Overheating

D

DMC63

Active member
 London
Hi everyone. Well it’s been a while since I’ve been on here and driving my z too. I’m currently sitting in it waiting for the AA breakdown to arrive 😞
Recently the yellow coolant light has come on. The coolant level was s fine. A post on the forum said it was probably a faulty sensor. I drove the car today and the sensor warning light came on again and then after about 45mins driving I could hear the fan kicking in and the temp gauge went up towards the red but i pulled over just before it went into the red so hopefully o damage to the engine. I’ve let the car cool down and the temp is back to the centre. Normal reading again.
Anyone got any ideas what’s happening please? Thanks
 
A failed water pump?
A blocked thermostat?
Head gasket letting go?
Is the coolant still at the correct level?
Does it overheat when properly on the move or only in slow traffic?


More info would help us to help you :thumbsup: I hope you get recovered okay.
 
I hope you get is sorted painlessly OP. :thumbsup:

At least yours doesn't have the electric water pump!
 
wonkydonkey said:
A failed water pump?
A blocked thermostat?
Head gasket letting go?
Is the coolant still at the correct level?
Does it overheat when properly on the move or only in slow traffic?


More info would help us to help you :thumbsup: I hope you get recovered okay.
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Ok, thanks for the replies guys...
Just to put all the info in one post to save you reading back..
1. Yellow coolant light came on a few weeks back. I checked coolant level and the float was ok. Temp gauge normal and stayed normal when driving.
2. Checked forum and post said probably sensor. I thought if it's only a sensor it can wait a few weeks as I'm not driving the car daily.
3. Drove car again for 30min journey twice in one day. Coolant warning light on and temp guage normal.
4. Today drove car for and hour, coolant warning light on and temp guage normal. Parked up and a few hours later drove the same hour journey, not going over 3k revs and mainly around 2k-2.5k revs. Start to hear fan kicking in, coolant warning light on and temp guage normal. Continue to drive for about 10 mins and notice fan still running and suddenly temp guage starts to climb, within 2 mins of the temp gauge climbing I manage to pull over and turn off the engine before the red temp light went on but the guage was nearly there. I called the AA and let the car cool down. The the AA arrived...
Here's the update...
When the AA checked under the hood the float was down, and the undertray was covered in water. He topped up the water and dried around the expansion tank. The expansion tank kept appearing wet on the outside but he could not get a clear look to say it was leaking. I know these crack.
Also only one hose was hot, the others were cold meaning that the water was not circuating.
Another worrying thing was when the AA guy topped it up with water he told me to start the car and then after a few mins the guage hit the red this time with the light on probably a minute or so before I realised and turned the engine off.
I'm now really freaked out that the head gasket has gone...The AA towed me home and will recover the car to my garage free of charge.

The AA guy said that getting a head gasket done is a real pain and that it's often a bit hit and miss as to whether it holds for more than a few months due to the ali engine and torque settings...He was a bit of a BMW head so that's also set me worrying....
 
As you say, the expansion tanks on these cars don't exactly have a gleaming track record. The fact that the outside of the expansion tank was wet also suggests it might have suffered.

I haven't experienced the expansion tank issue myself yet, but failures like this can often work okay when not pressurised, then the crack will open up under pressure and leak. Is that a possibility here? You could check it by topping up the coolant and then getting it properly hot while you inspect for leaks. (Obvious disclaimer: don't get in the way of spurting boiling hot water!)

Question: you say you only had one hot hose. Was this the hose from the engine to the radiator? If all the hoses LEAVING the radiator were cold, this really does rather suggest you're losing water from the rad/expansion tank. I think you can cool it on the head gasket panicking front for the moment until you've got an answer on the radiator.
 
Question: you say you only had one hot hose. Was this the hose from the engine to the radiator? If all the hoses LEAVING the radiator were cold, this really does rather suggest you're losing water from the rad/expansion tank. I think you can cool it on the head gasket panicking front for the moment until you've got an answer on the radiator.
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The hose with the red arrow was hot, all other hoses he said were colder.
The expansion tank from the angle in the pic looks ok but the water was definitely leaking out from somewhere because there was a puddle on the tray and road after he filled it up...

IMG_9368.JPGIMG_9366.JPG
 
Hopefully it's just the expansion tank - they are known for splitting, but I think it's not always easy to see.
 
No mayo under filler cap or on dipstick and no oil residue around collant filler cap or neck of coolant filler opening.
 
Booked the car into the garage (Not BMW) covered by AA parts and garage so that will take the sting out of the tail.
Fingers crossed it's something simple like the expansion tank/thermostat. It had a new water pump last year..
Thanks again for the replies. I'll keep you posted :)
 
It won't be head gasket - it's extremely rare that fails on the M54. New expansion tank defo required (very common failure) + maybe a thermostat. I'd be surprised if it was anything more than that.
 
Funnily enough I've just been doing some work on my car and noticed some water under the passenger side of the front bumper :rofl: Haven't driven the car for a few weeks so it looks like I've been lucky. I'm in no hurry, so have just brimmed the washer bottle to make 100% sure it's not the headlight washer on that side, but the coolant level is low, soooo...looks like I'll be replacing my expansion tank!

Just found this thread, which you may be interested in: https://z4-forum.com/forum/viewtopic.php?t=78833
 
Quick update...Radiator was in a bad state, clogged up and generally 'old'. So that's being replaced, coolant bottle with slight crack, and replacing coolant sensor...So we'll see how it runs once all that's done and keep and eye for signs of head gasket problems...fingers crossed.
The AA have paid the £500 from garage and parts so that's eased the pain.
 
DMC63 said:
Quick update...Radiator was in a bad state, clogged up and generally 'old'. So that's being replaced, coolant bottle with slight crack, and replacing coolant sensor...So we'll see how it runs once all that's done and keep and eye for signs of head gasket problems...fingers crossed.
The AA have paid the £500 from garage and parts so that's eased the pain.
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Fingers crossed for you mate :)
 
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