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  #1  
Old 03-22-2006, 10:00 PM
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Compression test alternatives?

I got a recently purchased 1985 300td inspected by a mechanic at a mercedes dealership. There are have been some issues with the purchase (the car actually has about 350,000 miles rather than the 177,00 on the odometer), and I'm tryig to decide if the car is a good buy. The mechanic who did a "inspection for sale" for $95 (one hour). He was under the impression the car had 177,000 miles then and said that the the car was fine except for some minor suspension problems. I asked if he did any actual engine diagnostics and his answer seemed a little wishy washy. He said he did not perform a compression test but said that becasue the turbo was working that meant the turbo was working well. Is this true..a little..or not at all? Should I take this to another mechanic before I finalize the purchase. thanks for your help

Brett

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  #2  
Old 03-22-2006, 10:14 PM
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What are you gonna do if you find out it's got poor compression ?

If'n it starts/runs/very little smoke/burns little oil ( quart in 3K ).....drive it and stop worrying...
If the mileage is as high as you think....go find out about a timing chain replacement......shoulda had one by now though.


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  #3  
Old 03-22-2006, 10:19 PM
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I had heard that the compression is the most important thing to check as far as longterm engine wear. If the time chain hs not been changed would this lead to lasting negative effects on the engine after it had been replaced?
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Old 03-22-2006, 10:23 PM
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oh yeah, it does smoke a little when you accelerate heavily, but not when it starts or just in normal use, only heavy acceleration. I figure this is pretty normal.
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  #5  
Old 03-22-2006, 10:26 PM
t walgamuth's Avatar
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so if

he had not given it a clean bill of health would the purchase have been off?

and can you still get out of it if the compression test showed lots of wear?

and how did you find out it has 300k plus miles on it?

was it represented as having 177k on it?

if so you should be able to get out of the deal. and i prob would unless it was purchased very cheaply.

tom w
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Old 03-22-2006, 10:30 PM
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I found out about the cars actual mileage by reading through the service records that I found in the glovebox. I then did a carfax and it was confirmed. The seller was unaware (he had only had it for 10 months) of the mileage and offered to take the car back. He said he would give me a few days to make a decision about what I want to do. I paid 2400 for the car and it is in really great shape. I'm just a little concerned about how many more miles this engine has in it.
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  #7  
Old 03-22-2006, 10:56 PM
t walgamuth's Avatar
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i prob

would ask him to take the car back. it is not what you bargained for.

or if you really like it ask for $1000 back.

he has no ground to not take it back. it is too bad that he didnt know the truth (if he really didnt), but that is no reason for you to accept a car with twice the miles.

if it had a rebuilt motor with low miles that would be different.

at 3oo plus it is due for a head gasket if it hasnt been done and the tranny if not done will prob not last too much longer.

dont feel bad for him, do what is best for you.

tom w
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..I also have a 427 Cobra replica with an aluminum chassis.
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  #8  
Old 03-22-2006, 11:03 PM
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For a poor mans compression test do this:
How cold is it?
Skip glow plug cycle and see if she will fire.

I'd figure that a real tight 617 should light off stone cold with no glow plugs down to the mid 30's without to much trouble? Maybe colder? Certainly at 40-50 degrees she should light right off.
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  #9  
Old 03-22-2006, 11:32 PM
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Since this is disturbing you to some extent for the actual cost a second opinion may ease your mind. Overall it is a small expenditure really. Perhaps an independent firm non dealership but mercedes place may be around somewhere nearby? You should also be able to check out their reputation prior to the approach. Will at least make you feel better perhaps. Anyone on site really cannot offer a definative opinion as we have never seen the car and a small part of a purchase is kind of an intuative hunch when you see the car initially. I complete purchase on a car tomorrow that actually I paid a downpayment on last june. Agreement was the garage owner would get the title as the car had been left by a person driving through our area. Deal was to get an ownership from the government as there are new laws here when a car is intentially left at a garage. Took till this morning for him to get all the clearances and new ownership. The car again just in my opinion as it is not running was far too good to part out. Now the odometer says 159k miles. Not likely true but one never knows.The blind optimisim of hope thing again. Have been down this road so often it no longer bothers me. If true the cars a steal if not it is still basically a very good car from my perspective. Everything I could check out with a non running car I did..Almost seemed car had had a major going over for the trip it was on with money no particular object. My kind of previous owner. He was burning a mix of vegatable oil and diesel in january. Suspect car just gelled up and he burnt out the starter trying to restart. Unfortunatly the garage owner told him the injection pump may be bad before even changing the starter out and threw that into the quote. At first I thought the garage owner an unethical person. Found out he had changed four injection pumps out that were bad just previous to that cars arriving at his place on mercedes diesels burning alternative fuels. One could say he was reasonably biased? The local volkswagen people were also changing injection pumps like crazy.The local commercially available bio diesel was destroying pumps it turned out. So from the mechanics perspective it was a valid warning. Anyways the doctor went uptown purchased a new jetta diesel stationwagon and went on his way. The garage owner got the car for the flatbed charge of picking up the car from the highway and checking out that the starter was dead. His customer was located through information provided by the dealership that sold him the new volkswagen. The customer was given so long to settle up with the garage owner and remove his car. From the time frame to get all the official papers I presume he did not cooperate. My only concern is if the stuff he was burning in the injection pump has done anything funny in there as car has not run now for fourteen months. At worst I might have to change it out as well as install a starter. If the moisture content of his fuel was low I may be lucky and just have to flush out the injection pump. After the fun job of removing tank, cleaning it out and flushing the lines out of course. If not I have a selection of used pumps available through people that I have rubbed shoulders with that own them as well. What I am basically driving at is in my limited experience the buying experience on older mercedes diesels takes many turns in comparison to buying other cars. Insane does come to mind. After you buy about four to five of them it is something you adjust to. Or have your meds increased. A few days ago a guy phoned me that was selling three of them. I was able to easily discern that even if I had the space I did not want any of them. They did sound like excellent ebay material though. Four or five years ago I probably would have drove the forty miles and had a look. I just equate it all now as an almost continual learning experience. For no addition charge you seem to get an experience with ownership that no other car can provide Perhaps it's part of the allure. Too much information I know but I try to analyse why we do what we do. Or at least what I do.
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  #10  
Old 03-23-2006, 09:08 AM
krs krs is offline
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I'd be very concerned about a difference of nearly 200,000 miles on a car I'd bought. Even if there are a host of good points such as engine overhauled, trans. too, new front end and rear end tierod ends, bushings, and a rebuilt steering gear, - a long list of positives in other words, simple metal fatique becomes a very real factor in an old car.

I don't know how many here have experienced a car with so many miles that it's very frame flexes more easily than when new. One that "feels" tired no matter how much money is put into it in the hope of a rebirth. Even spotwelds begin to move and anything riveted enlarges the holes slightly. Every moving part from the hinges to the seat retractor gets worn and develops slop that wasn't designed to be. The metal parts change dimensionally - they stretch much as does skin on a woman's belly during childbirth and regain their shape with a similar unreliability.

Old cars feel old, and you've paid your money for a much younger car than you've received.

It's hard to imagine the PO being unaware of this considering that you were able to determine the fact of it from info contained right there in the glovebox.

Compression is critical in diesels. It's not all that uncommon for an old tired diesel engine to draw enough oil into the combustion chambers from the crankcase through worn rings to run on. I mean that the engine will continue to run after the driver has intended to turn it off because it's burning it's own lubricating oil for fuel. (Shutting off a diesel involves stopping the flow of fuel instead of turning off the electrical feed to the ignition system as in a gasoline powered vehicle)

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