Circulation pump open circuit

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Lulemmett

New Member
Joined
Dec 14, 2017
Messages
7
Location
Southampton
Car
E250
Hi guys,

New to this forum but hoping someone can help me with a problem with my 2010 e250 cdi.

My engine management light flashed up a few weeks ago so I took it in for a diagnostic. The code which was displaying is P260000 - the output for the circulation pump ‘coolant’ has an electrical fault or short circuit. The garage told me that it could be a fault with the aux coolant pump so I went ahead and changed it but this didn’t fix the problem. When I turn the ignition you can hear and feel the pump working so I have eliminated the possibility of the pump being faulty.

Another unusual thing I have noticed is sometimes when I remove the key and lock the doors the radiator fan continues to operate, tho it doesn’t spin at a constant speed it starts of slow and speeds up and continues this process until I turn the engine on and back off again.

Has anyone else experienced any problems similar to this. I have tried to find an answer but had no luck

Any advise is welcome, thanks.
 
Funny, thought i replied to this.
This is just a guess, but coolant sensor ?
Our Mini Cooper has a similar issue, fan running all the time, and for 10 mins when engine off, turned out was faulty temp sensor, changed sensor and cleared code, all good.
I suspect the sensor was telling ecu that engine overheating, hence fan coming on.
I know that the ML270 engine has a temp sensor in the thermostat housing, i do not know if yours is the same
 
Funny, thought i replied to this.
This is just a guess, but coolant sensor ?
Our Mini Cooper has a similar issue, fan running all the time, and for 10 mins when engine off, turned out was faulty temp sensor, changed sensor and cleared code, all good.
I suspect the sensor was telling ecu that engine overheating, hence fan coming on.
I know that the ML270 engine has a temp sensor in the thermostat housing, i do not know if yours is the same

THanks for your reply. You are right, you did reply to this already. I have posted it under engine and electrics as I am unsure the cause of the issue. You are the second person who has suggested the temp sensor, it certainly makes sense.

I haven’t had any issues with the engine overheating whilst driving, it has always had a running temp of about 80-90•c however I cannot speak for what the vehicle was doing when I was parked up.

Again you are correct the coolant temp sensor is located in the thermostat housing. I have seen another member who had the same problem on a C class so maybe they can shed some light on the issue but I think changing the sensor is my next step

Thanks
 
Its a good point you make about temp gauge, mini does not have one. I do not know if the sensor powers the gauge, or just engine electronics. Come to think of it, the Mini has two,one in the thermostat, and one in the head, so maybe the merc does as well, one for gauge, other for ECU. Im guessing
 
The main OM651 engine circulation pump is actuated by vacuum which in turn is electrically switched/controlled Perhaps the fault lies there? was your car diagnosed with the Mercedes Star diagnostic system?

Water pump failure
 
So a little update.

I decided that I would take the vehicle to Mercedes as I was starting to get fed up of replacing parts and not getting anywhere. After a diagnostic by one of their technicians I was told the fault was with the switch over valve. The fault code was current and stored and Apparently after changing the switch valve it was no longer stored, so I went and bought a new switchover valve, stuck it on the car and cleared the codes. 2 hours later the engine management light flashed back up and is now recording the same fault p260000

Any more ideas as I’m chasing my tail atm :(
 
The main OM651 engine circulation pump is actuated by vacuum which in turn is electrically switched/controlled Perhaps the fault lies there? was your car diagnosed with the Mercedes Star diagnostic system?

Water pump failure
My engine is M264 petrol turbo. It's a 2018 C300.
 

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