Andrew Posted August 7 Share Posted August 7 Started car up first thing this morning. Cooling fan starts off at high speed. Engine is stone cold. Switch A/C off, fan continues to intermittently spin at speed. That's not right, the cooling fan is spinning with a stone cold engine. As I set off for work without any other untoward symptoms the fan kicks in and out at higher speeds than normal. I can hear it as I slow in traffic. After 15-20 miles, I'm now on the M77 heading south from the M8 which is on a slight grade, but as the limit is only 50 mph I sit keeping up with the traffic between 50-60 mph when I get an yellow engine high temp warning on the dash saying "Proceed to nearest dealer" and all that stuff. Engine oil temp gauge is normal and still on the cold side of vertical. Oh bother. I'm thinking something isn't right and I must be linked to the cooling fan running when engine was cold. My line of thought being car thinks its hot when its not. I pull off at the next exit within a few hundred meters and coast down the off ramp heading towards a supermarket car park where I know I'll be safe, the dash warns of too high engine temp and I get a red engine high temp warning. Engine oil temp gauge is still normal and still on the cold side of vertical. Oh bother bother bother. Within seconds the red warning disappears and its replaced by the yellow warning. Park up in the car park and open the bonnet. No signs of coolant spewing out. No burning smells, absolutely no signs of carnage that I was expecting with an overheated engine. But and this is what has puzzled me, the radiator is stone cold. It was only 12 degrees outside and I had been only pootling along at 50-60mph. Could I have not got the coolant up to thermostat opening temps? I then run the electric water pump as per. I hear the pump run and the oil temperature gauge drops. So the pump is working, well now atleast. After 10-15 mins the oil temp gauge has dropped to halfway between 70 and 120 deg. I set off towards East Kilbride via the slower roads. I drive with the heater set to max heat and again I can hear the cooling fan kick in as before. The oil temp gauge stays at halfway between 70 and 120 deg. I arrive at the office and the fan is now running full chat. Again radiator is stone cold indicating to me that the thermostat has not opened. Hmm During my lunch break about four hours later, I access the hidden menu to read the engine temps. As you hear in the video above the fan is not running. Oh joy, an intermittent fault. No EML light either. I order up a thermostat and a temp sensor delivered for £50. I await their arrival. A further 4 hours or so, I gingerly set off for home, this time I drive home with the temperature displayed from the hidden menu. I can hear the fan again running as before as the engine heats up but not as often. Oil temperatures exceed 108 deg C which is fine. Thermostat on comfort mode opens at 103 deg C. Water temperature fluctuates with varying degrees of power/coasting. I reckon that once the water temp got up to the thermostat opening temperature, the cooling fan ceased to operate excessively and all was well on my way home. Once home all was well under the bonnet and the radiator was hot, so I know the thermostat was operating and allowing flow thru the radiator as observed with the water temp figures fluctuating slightly between high 88 and 105 deg. Couple of hours later I go and retrieve fault codes. Oh bother as suspected water pump is in the process of failing. A Google had thrown up many many forum posts on "My N55 cooling fan runs at full speed when engine is cold" complaints, just like my first symptom. And of course none of these threads have any retrieved fault codes as most seem to relate to 135i drivers and fault codes are obvs not their forty, probably too complicated for them. One or two suggestions that its a sign of a failing water pump and you need to read the codes but no one ever did. Until I come along and confirm that the symptoms of a failing water pump are indeed a cooling fan running far faster than it normally does in an effort to keep things cool. I cleared the codes and operate the pump via my Foxwell. Seams ok? I take it out on a test drive with @VPCAPTAIN in the co-pilots seat with the hidden menu up to monitor temps. All fine as trip home, no fan running excessively and radiator was hot. I check the water pump operation via the link above and it sounds not quite so healthy this time and then check for fault codes. So that's a confirmed kill with the water pump being on its way out. I doubt its a blockage, more likely the system is detecting an increase in current going to the pump motor due to it failing. It physically can't detect a blockage but can monitor power/voltage/current being used by the motor in the pump. Engine appears o.k. MPG is normal and improved on my way home, stop start worked as usual indicating that all is well with many systems. I've made a few enquires on sourcing a new water pump. Wallet is braced for a pounding. 1 Quote Link to comment Share on other sites More sharing options...
