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Discussion Starter · #1 ·
As you all know I my M5 was suffering from the dreaded "lorry" sound.

From last week it got alot worse and the car started running serioulsy hot to the point I just parked it up.

I solved this by taking out the rad and using a power jet washer to wash through it.

I cannt explain the amount of black **** and gung that came out from it. I sprayed through it from both sides for a good 15 mins and black stuff was still coming out.

After that the water turned clear and I could see through the rad.

The result:

Car runs so much cooler even sat in traffic for a good 20-30 mins. The temp gauge doesnt go past half, the oil temp stays where it should and the viscous only comes on for literally 3-5 seconds and then shuts up until I sit in traffic for ages.

This proceedure could save all of you ALOT of hassle with the coming hotter weather.
 

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I had the same problem, but I did not figure out that the radiator was filled with dirt until I overheated the engine on the German Autobahn in 250 Km/h. It did cost me a complete engine rebuild.
 

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that's strange, it would appear that the AC-condensor sitting in front of the
radiator would take most of the dirt, small stones etc. all that the 'kidney' is letting thru, i.e. the radiator still gets a lot of dirt and cud need cleaning ??
 

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Mine was _exactly_ the same, and the cause of all heat related problems - fixed with one jet wash (rad out of the car of course)

I would advise anyone with heat build-up problems to do this as a first port of call. 'Cheap as Chips' fix.
 

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M5touring reg said:
that's strange, it would appear that the AC-condensor sitting in front of the
radiator would take most of the dirt, small stones etc. all that the 'kidney' is letting thru, i.e. the radiator still gets a lot of dirt and cud need cleaning ??
The Viscous fn behind the rad blows into it so eventually you will get dirt buildup on the rad as and dust/dirt in the air will be blown into the rad by the viscous fan
 

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Also, I would be wary on bending the vanes on the rad with a power washer - I'd only use a regular hose and I'd try and soak it more as opposed to blasting it - if the vanes are bent / broken the rad will lose its efficiency and although it may run cooler initially, once you give it some on a track or get stuck in traffic too long it will be hotter, as the surface area exposed to the air will be reduced.
 

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I agree. Do not use a power wash. All you need to do is to soak it with a garden hose. The dirt will start to flow away after a short while.
I think that not only does the viscous fan pull dirt in, the electrical fan for the A/C pushes it in as well. Also, I guess that once the dirt has passed through the condesor of the A/C, the air speed is so slow that dirt will easily stick to the radiator.

Cheers. cherrsagai
 

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ilundber said:
I agree. Do not use a power wash. All you need to do is to soak it with a garden hose. The dirt will start to flow away after a short while.
I think that not only does the viscous fan pull dirt in, the electrical fan for the A/C pushes it in as well. Also, I guess that once the dirt has passed through the condesor of the A/C, the air speed is so slow that dirt will easily stick to the radiator.
Cheers. cherrsagai
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ok, I see (and learn every day), thanks !!
 

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M5touring reg said:
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ok, I see (and learn every day), thanks !!
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Ah ok, that is why my newer radiator does not allow the temperature to go over 40-45% in normal non city driving. I though it was calibrated wrong.

Great!
 

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Discussion Starter · #10 ·
As mentioned above, no need for power jet. The crud all comes out after a while but beware........do it somewhere you dont want the ground to get dirty as it will make a very big mess!
 
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