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Robert, UK Qualified Car Technician
Category: Car
Satisfied Customers: 4568
Experience:  Fully qualified / self employed garage technician in the UK
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My Mercedes C200 Elegance Auto 1998CC has a recurring petrol

Resolved Question:

My Mercedes C200 Elegance Auto 1998CC has a recurring petrol leak which happens when started after it has been sitting a few days. 3 garages can't find the leak as it never seems to happen when I leave it with them. One garage replaced the fuel filter. The car runs high when started then settles down after 1 minute. When it leaks the fuel drips like a tap and leaves a puddle and trails, then on one occasion, I then drove 250 miles with no leak at all. The car then has no leak for days. I would say this occurs mostly when the car has been lying a while. I would like to sort this as I don't want to lose the car. Kindest regards, Margaret.
Submitted: 3 years ago.
Category: Car
Expert:  Robert replied 3 years ago.



Hopefully i can help..


Do you know exactly where this leak - as and when it occurrs seems to leak out from under the car or rough area maybe?




Customer: replied 3 years ago.

Leak from protective cover just under the fuel pump and fuel filter at the rear of the car near the differential. No leak when car is not running only when first started. Then it is ok for days. Car runs high for a minute when first started no matter the weather. New fuel filter. Thanks.

Expert:  Robert replied 3 years ago.

Hi..there thanks for your reply..


Ok..Im not sure why when you do mention the leak is evident when first started they havent been able to pin it down.usually with any fuel leak it does need to be sorted especially with petrol..the standard practice really would be to leave the car over these period of days with that panel removed - then when its come to be started have somebody under the car observe and then turn the ignition to get the fuel pump running and prime the system and see where that leaks dropping from - .that would certainly give an idea where this is coming wither that been done as of yet or not - that could be something to try - as you'll know petrol does have a habit of evaproating fairly quickly which can make checkings for previous smaller leaks alot harder in some cases..if fuel is actually pooling on the under protection panel below that fuel pump/fuel filter..the its possible the problem maybe with the pump itself..but as and when the pump primes the system - then it should be noticable as fuel leaks dont tend to come and go as they please - they always crop up either when the system is under pressure or there is in fact one of the feed or return lines on the car is leaking maybe one of the solid lines may have corroded "which is quite common on these" and its generally a case really of tracing each line as you go - i know this may have already been done or not as you dont say - but that in reality is the way forward unless you go down the route of having the entire fuel/feed and return lines replaced - one other area i would maybe have look at or have looked at is the evap system evaporation emission control on that car this take the gases that builds up in the fuel tank and stores in a charcoal filter canister which i beleive is in the same area at the back until such time its released via small feed hose upto the inlet manifold to be burnt off so ensure that hasnt actually got petrol in it or has ingested neat petrol and the leak is coming from one of the vent hoses from the tnak to the canister/purge valve.certainly worth having that checked out.but as your description goes im kind of thinking this is more fuel line related.hard to say without actually doing proper tracking down and follwing the system/pipe routing around at the back.I do hope this helps..if you need to ask anything else or inlcude anything else then just continue before you rate

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Customer: replied 3 years ago.

Thanks for your suggestions so far. I will get these points checked as soon as I can and maybe have to get back to you but it may take a bit of time so until I have done so, thanks again for the moment.

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