Kopfjaeger Posted August 8 Share Posted August 8 It would be interesting to know what the Car's mileage is and what pump is fitted. My F07 has two listed in RealOEM and I think one was a lot more expensive than the other version. I vaguely recall someone suggesting replacing a water pump around the 50k miles, but that could be an old wives tale. There is a possibility that the pump impeller has failed? If a blade has broken off, it can become an intermittent blockage and also be the cause of increased power draw, as fewer blades try to maintain flow in the circuit. If the engine runs and the radiator is cold, then there is no coolant flow....so the pump isn't working, or possibly intermittently. Either way, sounds like a bench inspection of the pump is required. 1 Quote Link to comment Share on other sites More sharing options...
Andrew Posted August 8 Author Share Posted August 8 4 hours ago, Kopfjaeger said: It would be interesting to know what the Car's mileage is and what pump is fitted. 67,400 miles and I think its a Continental pump that's fitted. The Conti pump has a black plastic impeller housing. A Pierburg pump has a metal impeller housing. 4 hours ago, Kopfjaeger said: There is a possibility that the pump impeller has failed? If a blade has broken off, it can become an intermittent blockage and also be the cause of increased power draw, as fewer blades try to maintain flow in the circuit. Well it was firing water out as normal when tested using diagnostics, so something isn't right. I reckon its wearing out and sometimes it works and sometimes it doesn't. Cooling system was flushed in October last year and coolant replaced. 4 hours ago, Kopfjaeger said: If the engine runs and the radiator is cold, then there is no coolant flow....so the pump isn't working, or possibly intermittently. My thoughts are: If the thermostat won't open then there will be no flow thru the radiator even if the pump is working. You should still get some flow via natural convection* with the thermostat open and no pump running and the heater was certainly pumping out heat continuously so coolant must have been circulating. * perhaps it was and with the fan running as it was it was able to easily cool what was flowing thru the radiator? I've ordered and new Mahle one (OEM) for £48.95. Genuine one is over £100. Quote Link to comment Share on other sites More sharing options...
Kopfjaeger Posted August 8 Share Posted August 8 Hearsay suggest the latest Pierburg pump which is an all metal casing and has a metal impeller is an upgrade on the ones originally fitted by BMW. Which have/had plastic impellers, etc. Plastic does degrade with heat, especially when it's cycling, e.g. ambient through to 100 degrees C plus environments. Based on your mileage and if it has a plastic impeller, it's likely to be approaching end of life. Quote Link to comment Share on other sites More sharing options...
Kopfjaeger Posted August 8 Share Posted August 8 Here is the link to the upgraded pierburg pump https://oembimmerparts.com/blogs/news/bmw-n54-n55-upgraded-water-pump-is-now-available Water pump life expectancy is in the 65-75k miles, so yours in at the bottom end of the range. Quote Link to comment Share on other sites More sharing options...
Andrew Posted August 8 Author Share Posted August 8 I did a plastic to metal upgrade (impeller) on my E39 water pump. It cost less than £40 from Euro Car parts back in 2005..... What mileage is on your N55? Quote Link to comment Share on other sites More sharing options...
Kopfjaeger Posted August 8 Share Posted August 8 Mine is about 36.5k at 7 years, 9 months old. Quote Link to comment Share on other sites More sharing options...
Andrew Posted August 8 Author Share Posted August 8 13 minutes ago, Kopfjaeger said: Mine is about 36.5k at 7 years, 9 months old. Nice. Get the water pump, thermostat and oil cooler gaskets on a to do list. 🤪 Quote Link to comment Share on other sites More sharing options...
Kopfjaeger Posted August 8 Share Posted August 8 They're already on the PPM list, but I'm unlikely to tackle these myself. They'll be delegated to a trustworthy garage.....just need to find one😊. I have a really good garage I've used for nearly 30 years, but they aren't BMW specialists. Quote Link to comment Share on other sites More sharing options...
Steve84N Posted August 8 Share Posted August 8 I changed the water pump and thermostat on mine before the new engine and it was on around 95k miles, 12yrs old. Pretty sure it was original so there's no hard and fast rule for changing. If it's over 10yrs then I reckon you're in the danger zone regardless of mileage though. Quote Link to comment Share on other sites More sharing options...
Andrew Posted August 8 Author Share Posted August 8 What make of pump and ‘stat did you go for @Steve84N? Quote Link to comment Share on other sites More sharing options...
Steve84N Posted August 8 Share Posted August 8 @Andrew Pierburg metal pump and Mahle thermostat. 1 Quote Link to comment Share on other sites More sharing options...
