overheats and engine cuts off

blazejzed

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r129/1992/sl500
hi i have a problem with my mercedes sl500 r129 1992 the problem is a really long story but the basics are that the engine gets to around 90 degrees and cuts off then it will not start straight away after this i have to wait around 1 hour for it to cool down and then it will start up and work no problem like brand new no engine cut offs. then ill leave the car parked up for another 4-5days or longer and the problem starts all over again also when i give it a kick down it will sometimes gulp before it goes to full power.
ps been to mercedes dealers and the best mechanics in town and they don't have a clue what the problem might be any help appreciated thanks.
 

turbopete

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2017 '17' Ford Mondeo 2.0TDCi ST Line X 180 (sorry)
sounds like a possible crankshaft sensor starting to fail, to me
 
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blazejzed

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thanks for that help mate will make sure to check it like i said nonone has yet solved the puzzle
 

brandwooddixon

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Agreed sounds like possible CPS issue.

I'm sure that Malcolm (Television) posted up in one thread the likely resistance when tested.

Either way, when the start to deteriorate there resistance drops as the heat up.

I think that they're not too expensive and easy to replace - there's a DIY thread for a different type of vehicle.

Sadly they don't always show up as faulty on STAR as fault codes are not always stored when they start to fail.
 

turbopete

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i remember the figure. the CPS should measure a max of approx 1k ohm (i believe up to around 1200 ohms is ok) and, when hot, they go open circuit, if the cps is the fault
 

television

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2002 SL500, 216 CL500, all fully loaded
Yes CPS on this one, they measure between 800 and 1k ohm when good and up to infinity when bad
 

brandwooddixon

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Ah, so I was wrong in stating that the resistance decreases.

Open circuit will mean infinite resistance on the multi-meter.

Thanks Pete.
 

television

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Ah, so I was wrong in stating that the resistance decreases.

Open circuit will mean infinite resistance on the multi-meter.

Thanks Pete.

Open circuit could be a better word, it is the construction, Iron core, copper wire all potted in plastic
 
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blazejzed

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distributor caps

hi thanks for all the help it wasnt cps sensor in the end as i have changed that before but it was the distributor caps they were rotten inside with a bit of fluid in too so i changed them job took me 40mins and all fixed.
 

rayhennig

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hi thanks for all the help it wasnt cps sensor in the end as i have changed that before but it was the distributor caps they were rotten inside with a bit of fluid in too so i changed them job took me 40mins and all fixed.

Great result. I've had the same myself.

I do hope you went for MB original parts or, failing that, Bosch or Beru. That goes for caps and rotors.

If you 'went cheapo', you'll be doing it again in a year or so.

Bonne chance.

RayH
 


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