New to Diesel, Some Questions
 

Just took delivery on a single owner 1985 300CD with 244k miles and complete service records. I spent a few hours cleaning up the engine bay. Having never owned a diesel before I am perplexed by some of the routine things people do at this mileage. Based on videos from the gentleman in Bellingham Washington it seems like I am looking at:

1. Adjust valves
2. Verify good compression
3. Replace the timing chain, it has never been done
4. Rebuild the turbo
5. The trap oxidizer was replaced by dealer in 1991. Does this mean they replaced it was something that does not need to be cleaned out, or did they use an updated trap that is likely to be clogged today? Will a standard trap bypass fit the new trap device installed by the dealer?

Does this seem reasonable?

Check and adjust valve clearance once a year. Before it gets cold if it gets cold where you are.

I wouldn’t bother with a compression test if it starts easily, idles smoothly and has decent power.

I wouldn’t replace the chain if it’s within a couple of three degrees of spec using the eyeball method. Check whether it has an offset key.

I wouldn’t rebuild the turbo if the engine performs. Any axial play in the turbo shaft is bad. Anything more than just perceptible radial play is bad. Any oil leaking into the compressor or turbine sections is bad. I don’t know if crankcase ventilation dumps upstream of the turbo so confirm the source if you see oil on the compressor wheel.

IIRC the 617 trap warranty replaces it once. There’s no servicing a trap. An alternative to a trap bypass is retrofitting the manifolds, turbo, downpipe and air cleaner from a pre-trap 617. You can keep the air cleaner where it is with minor modification of the turbo air inlet hose.

Sixto
98 E320s sedan and wagon
02 C320 wagon

Did they use traps on the 617? I would have said no.

Yes, they did. The 1985 California models have them.

To the OP: Originally the trap oxidizer was supposed to be changed out periodically as part of the service for the California models; every 35,000 miles is possible but it has been a long time since I thought/read about it. Sometime in the mid-1990s there was a campaign to replace at no charge the trap oxidizer with a trap catalyst which is supposed to be a "lifetime" item. My letter about the campaign is dated sometime in 1995, I think. Unlike the 603 motors, the trap cat for a 617 looks pretty much exactly like the trap ox. I'd call the nearest dealer, give them your VIN, and see if the trap ox was ever replaced with the trap cat. Also, the trap cat is not supposed to get clogged (or worse disintegrate) but people have posted on this forum about both of those things happening. It's worth looking into. There are several suppliers of straight pipes that replace the trap cat that might be worth investigating. I believe they involve replacing the dealer fitted device all together. FWIW, my '85 300D with ~300,000 miles is still wearing the trap cat that was fitted in 1995 and it seems to run okay.

Congratulations on your purchase, it sounds like a nice car.

The trick to running an old diesel without busting the bank is to not fix what isn't broke. Valves need to be adjusted. I like to replace all the rubber vacuum connectors under the hood because they deteriorate fairly quickly. Change fluid and filters. And then wait for the car to tell you what it needs.

Probably some of the best advice I've seen on this forum. Something about these cars make me obsessive/compulsive about every little thing.

How about some pics of your "new to you" ride?

replace the driveshaft flex disk,check boot,on rear axles

This is one train of thought that I like in theory but have a hard time living by.

Reason being is that typically at this age most of the rubber components / hoses/ and belts (unless you have documentation of otherwise) are typically due for replacement.

I think you can get many trouble free miles from a diesel with fresh fuel hoses and filters, coolant, thermostat, and hoses, new drive belts, and all new vacuum lines.

It is also good measure to just replace the flex discs and driveline center bushing/bearing.

I like to attack suspension clunks as they come up and try to only repair what is needed since I find the original MB parts to be of much higher quality than new replacements.

IF/WHEN you replace the glow plugs is a good time to do a compression test. If it starts and runs fine, don't look for trouble.

My self? The first thing I check on an unknown engine is valve adjustment and compression but that is just me. I want to know what I am dealing with and I also have all the equipment required. It's no big thing for me to pull the injectors, pop test them, replace the heat shields and install new fuel return lines.

I suggest running a good cetane booster with every tank of fuel. These old diesels perform better with a little extra bit of "oomph" to compensate for the ULSDF we get at the pumps.

I use the Stanadyne brand but there are many others available.

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