Coolant temperature in the red.. engine tray wet.. what's wrong?

D

dmo

Member
 London / Surrey
As the title suggests..

I used my Z4C on Saturday after 2 weeks of it sitting on my driveway - last time I used it, it was all good!

About 3 miles into my drive (10mins) my coolant light went into the red and gave me a beep :? I stopped and had a think, checked the engine bay which was dry at the time. Stupidly I opened the coolant reservoir and let out some of the coolant as it was pressurised. I continued on my journey again and got about a mile and a half down the road before the temperature rose again. Parked for half an hour and did the final 2 miles to bring it home.

This evening I topped up the coolant with some water to bring the bob back up to level. Drove it for 7 mins (2.5 miles) - all was good. I thought perhaps the other day was an anomaly having not used the car in a while. On my way back I was going to hit the A3 to give it a good run (thinking maybe it needs to just be driven a bit after a few weeks of sitting) - and the temp kicked up again. I parked up and let it cool and stuck a torch in the engine bay and noticed a LOT of water/coolant perhaps sitting on the tray under the engine bay. Looked freshly split... so I'm wondering if it could be coming from the coolant pipes? The temperature went through the roof and I just managed to get it back, had to stop 3 times in the last mile as it kept going into the red. :headbang:

Might be worth me nothing that this last happened in January after a few weeks of the car sitting on the drive while I drove down to get it serviced / MOT'd, although the coolant temperature went down after letting it sit for 10mins or so; that day it was a freezing day (in the minus / zero range).

Where should I start with this one? I can't see where the leak is (if there is a leak); am I right in thinking a leak could be related to the coolant temperature warning? Any help appreciated...!
 
Might be your coolant reservoir cracking (known fault).
They dont show leaks until the engine gets warm->coolant under pressure and then it squirts out a tiny little crack.

Maybe also look at your electric coolant pump. The speed that your engine overheats is quite fast.

There are special kits to pressurize the system to look for leaks without the engine getting warm.
I have this set:
http://www.ebay.co.uk/itm/12PC-Car-Pressure-Test-Radiator-Coolant-Cooling-System-Leaks-Tester-Detector-Set-/222204453471
 
The water temperature sensor probe (located in the top hose by the thermostat housing) has a small o-ring that also can leak coolant down onto the undertray without much evidence when looking from above. When the engine is warm switch off and run your fingers round the temp sensor connector and if its wet you need a new o-ring. :thumbsup:
 
patriot66 said:
The water temperature sensor probe (located in the top hose by the thermostat housing) has a small o-ring that also can leak coolant down onto the undertray without much evidence when looking from above. When the engine is warm switch off and run your fingers round the temp sensor connector and if its wet you need a new o-ring. :thumbsup:
Click to expand...
Thanks a lot, I'll have a look.

Do you think that can also trigger the coolant to go into the red?, that's what really alarmed me!

Also, do you think you could provide a picture of where to look? I'm normally alright at this stuff, but have found it impossible to find the temperature sensor for some reason. Is it concealed somewhere?

Edit: Is it this http://images.esellerpro.com/2493/I/178/08/o%20ring.png
 
The o ring he means is I think part of sensor #5

http://bmwfans.info/parts-catalog/E85/Europe/Z4_3.0si-N52/browse/radiator/cooling_system_water_hoses/#pos_5
3khi.png

You cant order that o ring directly, but O ring #4 in next link is the same o ring (saves you to buy the complete sensor):
http://bmwfans.info/parts-catalog/E85/Europe/Z4_3.0i-M54/L-N/mar2004/browse/engine/intake_manifold_system/
2yrh.png

That O ring is a known leak but I doubt it can leak so much that it can describe your problems.

You should be really careful with driving with a hot engine. It can blow your headgasket, warp your head and weaken the aluminium structure of the block.
If/when your coolant light goes on, it means that you have lost about/almost 1L of coolant
 
In my experience, it will be either the expansion tank or the thermostat housing.

Remove the undertray, run the engine and look from underneath to find out where it's leaking from.

Front centre, it'll be the thermostat. The gasket goes brittle over time, causing leaks.

Front right, usually expansion tank cracked.
 
I hope it's not the waterpump, this car uses the n52 engine & the pumps are pricey. How many miles has your car done? Anything over 70k and the pumps are prone to failure :o
Rob
 
When your car displays signs of overheating stop immediately and get it towed to a garage. If you drive an overheating car you will run the risk of either warping the head or damaging the engine. Take it to your local garage to get it fixed.
 
