change it while it was off

3. I changed the my EGR stat under warranty at ECP for another BEHR item but same problem is still there. It seems very unlikely that both would be faulty, the coolant and heating was fine with the ECP stat before the waterpump leak. This leads me to think maybe the main stat from BMW is faulty but what are the chances of that too, considering my issues are identical to what they were before I changed the stat!?

4. Piss poor mpg = 17-21mpg around town. Same journey before coolant problem was 24-27mpg (depending on time of year). I've owned this car for 2 years so when I complain about mpg its relative to my own experience in this car and not someone else claimed figures.

[salimshk]

Originally Posted by Silver Streek

Not quite, re-read what he wrote in his original post. The OP stated that the water temp drops when heater is on full:

"but drop well below 88c when the blowers are on full"

This is will only happen when you stat allows too much coolant through so can't hold temp when heat is lost to the heater. There should be no way that you can loose that much coolant temp when using the heater with a correctly operating stat. Even if the rad was over cooling somehow the stat would close until the coolant temp rises again.

Unless you have trapped air in you're heater matrix.

I'm happy to be proven wrong, but I still reckon you have a faulty stat.

I've tried bleeding the system several times and every time I get different symptoms.

Sometimes it blows hot air but the coolant temperature starts dropping (below 88c) as soon as you increase blower speed.

Other times it will stay within the required coolant temp range but the air will only blow cold (or hot air will come out the face vents and not the footwells)

After the most recent bleed the car isn't even getting up to the 80's in my 20 minute drive to work, however the few days prior to this I was upto 88 within 7 minutes!

So I'm confused as to whether its the stat or perhaps an air bubble in the system. It's been bled so many times though, can't see it being an air bubble. Both top and bottom radiator hoses are getting warm and I squeezed them to push the air out. Am I missing something in the bleeding process?

[Silver Streek]

Sounds like your main stat has failed.

There is a small possibility the main stat may not be seated properly allowing some leakage. But lower MPG and low output from heater can only be due to lower than normal coolant temp. I have had to change main stat 3 times on my old E46 due to faulty units 1 was ECP part and one was main dealer stat BMW swapped part with no quibble, so it does happen unfortunately.

If you have thoroughly bled it, it should be ok in that regard.

[Silver Streek]

When you had different symptoms what was the temperature outside like?? Was the outside temp similar for each of the different symptoms you are getting?

[salimshk]

Originally Posted by Silver Streek

Sounds like your main stat has failed.

There is a small possibility the main stat may not be seated properly allowing some leakage. But lower MPG and low output from heater can only be due to lower than normal coolant temp. I have had to change main stat 3 times on my old E46 due to faulty units 1 was ECP part and one was main dealer stat BMW swapped part with no quibble, so it does happen unfortunately.

If you have thoroughly bled it, it should be ok in that regard.

I feel relieved to hear that main dealer stats do occasionally fail. It was driving me crazy not knowing what it could be.

What is your coolant bleed procedure out of interest before I take the main stat off again? There are several videos on youtube but all the procedures vary slightly.

[salimshk]

Originally Posted by Silver Streek

When you had different symptoms what was the temperature outside like?? Was the outside temp similar for each of the different symptoms you are getting?

The symptoms have been different over the last fewdays and the outside temp hasn't varied by more than a 3-4 C. The only factor that changed was bleeding the system every day

[Silver Streek]

Before filling coolant switch on ignition and turn the heater temp as high as it will go and leave the ignition on. This will open the heater control valve to let coolant flow through the heater matrix. If you forget to do this the valve will stay shut and you can't bleed the heater matrix.

Then I opened the bleed screw on the EGR stat and the screw next to the coolant filler cap, then filled up the coolant slowly. When coolant level was high enough to leak from the EGR stat started the engine then closed the EGR bleed screw, then monitored the other bleed screw as I filled the coolant. I kept opening and closing both valves till no air came out. I then warmed the car till it was hot enough for the main stat to open then bled at both bleed screws again. Just to make sure no air was left after the stat opened.

