Before doing anything else, you need to go through a quick inspection 10-point checklist. Here goes:

1. Check for excess oil in the air filter housing. Remove the filter housing and check for oil on the filter and in the bottom of the housing. It is common to see some oil in these older engines, but it is not good if the filter is drenched in oil and/or you see standing oil puddles in the bottom of the housing. That would be a sign that the engine has excessive "blow-by".

2. Blow-by test A. This is a followup to the preceding visual test. Start the engine and let it idle. Loosen up the oil filler cap on top the valve cover and let it just rest over the hole. Observe what it is doing. If it is hardly moving, that is a good sign. If it is "jumping" all over trying to fly off, that indicates lots of blow-by.

3. Blow-by test B. This one is not particularly grounded in science but it can provide another "reading" on your engine health. You will want to put some gloves on for this one. Sit can be a little messy. Unhook the breather tube where it attaches to the top of the valve cover. Start the engine and observe. Do you see lots of fumes blowing out the hole? After a minute or so, do you see an oil film start to form on your finger? Now take your thumb and plug the hole. Start counting seconds to see how long it takes before the engine shuts off. If it shuts of in six to ten seconds that is the "normal" range. I have seen really good engines to 20 to 30 seconds before quitting and "bad" engines quit in 2 to 3 seconds.

4. Check the condition of the camshaft. With the oil filler cap off, you can look down on the camshaft. I use a flashlight and also put my finger in the hole to "feel" the camshaft. If the lobes are smooth, that's great, but if they are scored or rough feeling in any way, that most likely means the maintenance has been neglected. Lack of frequent oil changes will show up here.

5. Oil pressure at hot engine idle. SYou have to make sure the engine is really hot to get an adequate reading. don't just start and run it. Take it out on the road for a 10 minute test drive. Now, observe the oil pressure gauge. There are two things you are looking for. How low does the reading get? How quick does it peg-out when engine rpm is increased? Your oil gauge will either read 1 - 2 - 3 milibars or 15 - 30 - 45 pounds. Although I would not like personally to see my pressure go below 1 milibar or 15 pounds, Mercedes says acceptable low readings can be .5 milibars or 7 pounds. (Remember, this would be at hot engine idle with the transmission in gear and the vehicle stopped). Now, push lightly on the throttle pedal and as engine speed increases, watch the oil pressure gauge reading.

by the tie engine speed reaches 1000 to 1200 rmp, the oil pressure gauge should "peg-out" at 3 milibars or 45 pounds. If you get to 1500 rpm and the oil pressure is still not pegged, you probably have a serious problem. It most likely would mean one or more of the engine's connecting rod bearings are badly worn or scored. There is always the possibility you could have a faulty oil pressure gauge but that is very unlikely.

6. Fluid leaks: If there are a lot of oil leaks "all over the place," it is a sign the engine has not been cared for. Of course, there is really no quick way to check for the leaks. In order to track down the leaks, you will need to do a thorough cleaning of your engine (front and bottom) with gunk and a trip to the local car wash. Most older diesel do drip a little bit of oil here and there, but it should not be a major concern. If your oil drip spot (s) dte beigger than 6" in diameter on the ground, then you should probably go after the source of the leak.

7. Visusal check of injectors: take the "number 1" injector out of the engine for a good visual inspection. Look down into the pre-chamber. There should be a light, brown color. If there is a lot of black oil in there, you have oil pumping by the rings. If it is full of black soot, you are not getting a good burn on the fuel and this can be caused by incorrect injection pump timing or worn out injectors themselves. Now clean off the bottom of the injector with a brass wire brush. Take a close look at the area right around the needle. If it is perfectly flat and smooth, then your injectors may be ok. If there is a dished-in area around the tip of the needle, your injectors are worn-out and they are leaking at the tip and causing excess heat burn in that area.

8. starting sequence hot or cold: This is the one I like. It takes a little experience but when you have been around Mercedes diesels a while, you can tell a lot about their health by the way they start. How fast does it fire-off when cold? If the glow circuit seems to be working properly, it should fire right off and run smoothly. If it coughs and sputters and you have to crank for a while, there is a very good chance the compressiion is weak. If it starts right away but runs a little rought for a while, it just may be one or two bad or tired glow plugs. Also, how does it start when hot? You should not even have to wait to "glow" the engine when hot. If you get in the car and just start immediately cranking and the engine fires right off, that is a good sign.

9. Visual look and smell of fuel: You can not believe that number of diesels being dumped because they have been diagnosed termilly ill by some mechanics. Only to be discovered by new owners to have bad or incorrect fuel in the tanks. With bad fuel, ykou get all the signs of a worn out engine, like hard starting, rough idling, smoking, poor fuel economy, and lack of power. When you have bought a mercedes diesel that you know nothing about, I suggest you drain the tank, change the pre-filter and the main filter. Then go by the local truck stop and get yourself five gallons of fresh fuel, put it in your tank, purge the air out and drive back to the truck stoop and filler up. Always buy your fuel from truck stops if possible. they get fresh fuel daily.

10. Engine shut down: The way a diesel engine shuts off can also be another test for its condition. If it shuts off abrubtly, that is good. It means the vacuum system is working properly, the motor mounts are intack and it has good, strong compression. If it shuts off slowly and does not stop with a good "kick", it may mean problems with the vacuum shut-off and possibly poor compression. You will also want to listen closely when you shut it off. If you hear any clunking noises, your motor mounts are most likely bad and need replacing.

Another thing about shuting off. If your engine does not shut off at all. you should chect the vacuum shut-off valve before condemning it. Look on the rear of the injection pump near the fire-wall end of it. You will see a brown hard vacuum line coming from the firewall and going down to the shut-off valve. Disconnect the line and connect a hand-held vacuum pump to it. Next, start the engine and then go give the vacuum pump a couple of trigger-pulls. If the engine shuts off, you know that the shut-off valve is ok and you have a vacuum problem somewhere.

Well, thats it for now. If you have any additional questions, give me a hollow at my email address.

alfredburn@hotmail.com

Peace out.