Smartbear said:
I hope it's not the waterpump, this car uses the n52 engine & the pumps are pricey. How many miles has your car done? Anything over 70k and the pumps are prone to failure :o
Rob
Click to expand...
Its done just 35k; bought it 4yrs ago with 27k on the clock. Weekend car.
 
GuidoK said:
The o ring he means is I think part of sensor #5

http://bmwfans.info/parts-catalog/E85/Europe/Z4_3.0si-N52/browse/radiator/cooling_system_water_hoses/#pos_5
3khi.png

You cant order that o ring directly, but O ring #4 in next link is the same o ring (saves you to buy the complete sensor):
http://bmwfans.info/parts-catalog/E85/Europe/Z4_3.0i-M54/L-N/mar2004/browse/engine/intake_manifold_system/
2yrh.png

That O ring is a known leak but I doubt it can leak so much that it can describe your problems.

You should be really careful with driving with a hot engine. It can blow your headgasket, warp your head and weaken the aluminium structure of the block.
If/when your coolant light goes on, it means that you have lost about/almost 1L of coolant
Click to expand...

Thanks a bunch. So I'm not sure there's even a leak now.. because i realised the stuff that leaked on Saturday probably never dried when I checked it on Sunday night last week. Even now, 5 days later, it hasn't dried (it's antifreeze afterall...)

I'm wondering if its a sensor problem afterall... and hoping the leak was from when I opened the expansion tank whilst it was hot.

Annoyingly, I can't spot exactly where the sensor is
 
Is it this, or like this? http://i259.photobucket.com/albums/hh284/lpcapital/Cars/pic02.jpg
 
My money would be on thermostat (only because this has happened to me before and that was the fault). Probably plenty of other explanations
 
Good luck fixing this soon.

Just get it to a garage to diagnose correctly, as others have posted you do not want to be driving an overheating engine and cause more expensive damage.
 
Probably expansion tank, mine cracked this year. They usually let go around 80k
Mine had a hairline crack where the bottom hose joined. You can reach in through the passenger wheel arch to the expansion tank to feel about for any leaks also
 
dmo said:
Is it this, or like this? http://i259.photobucket.com/albums/hh284/lpcapital/Cars/pic02.jpg
Click to expand...

Thats a different temperature sensor. It's called the oil/water temperature sensor but my guess is its in the oil :wink:

The one with the o ring that can fail sits in a hose coupling:

pic01.jpg

Probably in the radiator outlet hose near the radiator.

When searching for a leak its important that your system is pressurized, so with a hot running engine or with a pressure kit.
If there's no pressure, it wont leak.
 
GuidoK said:
dmo said:
Is it this, or like this? http://i259.photobucket.com/albums/hh284/lpcapital/Cars/pic02.jpg
Click to expand...

Thats a different temperature sensor. It's called the oil/water temperature sensor but my guess is its in the oil :wink:

The one with the o ring that can fail sits in a hose coupling:

pic01.jpg

Probably in the radiator outlet hose near the radiator.

When searching for a leak its important that your system is pressurized, so with a hot running engine or with a pressure kit.
If there's no pressure, it wont leak.
Click to expand...
Awesome pic. Thanks for the guidance. I'll have another look again today.
 
Mine doesn't look like that at all; is that a pic fro ma Z4C auto?

I think I can see some sensor, but it's impossible to access from above, even when you take off the little cover that covers the radiator and fan.

I ran it for 15 mins and took it for a 2 min drive, it looks like there may well be a leak but I can't for the life of me work out where it's coming from. All of the connections I can see and reach were all dry.

It looks like the biggest pool of water was immediately under the radiator/fan - are there any known leaks in that area?

The coolant temperature gauge didn't read high today, but tbh I wasn't pushing the car very much. If there's water leaking, does that rule out that the water pump is the problem?
 
Thinking to just buy this, in case it's the waterpump that's gone.

http://www.eurocarparts.com/ecp/c/BMW_Z4+Coupe_3.0_2006/p/car-parts/cooling/car-cooling-parts-and-car-heating/water-pump-gasket/

It's on offer; 30% off this weekend. Could someone confirm its the right part?
 
What is it? The link takes you to a page that just says "water pumps & gaskets" :?
Are you looking at the electric pumps?
Edit-just entered my car details & it shows the pump for £380, with the discount that's not so bad & its the oe parts supplier as well :thumbsup:
Through bmw they cost an arm&leg :thumbsdown:
Rob
 
Are you really going to drop £300 on something just in case that's the problem?
Without having any clue what the problem is?
Very bold. Or totally crazy.
Might as well take it into the stealers and let them rob you, coz it sounds like it'll be a whole lot cheaper than your current path.
 
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