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LPG haters - please advise (post 62 & 80)

2774 Views 83 Replies 23 Participants Last post by  Dave2302
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.
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Saying metallic noise, is it from the engine bay or under the car?
Gear Selector has a rubber, that I recently changed disgusting sound, that made me disassemble the cockpit more than once. If you are not sure what is checked, just raise the car on a platform/lift reach for the linkage between gearbox and shifter and make sure you shake it well. That bushing is 2GBP-2.5EUR let's say but the pleasure to replace it....

There is an example for the test, take the FUSE(s) of the lpg out - still the same - no LPG issue.
However inadequate LPG settings will lead to what i860 has covered.
SO, as a different approach, speak with a dyno test garage to check the car underneath (if possible of course) in 2500 rpms.
If they see a drop at 2500 rpms - that is serious.
If not, that would be every spinning component betweeen engine and exhaust - prop_shaft - has bearing, pulleys in the engine bay - bearings... they usually are audible in range, like 2000-2500 not only 2500, but who knows something very small could've keep exactly that frequency.
Can you make a video, like open your glove-box let the phone face up or down and start driving so the video gets that sound.
Someone can recognize it...
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Thanks mate, tomorrow I'll make the video and post. Hard to say where it comes from, seems like somewhere between the engine and the cockpit, more to the right side.
When I test it in neutral, it still does the noise, but much less, so it's difficult to find the source.
And of course, when I am with the mechanic it's the quietest car in the world, a Tesla basically. Left the car repair shop, a tractor again.
In the next days I will also go and ask how much it would be to remove the lpg system, just out of curiosity. Again, I am happy with it, but every time you visit a mechanic they treat you like you have the plague. Liquid PlaGue.
I wouldn't be bothered to remove the Liquid PlaGue (some sense of you humor you have) just to prove it ain't it.
But it will not hurt to check the fittings/holders/clamps....etc.
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And about the LPG, so far so good.
It has less power, true, let's say around 10% compared to standard fuel, but I can always press a button and go back to gasoline if I want to have "fun" .
But also let's be honest, the 200k is not that beast of power anyways...
10% is a bit too much, may be (just saying) you need to change the LPG filters and check the sparks?
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I think if you avoid garages and mechanics like this \/ \/ \/ and do your maintenance on time, as prescribed, you will not have many issues.

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What is a known fact, if LPG is fitted, the exhaust will need replacement sooner than expected.
My '96 accord had custom exhaust (as I took it, compared to OEM specs) but the flexible under the engine connecting the pipework with exhaust manifolds lasted 2 years, the last box 3 years, after I got it. No one could say how old they were, but for the next 3 years no exhaust leaks were found and it went to another owner.
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... a spark from the Courtesy Lights Switch...
Now you know why everything is off in my vehicles!
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