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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Mechanical Maintenance: Break-in / Oil & Fluids / Servicing / Warranty > Coolant warning and limp mode



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      01-31-2011, 02:33 PM   #1
chesney72
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Coolant warning and limp mode

Very weird and I was thinking this was looking like a failed elec water pump but why would it do this then clear and drive faultlessly???

Happened coming home tonight. 10mins into my drive home I gave it less than half throttle and it was flat as a pancake. Wouldn't boost. Seemed ok with light throttle but more like limp mode. 5 miles later I get a coolant temp warning folowed by the overheating warning and as I stopped I could hear the cooling fans blaring.

Openned the hood and thought it was odd as there wasn't the usual blast of heat you get let alone more heat resembling overheating. The coolant pipe into the top radiator was as hot as normal but the top of the engine wasn't hot at all! A I shut the hood there was a puff of steam so I openned up but couldn't see any leaks. Coolant level was where it should be.

Restarted the car and it ran faultless all the way home. I'm not convinced it was overheated as I've openned the hood to top up with washer fluid before and you can normally feel a lot of heat from the engine......tonight I had my hands on top of the rocker cover and it was fairly cool and def not hot. Little heat coming up from the turbo's but certainly not hot as I had been gently cruising at 2k rpm max.

So why the limp mode, coolant warning but no apparent leak or excessive heat from engine? Possible thermostat sticking but that would surely make the engine very hot to touch.

If the pump had failed then when did it then run for 30 more miles trouble free and at full power?

No engine warning light so its not HPFP issue.

Overheating suggest water not flowing but surely these pumps just die and thats the end of it or is it just warning me the next time it will! WHy would I get limp type symptoms and no warning lights til 10 mins later.

WOuld a faulty temp sender send flickering signals to the ecu hence the limp and then it spikes and tells me its overheating when it maybe isn't.

WIll try to get it checked for faults soon as but wonder if anyone has had this
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      01-31-2011, 02:49 PM   #2
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I don't think you have to have a leak for the coolan warning to appear. It could be a fault code coming from the thermostat or the water pump valves getting stuck in the on/off position. Have it check out by the dealer just to be on the safe side. It is an electrical system and can have several complication beside leak. Post back what you find out. GL.
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      01-31-2011, 03:18 PM   #3
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Quote:
Originally Posted by txusa03 View Post
I don't think you have to have a leak for the coolan warning to appear. It could be a fault code coming from the thermostat or the water pump valves getting stuck in the on/off position. Have it check out by the dealer just to be on the safe side. It is an electrical system and can have several complication beside leak. Post back what you find out. GL.
Cheers for the reply.

Water pump valves sticking sounds like a possible cause of the coolant temp issue and suppose a stop and restart could have been enough to free them up and got me home ok. But would that cause it to feel like limp mode? Suppose if the temp sensor sent a high enough reading to the ecu then it might cause limp but question then is why wouldn't it throw up a warning as soon as it hit limp.
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      02-02-2011, 02:36 AM   #4
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Bit more info.

Ran the car on my regular commute but had the hidden menu showing the temp. Got up to around 90-93C as expected but did a couple of odd things.

First was when going up a hill so I would expect the engine is under load but the temp dropped to 76C for a couple of mins then went back up to 90-93C.

Secondly when sitting in traffic it rose to 105C. No coolant temp warning though??

I am thinking this might be a dodgy thermostat. What sort of operating temps should this engine run? I had thought it would sit around 90C and shouldn't ever get over 100C (Boiling!!).

Could still be the pump. I'll make arrangements to have it checked this weekend.
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      02-02-2011, 12:48 PM   #5
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Ok, I think the overheating ISN'T actual overheating.

Ran car home and the temp display seemed to fluctuate a bit. I was losing the power again when the temp was around 78C. Lasted a couple of min then came back.

I'm thinking its a temp sender now after this happened:

Over took a car and then backed off. temp was increasing slowly, I felt the loss of power then the temp started to rise very very quickly. I pulled over and it rose to 120C then the light came on. I switched off then restarted the car and the temp them dropped very very rapidly to about 88C

Def something amiss with a temp signal. Waiting on a fault scanner tool arriving and will check it out myself before going to the dealer.
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      02-23-2011, 02:32 PM   #6
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This was confirmed as the water pump by the dealer.

It was intermittent then last weekend the waterpump wouldn't switch off when the car was switched off and it ran until the battery drained!

Not a cheap repair, you'll be looking at around 700 to have this sorted. Mine was luckily under warranty but they are currently being stubborn and refusing to pay the 2 hrs to diagnose the fault even though they chose the dealer to take it to

I will name and shame if they don't wise up
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      11-12-2011, 10:00 AM   #7
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I have the same problem but the water pump seems to work. Have you monitored your temps since the water pump change? My temp seems to fluctuate, and then work fine once. Wondering if the t-stat managed to get stuck closed?
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