On my E46 there was another bleed screw in the pipe going from the heater control valve to the heater matrix, when I did a coolant swap the 2nd time I did it I dint touch this bleed screw and it still bled fine. I'm not sure of the E9x have the same bleed screw.

That's about it really, it worked for me.

Just to add the main dealer stat that I put in my e46 lasted about a year before it failed again. Occasionally they do get dodgy batches that make it through to the customers. After market stats seem to be even more of a lottery though.

[salimshk]

Okay so what I did was similar to what you have described above. I ordered from the stat from Cotswold for the forum discount and they have advised to take it to my local dealership for a straight swap. Unfortunately, they are being long about the whole matter and saying they need to inspect the whole car and cannot do so until 11th Feb.

I am sure a dodgy stat doesn't throw up a fault so not sure why they need to diagnose it on the car.

Thank you all for your help. Much appreciated!!

[Silver Streek]

If Cotswolds supplied you with the stat then they are liable to give you a replacement surely.

It's cold outside, I think I would just swallow it and buy another one from you're local BMW dealer and just get it fixed.

Good luck with it, hope you get it fixed!

[Chappers 71]

Originally Posted by Silver Streek

Before filling coolant switch on ignition and turn the heater temp as high as it will go and leave the ignition on. This will open the heater control valve to let coolant flow through the heater matrix. If you forget to do this the valve will stay shut and you can't bleed the heater matrix.

Then I opened the bleed screw on the EGR stat and the screw next to the coolant filler cap, then filled up the coolant slowly. When coolant level was high enough to leak from the EGR stat started the engine then closed the EGR bleed screw, then monitored the other bleed screw as I filled the coolant. I kept opening and closing both valves till no air came out. I then warmed the car till it was hot enough for the main stat to open then bled at both bleed screws again. Just to make sure no air was left after the stat opened.

On my E46 there was another bleed screw in the pipe going from the heater control valve to the heater matrix, when I did a coolant swap the 2nd time I did it I dint touch this bleed screw and it still bled fine. I'm not sure of the E9x have the same bleed screw.

That's about it really, it worked for me.

Just to add the main dealer stat that I put in my e46 lasted about a year before it failed again. Occasionally they do get dodgy batches that make it through to the customers. After market stats seem to be even more of a lottery though.

E9x has electronic self bleeding, link attached below on correct procedure

https://www.google.com/url?sa=t&sour...IWla-1uglqCg7u

[salimshk]

Is that for all e9x's though? Mine is a 2007 m57n2

[Nel2014]

Hi, I have a 320d and have just replaced my waterpump and stat. Both bmw items from Cotsworld and I am having the same problems. When the heaters are on they intermittently start blowing cold air and temp drops to low 70,s. When I,m accelerating it tends to go back up again. Not sure if the 320d stat is the same as 330d but it could be possible that we got a dud batch. I did originally think thermostat wasn't seated properly so took the coolant pipe and housing off and reseated it. Then refilled coolant and bleeded. I'm fairly shore it is fitted ok. Couple of days later still same problem so I'm going to try and bleed again as maybe it could be a airlock in the heater matrix. Only saw one blead screw on the coolant tank though. Will have a look to see if there is one on the coolant pipes going to heater matrix. There are no leaks and the coolant remains level..
Haven't replaced egr stat or temp sensor, there still original.
Also my Water pump is belt driven, not electric. Keep us posted how you get on.

[rasa bmw]

i think you would know about it if you had an airlock,,it would overheat etc,,,cannot remember exactly,,but these cars have wax stats..which are poor design,,i think lci models have different design now...both my cars have had stats done and are fine...i wonder if this cold weather has influenced the wax stat to fail..ill try and find more info on it as its a while since i read about them

[Nel2014]

Yeah my car is an lci model, I replaced the thermostat and waterpump last Wednesday and it was extremely cold (-2). I had the heat on max on blower on lower setting this morning and it got to 80-85 degrees. Then back in to 70's. I then checked up and lower radiator hose after my 1hr journey. The top Water hose was hot but the bottom hose was stone cold..
Heaters blowed hot then warmish air.
Maybe a faulty stat?