Assuming a diesel engine is running smoothly, without any odd noises,
and handles well, is there any need for a compression test?
The local dealer was offering to do a pre-purchase inspection +
compression test for "only" $600.
He said it was a good idea to do it, as the car is nearly at 200,000
miles.
I know the engine runs well, and suspect it's not worth doing the
compression test, though the pre-purchase inspection would be something
I'm definitely considering.
I think he's just trying to get some money out of me. :/

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Peter W Peternouschek - 26 Aug 2005 08:35 GMT
The whole inspection thing for $ 600 smells like a major ripoff. Besides who
in his right mind would use a selling dealer do a pre purchase inspection.
If you absolutely need to do this, have an independent mechanic do it for
you.
Peter
> Assuming a diesel engine is running smoothly, without any odd noises,
> and handles well, is there any need for a compression test?
[quoted text clipped - 14 lines]
> Pete Stephenson
> HeyPete.com
Pete Stephenson - 26 Aug 2005 15:09 GMT
> The whole inspection thing for $ 600 smells like a major ripoff. Besides who
> in his right mind would use a selling dealer do a pre purchase inspection.
I agree, it does sound like a ripoff, hence my asking for confirmation
on if the compression testing is good or not.
I was calling around to various mechanics and dealers looking for who
would perform the most detailed inspection. If I could afford it, I'd
get it checked at a few places, but can't afford that.
> If you absolutely need to do this, have an independent mechanic do it for
> you.
Indeed. That's precisely what I have planned.
I take it that a compression test probably isn't necessary if the car's
running well?

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Cheesehead - 26 Aug 2005 17:40 GMT
My pre-purchase inspection, including mechanical and compression checks
(& perhaps leakdown, but I'm not certain) was a mere $20. And they're
a VERY reputable shop in Westerville, OH, that's done VW for 30 years.
Collin
Martin Joseph - 26 Aug 2005 18:09 GMT
> Assuming a diesel engine is running smoothly, without any odd noises,
> and handles well, is there any need for a compression test?
[quoted text clipped - 9 lines]
>
> I think he's just trying to get some money out of me. :/
Don't go to the stealership!
Find a local independant that know mercedes and go there. $150 Should
get you a good inspections and a compression test.
Even if the engine runs well, a compression test is a good idea IMO to
establish a baseline for any future issues, as the engine is new to you
at this junction.
Marty
T.G. Lambach - 26 Aug 2005 18:11 GMT
$600???
Call some independent M-B shops, ask their price for a compression test
and suspension inspection.
It won't be $600!
You now see why owners of out-of-warranty cars patronize independent M-B
shops.
It's your money. Good to know its well spent on a good car or not spent
on a car that will need more of your money.
cp - 27 Aug 2005 08:07 GMT
Here's a quick compression test IF the car still uses glow plugs to start: when the car is COLD try to start the car without waiting
for the glowplugs. If it starts it has very good compression (it will work rough for a bit), if it don't start... well, it just
means that it doesn't have very good compression. A 300SD I had started no problem with no glow plugs, it had a good battery of
course.
cp
> Assuming a diesel engine is running smoothly, without any odd noises,
> and handles well, is there any need for a compression test?
[quoted text clipped - 10 lines]
>
> I think he's just trying to get some money out of me. :/
Pete Stephenson - 27 Aug 2005 10:16 GMT
> Here's a quick compression test IF the car still uses glow plugs to
> start: when the car is COLD try to start the car without waiting for
> the glowplugs. If it starts it has very good compression (it will
> work rough for a bit), if it don't start... well, it just means that
> it doesn't have very good compression. A 300SD I had started no
> problem with no glow plugs, it had a good battery of course.
An excellent idea! A field-expedient compression test that costs nothing
would definitely be something to try.
The engine starts and sounds good when started with glowplugs, and had
good acceleration and handling on freeway onramps and at freeway speed.
I doubt there's a compression problem, but your field-expedient test is
something that would help me verify that everything's in good working
order without having to spend a boatload of money on official testing.
An inspection, yes, but compression testing sounds rather
expensive...this might just be the ticket.
Cheers!

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cp - 27 Aug 2005 20:45 GMT
>> Here's a quick compression test IF the car still uses glow plugs to
>> start: when the car is COLD try to start the car without waiting for
[quoted text clipped - 13 lines]
> An inspection, yes, but compression testing sounds rather
> expensive...this might just be the ticket.
Yeh, though I want to learn how to do a real compression test too :-)
cp
Martin Joseph - 28 Aug 2005 08:35 GMT
>> Here's a quick compression test IF the car still uses glow plugs to
>> start: when the car is COLD try to start the car without waiting for
[quoted text clipped - 13 lines]
> An inspection, yes, but compression testing sounds rather
> expensive...this might just be the ticket.
IT'S NOT EXPENSIVE TO COMPRESSION TEST YOUR VEHICLE. Sorry for the shouting.
The above "test" might be handy but teaches you very little about the
conditions of the engine internally. Temperature is also a big
variable in the above equation.
Try to find a local independant garage that knows mercedes cars and ask
about a a pre purchase inspection that includes a compression test.
It's worth doing, as in the future you can retest and KNOW if anything
has changed.
Marty
Pete Stephenson - 28 Aug 2005 17:47 GMT
> Try to find a local independant garage that knows mercedes cars and ask
> about a a pre purchase inspection that includes a compression test.
I've called three or four shops in the area and asked what they charge
for a pre-purchase inspection and/or compression test. We'll see.
> It's worth doing, as in the future you can retest and KNOW if anything
> has changed.
Good idea.
I'll probably end up doing the homebrew test, as well as the "real" one.

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