Overheating & loss of coolant but no leak (solved)

[Robin82]

Hi forum members,

I cannot believe I’m yet again writing a post on an overheating issue with my zed. Finally got my z4 6 months ago after my old z3 eventually died due to multiple blown head gasket.. and now I’m having almost exactly the same symptoms!!

After a day out in the little sun we’ve had this year the engine started to overheat. Luckily I was only a short distance from home and arrived before it went anywhere near the red line. The coolant outlet hose had sheared off from the engine block so I replaced that thinking it was an easy fix. Obviously that was a symptom of a deeper issue as its still overheating.

Cool air out of the vents
No outward external leaks yet losing coolant
After engine up to temp steam coming from bleed screw and cap with Pipes extremely hot!

So I’m assuming the loss of coolant is due to the coolant boiling up and evaporating potentially due to it not circulating around the system?

Would point towards - broken water pump or thermostat?

Additionally the steam does not smell of exhaust fumes at all, there is no white smoke from exhaust or gunk under the engine cap! Thank the lord!!

 

[Chris_D]

Get a code reader on it buddy, see if anything comes up.

 

[Mr Tidy]

Reading the codes should tell you, but what engine do you have?

If it's a facelift that sounds like it might be the electric water pump.

 

[Robin82]

Get a code reader on it buddy, see if anything comes up.

I’ve just literally ordered Carly from Amazon as we speak! The apps £50 and device £61 but probably worth it considering they want £60 to plug a diagnostic in at the garage.

Reading the codes should tell you, but what engine do you have?

If it's a facelift that sounds like it might be the electric water pump.

It is a facelift! Its the 2007 2.0L N46 engine. Where is the pump situated in the bay? Is it much of a job to replace?

Cheers!

 

[Mr Tidy]

Well that's probably good news, as I don't think you have the (expensive) electric pump that the N52 engines have!

Sorry I can't help with it's location though, as I've only had N52s.

But I'd still want to get codes read before I started replacing anything just to be sure.

 

[Thrustyjust]

Did you bleed the system or just pour coolant in until it filled up ? Maybe just needing to be burped of air etc.

 

[Robin82]

Well that's probably good news, as I don't think you have the (expensive) electric pump that the N52 engines have!

Sorry I can't help with it's location though, as I've only had N52s.

But I'd still want to get codes read before I started replacing anything just to be sure.

Yeah certainly makes sense. Lets see what it throws up tomorrow..

Did you bleed the system or just pour coolant in until it filled up ? Maybe just needing to be burped of air etc.

I tried to bleed the system but as soon as the engine got up to temp it started to throw out A LOT of stream and lose coolant as a consequence. I guess there could be the mother of all air locks in the system preventing circulation.

 

[Mr Tidy]

But if you've had it 6 months and only recently suffered this problem how would the air have got in?

Good luck with tomorrow's diagnostic.

 

[dhobbs]

The coolant reservoir can get fine hairline cracks and loose water that way.
Also have you checked your oil for sludge? Hopefully not a blown head gasket

Old school technique is to fill up coolant, warm engine. Then switch off and cool down. Recheck again when cold and top up if necessary. Not done this on my Z4 but have done on older cars.

Good luck.

 

[Robin82]

I’ve now ran the Carly diagnostics and it has returned a report with the following:

Fault Code: 002F17
Fault Explanation: CDKMTOEL - forced operation EGS

Fault Code: 0000A5
Fault Explanation: :amplifier VANOS / Pressure sensor 1 are electrically defective / CDKENWSE - final stage inlet VANOS / internal index 100 / FT mirrors, potentiometer or horizontal lines / catalyst conversion / FUSE 30A / Fault lamp MIL OBDII fault !! / Fuse defective lamps

Fault Code: 006127
Fault Explanation: :Error code 27: steering angle does not satisfy
the test condition / error 27
Fault Code: 00611E
Fault Explanation: :Error Code 18: vehicle speed

Fault Code: 000041
Fault Explanation: :Car alarm: Inclination sensor / Short interior
lighting
Fault Code: 00000E
Fault Explanation: :COMMON. RELAY NO FAULT / HK: Physical or short circuit to U-Batt / Windows: interruption Einklemmschutzleiste or de-normalization / error EKS Electronic Beifahrertuer / Windows: interruption Einklemmschutzleiste Beifahrertuer

Most of these codes dont really throw anything up when searching online. I thought the engine fault might, but it doesnt seem to refer to anything. For £120 seems quite pointless!

In the mean time I have have noticed a weird ringing/buzzing noise coming from around the engine area as soon as I turn the ignition on before starting the car.

 

[Robin82]

Booked into the garage tomorrow morning as none the wiser after getting the fault codes read. I guess if its the pump or thermostat it would show anyway due to the pump not being electric.

Mechanic seems sure that its the thermostat due to a very hot top hose and cool bottom radiator hose. I’ll be re-trying to bleed the system today after another member had the same issue and solved it by bleeding. Apparently trapped air was preventing the thermostat opening.

 

[Robin82]

To update; took the zed out to a quiet country lane, parked it on a steep incline, nose up. I’d imagine most on here know the drill, although I did do something a little different as suggested by [ref]yg54sg[/ref] (cheers mate) Bought a 5L water bottle filled it with coolant and tipped the bottle right into the neck of the tank so that it created a sort of seal between the bottle and the cooling system. Which I assume helps create a kind of reverse plunger in that the weight of the bottle acts as an external pressure.

After the engine got up to temp my partner started take the revs up to about 3.5k, within about a minute a volcano of bubbles erupted into the bottle and the coolant started to disappear. Kept this up for around 10 mins. Lifted the bottle out and a further volcano of coolant followed with it all then settling down completely. Cap back on and a careful drive home.

Temp gauge remained at half way, and on the way home hot air started to flow out of the vents for the first time. :roll: Coolant light then came on numerous times I guess due to the system pressurising and sucking the coolant into the gap created by the large air lock. I was topping up a completely empty tank each time after the system repressurised, I’m sure it took another few litres of coolant at least.

Took it out for a good hour in the sun today and fingers crossed it looks as though it’s completely sorted.

Can you imagine the amount of water pumps, thermostats and all manner of things that have been needlessly replaced due to this issue?!

On the downside this issue has only intensified my car paranoia. Full service incoming.