Inspection Checklist for buying older Mercedes diesels

[Kamel]

This is NONE of my own work basically, just ideas posted (and many times directly quoted) from other people. My goal here is to come up with a complete inspection checklist for an older Mercedes diesel car. I do not know the validity of the checks listed, but would like to expand this checklist so if anyone would like to add to it or take away, post a reply with your input and I will edit it accordingly.

Ideally, there will be 2 parts to the checklist. First, the things to check, then the next list is what those things mean, or even details about it (if applicable). For instance Checklist 1: 3) Check how long it takes the vehicle to start from being cold. Checklist 2: 3) A good engine should start within 3 seconds first try, if it doesn't it may need rebuilt to fix lost compression. Note: totally bogus example. Anyway, here goes my raw checklist, perhaps I could improve it with suggestions and it can be a good resource for the members of this forum .

Checklist 1:

cold start ability

check for smooth idle

check oil pressure gauge (should be maxed when accelerating and cold idling, about 2/3 up when warm idling) (At idle, I prefer the minimum oil-pressure to stay above 1-bar or 15 psi and the oil pressure reading should rise quickly to maximum once the car gets moving.)

transmission (a) - check for smooth firm shifting, but not rough

wagon - check rear end suspension for being too bouncy or saggy, may indicate problem with self leveling suspension

no green anti-freeze (thermostat danger; somewhat debatable)

clean brake fluid, brown indicates calipers may freeze up (relatively inexpensive fix)

check under the floor pan carpets, inspect door seals, hood and trunk seals. look for moisture/water/rust

check drainage spots, hood, sunroof, rear drains in trunk

check out suspension bushings for dry-rot. determine how bad the dry rot is and if replacement is necessary

check out steering damper/idle arm bushings/front suspension

look for leaks on the engine itself

check transmission fluid color - black = no good, very poor maintenance.

check under seats, near door frames for rust and soft spots. check under carpet

check battery try for rust through, check if it is on the firewall/fenders.

check upper and lower control arm bushings with flashlight. upper is easy to change, lower is expensive/difficult. if there is cracking or gaps in the rubber it will need replacing soon.

look over the rear end CV boots, cracks are normal, but a sign that it's due new axles. cracked and leaking or taped... definitely needs new axles.

look at drive shaft, the front and rear connectors are called flex disks, age cracks forming? if so must be changed. while there, inspect center bearing.

when test driving, the steering should be crisp and the handling tight. if it's loose, or squeeks, repair is necessary.

start it cold. don't give the glow plugs time to heat up, just start cranking. does it start? how long of cranking did it take? when it starts is it lopey or rough? turn it back off and this time let the glow plugs warm for 35 seconds. crank it again, start smooth?

when it's running pop the hood and pull the oil cap off to check for blow-by. place the cap loosely on the slot and see how much it rattles/perculates.

check door sill around seatbelt, verify that there isn't rust on the lower seatbelt anchor.

Check engine oil, see color/consistency. Is it gritty? Any engine grime?

Removed:

remove the air breather tube from the air filter and block it off. An ok engine will run for about 5 or 10 seconds... a good one runs for 20 to 30 seconds. A bad engine stops between 3 and 4 seconds. Then cut the engine, open the air filter and check for excessive oil. And last but not least, check out the heater fan etc... If it doesn't work, walk away..It's probably not worth the effort.
*Removed because You can blow engine seals or seating rings by creating excess pressure in the crankcase

Yea, I know it needs work =\. I haven't done any second checklist like I suggested, perhaps it isn't necessary though. BTW, Please let me know if such a thing exists so I am not 'reinventing the wheel'. Thanks

[UriahT]

I think this is a great idea for new Mercedes Diesel buyers.

Great start. This could be a great pictorial with pictures and/or culled from the archives- ie. what a lot of blowby looks like vs. minimal, or transmission fluid colors (new vs. old).

I would add more about A/C or Climate Control functionality also- does the compressor kick in, is it noisy, does the ACC turn on on all settings or does it need defrost to kickstart, etc. Also check functionality of vacuum related components- does car turn off right away, are brakes hard, do door locks hold charge for an extended period.

I believe ALL new buyers should own a Mityvac and small metric toolkit for just checking out the cars.


Just noticed this:
remove the air breather tube from the air filter and block it off. An ok engine will run for about 5 or 10 seconds... a good one runs for 20 to 30 seconds. A bad engine stops between 3 and 4 seconds. Then cut the engine, open the air filter and check for excessive oil.
Not advisable. You can blow engine seals or seating rings by creating excess pressure in the crankcase.

[Kamel]

Thanks for your input, I'll edit the post accordingly .

Glad you like the idea, I think it would be an excellent resource. Adding pictures would be very very valuable for some of these things, and video for some as well (such as blow-by, what's excessive and what's normal)

[Kamel]

Shameless bump. Common' guys, I really think this is a good idea we can all collaborate and put our minds together and accomplish. The amount of posts it prevent people from asking in itself would be worth the effort required to make it.

[barry123400]

These items are a good ideal for a preliminary look. If things look pretty good Try to find someone that is really familiar with the type to go as well. Especially if you have never owned an example before.

Their objective and knowledgeable input can really help. Barring that the car should go to an independant mercedes service shop for a real hard lookover. Again one that is very familar with that model. You really do want to know what exactly you are getting into.

Either one of those options should be enough to eliminate the rose colored glasses effect a purchaser sometimes has.