W202 has not much power when engine cooling fan comes on. Any ideas?

[Niks]

Hi Paul, im glad you posted this thread as I have a very similar problem too! Mine is a W124 and when the fan kicks in around after 90 (temp), I feel as if there is a loss in power from the engine, along with a heavy steering response.

When I start and drive the car in the mornings, it feels great. The engine is really responsive, give it a slight dab on the accelerator and it responds well, you can feel the torque. After around 5-10 mins worth of driving and when the temp reaches 85-90, the fan kicks in (makin the engine sound like a vacuum cleaner!), suddenly its not as responsive anymore, I feel less torque and I have to push my foot harder onto the accelerator to get any decent power. Then to top it off, the steering starts to feel kind of heavy and not as light as before.

Are you experiencing any of these same symptoms too?

 

[theonewhosmokes]

Hi Paul, im glad you posted this thread as I have a very similar problem too! Mine is a W124 and when the fan kicks in around after 90 (temp), I feel as if there is a loss in power from the engine, along with a heavy steering response.

When I start and drive the car in the mornings, it feels great. The engine is really responsive, give it a slight dab on the accelerator and it responds well, you can feel the torque. After around 5-10 mins worth of driving and when the temp reaches 85-90, the fan kicks in (makin the engine sound like a vacuum cleaner!), suddenly its not as responsive anymore, I feel less torque and I have to push my foot harder onto the accelerator to get any decent power. Then to top it off, the steering starts to feel kind of heavy and not as light as before.

Are you experiencing any of these same symptoms too?

Hi! The fan does certainly sound like a vacuum cleaner and I do need to press the accelerator further to get speed and the fan does come on about 85-90C. Sometimes my engine cuts out and is very embarrasing at roundabouts etc!!

I'm hoping someone here can help us both

 

[theonewhosmokes]

Here are the photos of my engine bay and of the fan.

I hope this helps....

 

[stevesey]

So do you think it could be a problem with the fan then?

Does seem unlikely - but your description says the poor running happens when the fan cuts in, just wondering if it's dragging the voltage down and affecting something. Simple check is to unplug and see if the fault changes.

Similarly have you tried disconnecting the MAF yet?

Is it an electric fan if not sure post a pic of the engine bay.

Switched from viscous to electric for 99MY.

 

[theonewhosmokes]

Does seem unlikely - but your description says the poor running happens when the fan cuts in, just wondering if it's dragging the voltage down and affecting something. Simple check is to unplug and see if the fault changes.

Similarly have you tried disconnecting the MAF yet?


Switched from viscous to electric for 99MY.

Is this the MAF in the photo below?

 

[KillerHERTZ]

Yes

Sorry to Hijack thread, my fan (same as above) never comes on unless the car is stationary & the aircon is on full for a while.

No problems to report - is this normal?

 

[theonewhosmokes]

Yes

Sorry to Hijack thread, my fan (same as above) never comes on unless the car is stationary & the aircon is on full for a while.

No problems to report - is this normal?

Thanks for clarifying that

Is it easy to disconnect?

Paul

 

[KillerHERTZ]

Just undo the metal tags from each side, then it should unclip with a firm but careful pull.

(I havent done it for a few years but im sure it wasnt difficult)

EDIT: Remove the plastic 'Mercedes-Benz' covering 1st, pull it off carefully - it wont break! and you will have better access.

+ Give your engine bay a clean aswell

 

[theonewhosmokes]

Just undo the metal tags from each side, then it should unclip with a firm but careful pull.

(I havent done it for a few years but im sure it wasnt difficult)

EDIT: Remove the plastic 'Mercedes-Benz' covering 1st, pull it off carefully - it wont break! and you will have better access.

+ Give your engine bay a clean aswell

So does the cover just pull of then?

Thanks for helping me - I really appreciate it

I have been meaning to get the engine steam cleaned as it is a bit dirty haha!!

 

[KillerHERTZ]

Left hand, hold under the very front middle left corner, right hand under the Z of Benz (top right).

Pull upwards, there are 3 big clips holding it in place. get an even pull from both hands and it wont break.

 

[KillerHERTZ]

From Steve Perrys thread:

Changing a M112 V6 MAS

 

[theonewhosmokes]

From Steve Perrys thread:

HERE

Thanks! Much appreciated!

I shall disconnect the MAF and see what happens.

Do you think the MAF is the problem when the fan comes on? The lack of power I get? It's like the air con is on, but it's not.

Paul

 

[theonewhosmokes]

Ok, so I unplugged the MAF/MAS and started the car. When I started it the fan came on and the temp was only between the 40 and the next marker - not at the 80 marker. I tried to take off and it was a little sluggish but better than before.

So, is the lack of power because the fan is using a lot of power? Or is there another problem?

I must admit, the car drove better with the MAF unplugged.

Please let me know what you think.

 

[lynall]

I think you need to measure the battery voltage whilst the fan is running and let us know the results.
Measure after standing all night, then when engine started, then when fan comes in.

Ps not sure why you have to remove the engine cover to either remove or unplug the maf.



Lynall

 

[stevesey]

So, is the lack of power because the fan is using a lot of power? Or is there another problem?

I must admit, the car drove better with the MAF unplugged.

I think you need to measure the battery voltage whilst the fan is running and let us know the results.
Measure after standing all night, then when engine started, then when fan comes in.

Then unplug the fan and measure.

Also measure the voltage directly across the battery and under the bonnet (terminal block behind the washer bottle to engine block). The differences will help highlight any earthing issues.

 

[lynall]

Good point about unplugging the fan and testing again but i thought as he never mentioned sluggish starting battery was okay, but you are quite right to check it as you never know.

Its always the obvious things that everyone overlooks, not me of course honest cough cough

Where is the battery on the 202 v6 back seat like mine or in the boot?

Lynall

 

[stevesey]

Where is the battery on the 202 v6 back seat like mine or in the boot?

Boot.

 

[theonewhosmokes]

Thank you both for your messages.

I think I need to take it to a mechanic as I really don't know what I'm doing with measuring voltages etc.

If you know someone good in the Ipswich area, I'll pay them a visit.

I do appreciate your help

Thanks

 

[KillerHERTZ]

Ps not sure why you have to remove the engine cover to either remove or unplug the maf.



Lynall

Easier to unplug with it removed.

 

[KillerHERTZ]

Ps not sure why you have to remove the engine cover to either remove or unplug the maf.



Lynall

Easier to unplug with it removed.

My C240 felt like its engine had doubled its bhp when I had a new MAF fitted...