Andrew Posted August 8 Author Share Posted August 8 Yeah the Pierburg is all aluminium, the Continentals have a plastic impeller housing. Pierburg are OEM for Porsche I think and get good press. Good price too compared to others. https://www.partsinmotion.co.uk/car-parts/cooling-heating/water-pump/pierburg-7-07223-10-0-water-pump-7-07223-10-0-detail Still a plastic impeller tho in them. I’ve a Mahle thermostat on order. Behr is OEM but they are now part of Mahle and Mahle are OEM for other bits so that’ll be rightly. Quote Link to comment Share on other sites More sharing options...
Steve84N Posted August 9 Share Posted August 9 People say it's the electronics that give up more than the actual impeller, hence the more random nature of when it fails. 1 Quote Link to comment Share on other sites More sharing options...
Andrew Posted August 9 Author Share Posted August 9 1 hour ago, Steve84N said: People say it's the electronics that give up more than the actual impeller, hence the more random nature of when it fails. Exactly what I've read too. If the electronics say no, then it won't work. 😩 Heat cycles along with vibration aren't delicate electronics best friend I'll be taking the old water pump to bits once I've swapped it out the see what's what. 1 Quote Link to comment Share on other sites More sharing options...
Kopfjaeger Posted August 9 Share Posted August 9 That'll make a good read😊. I'd be interested to see pictures of the impeller to see if there is any wear, or worse, evidence of pitting, which indicates cavitation ( air bubbles rupturing/ collapsing, creating shock waves). Cavitation doesn't care what material is used. Metal impellers are usually superior to plastic. However, plastic impellers don't corrode. 1 Quote Link to comment Share on other sites More sharing options...
Andrew Posted August 9 Author Share Posted August 9 27 minutes ago, Kopfjaeger said: However, plastic impellers don't corrode. No but in the case of the E39 water pumps the plastic impellers would quietly and simply detach themselves from the drive spindle and you would be none the wiser until the needle went to the red! 🤦♂️ Quote Link to comment Share on other sites More sharing options...
Kopfjaeger Posted August 10 Share Posted August 10 Precisely why plastic impellers are useless. If I had iron man's workshop, I'd get it to fabricate parts for longevity in my F07.😊 1 Quote Link to comment Share on other sites More sharing options...
Kopfjaeger Posted August 10 Share Posted August 10 Sad isn't it? I must be getting old. I wouldn't say no to the suit though. Save on petrol going anywhere and no speed cameras to worry about.🤣 Quote Link to comment Share on other sites More sharing options...
BobA Posted August 10 Share Posted August 10 @Andrew so what caused/causes the cooling fan to run at high speed at startup when the engine is cold and long before any heat sensor can have triggered? Is there something to sense circulation rather than just temperature? Quote Link to comment Share on other sites More sharing options...
Steve84N Posted August 10 Share Posted August 10 @BobA the fan runs as a failsafe. If you can't sense that the engine is OK you assume the worst and it needs cooling. That helps avoid it overheating when sensors fail. 1 Quote Link to comment Share on other sites More sharing options...
BobA Posted August 10 Share Posted August 10 (edited) Thanks. Didn’t know that though it seems sensible. But my question is really what was deciding that @Andrew’s engine was ill so soon after startup from cold before the engine temperature sensors would have triggered? Is there something which detects a lack of coolant circulation? Edited August 10 by BobA Quote Link to comment Share on other sites More sharing options...
Andrew Posted August 10 Author Share Posted August 10 @BobA When you switch on the ignition every module communicates with each other and their driven components, such as water pump, blower motor, fan etc etc. Because BMW like making things complicated, there are four pins on the electrical side to the water pump. One earth, one main power, one switched power and another a signal line which is why when it fails it can leave a fault code and talk to modules on start up. As the problem is with the electrics in my water pump it knows (before I do) that something isn’t well so it does a fail safe as @Steve84N says. To protect the engine against the broken water pump it puts on my fan at full chat so it’s pulling cold air from outside thru the kidney grills over the engine to try and cool it. It’s a big fan and it pulls a lot of air, I could physically feel it pulling air in to the engine compartment 1 Quote Link to comment Share on other sites More sharing options...
BobA Posted August 10 Share Posted August 10 Thanks - still learning after several Beemers! 1 Quote Link to comment Share on other sites More sharing options...
Andrew Posted August 10 Author Share Posted August 10 35 minutes ago, BobA said: Thanks - still learning after several Beemers! Oh yeah every day is a school day. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.