@i860 has some experience with lpg, perhaps he can weigh in.
LPG haters - please advise (post 62 & 80)
So, I took a day off today and went to the best Mercedes mechanic in Prague (judging by the reviews) because of that horrible rattling metallic noise that I have every time the tachometer needle touches the 2500rpm, every gear, both accelerating or slowing down, with or without gear, even revving with the car stopped.
As soon as his dog stopped chewing my leg, he took a look at the engine, saw the lpg system, and said: I'm not touching this car until the LPG is removed. You're destroying the car this way, Mercedes are not intended to be converted. When you install an lgp system in a Mercedes the engine head must be replaced with something compatible with this gas, and here it has not be done.
Now, I bought this car already converted, and given the price of the gas here, I don't mind paying a third. I wouldn't have done it myself, but it was there already, and I must admit it works pretty well.
He didn't say anything about the noise, didn't even want to listen to it, he went on for 20 minutes just cursing the LPG (I left, probably he's still going on).
My concern now is that I'll never be able to have a mechanic, because my car is converted... And yes, I tried the LPG shop, they said no, we only deal with lpg related problems, this noise is not related, go find a mechanic.
Do you really think I should have the system removed? Am I destroying the engine? Is it that bad? I just wanted to get rid of that rattling noise (not the engine supports, got them checked), I'm quite happy with having the option to save some money when I don't need to score the best lap time on qualifying session... But if it's really that bad, I can live without.
As soon as his dog stopped chewing my leg, he took a look at the engine, saw the lpg system, and said: I'm not touching this car until the LPG is removed. You're destroying the car this way, Mercedes are not intended to be converted. When you install an lgp system in a Mercedes the engine head must be replaced with something compatible with this gas, and here it has not be done.
Now, I bought this car already converted, and given the price of the gas here, I don't mind paying a third. I wouldn't have done it myself, but it was there already, and I must admit it works pretty well.
He didn't say anything about the noise, didn't even want to listen to it, he went on for 20 minutes just cursing the LPG (I left, probably he's still going on).
My concern now is that I'll never be able to have a mechanic, because my car is converted... And yes, I tried the LPG shop, they said no, we only deal with lpg related problems, this noise is not related, go find a mechanic.
Do you really think I should have the system removed? Am I destroying the engine? Is it that bad? I just wanted to get rid of that rattling noise (not the engine supports, got them checked), I'm quite happy with having the option to save some money when I don't need to score the best lap time on qualifying session... But if it's really that bad, I can live without.
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I know the older M111 engines had a pattern rattle due to wear in the camshaft adjuster - the way to check for it is to disconnect the harness from the camshaft adjuster... if the sound stops, you've found the source. I don't know if the same applies for the newer 4-cylinder engines though.
I'm trying to understand this. If you drive a car 20 miles/day, five days/week, 52 weeks/year, that's 52x5x20=5200 miles or ~260 gallons of fuel, at current prices at least $800/year USD. That's much more than you'll spend on oil, tires, brake pads, and all the usual wear items per year.Gas is the cheapest thing you put in a car.
@Bohemian TopDown I am just curious: is it easy to find LPG filling stations in your home town? I live in a fairly populous suburban area but the closest LPG filling station is a half-hour drive away.
If the noise subsides when in neutral then I would suspect the motor/transmission mounts.
Nobody is gonna listen if you post a link that asks for a password...
I have never heard a sound like that - but I'm not a mechanic. I know nothing about M271 engines and I don't have a wiring diagram or any literature about it... but I would use process of elimination to rule out the variable valve timing and the compressor bypass valve. You can probably unplug the camshaft magnets on the front of the engine long enough to rule them out - it might well set a code and turn on the check engine light, but it will rule them out. If the rattle stops, plug them back in one at a time and re-test to see which one is causing it.
I would likewise try to unplug the bypass valve just long enough to rule it out.
The sound does sound like it could be related to the compressor, have you checked all the ductwork?
I would likewise try to unplug the bypass valve just long enough to rule it out.
The sound does sound like it could be related to the compressor, have you checked all the ductwork?
1 - 7 of 84 Posts
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