Mercedes ML270 engine temperature issue

[scotcruz]

Hi folks,

I have a 2002 Diesel Auto Mercedes ML270 which has developed a engine heating issue.

The temperature goes up at acceleration such as on motorways. When I lift the foot and speed goes below 60mph or below the temperature is fine. No warning lights..

I thought it was the thermostat so I replaced it but the issue remains.. Please can someone advise or have any thoughts what else I could check?

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[autoden]

radiator blocked partialy

[scotcruz]

Cheers mate.. what's the solution? Can it be flushed or is it time for a new radiator?

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[potrobber]

Does this have the fan blades mounted on the engine or is it a electric fan to cool the rads ? if its mounted on the engine it could be a faulty/worn viscous coupling.

Also the rad blocked as autoden has said is well worth checking, from cold start it and get car up to temp and feel the face of the rad in different places for cold patch's on the rad.

Another possibility is the water pump not circulating the coolant fast enough.

[autoden]

That radiator is now 13 years old, it would be my first job to replace it. If its ok below 60, but gets hot at higher speed, the airflow will be restricted so unable to cool the motor down. OR you could just drive slower and save on penalty points.:)

[scotcruz]

Thanks guys... Going to start with the radiator as suggested.. I hope its not the water pump..

Can radiators be flushed or you can only replace it?

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[potrobber]

Scot the rad can be blocked on the outside as well, ie with flys bugs midges and crap ect a good hot steam wash can clear them most times also connect a hose to the rad and run the hot steam thru the rad . if its not that expensive maybe just replace it or get a rad place to test it as some rads also cool auto trans fluid and you dont want to ruin a gearbox aswell is this your own car or someone elses?

Impellers can also come loose or corrode in the water pump making the blades smaller causing slower flow, is this problem something that's gradually gotten worse or just started all of a sudden?

Did you check to see if the cooling fan is elec or manual viscous coupling?