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1981 Mercedes 300D
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Discussion Starter #1 (Edited)
I noticed that the engine on my 300D started to get a bit noisier after its first fill-up here in Alaska just last month. With winter here, I'm assuming that it's a winter blend of some sort.

Anyway, I happened to have a can of Diesel Purge laying around - so I decided to give it a whirl on my car. I'm a bit skeptical being that the can says it's mostly diesel fuel mixed with what I would guess is snake oil.

I took a couple of short video clips with my camera and posted them here:
YouTube - AKJeeper's Channel

Check the vids out. I wasn't just hearing things - the engine really did get quieter once it was running on the purge.

I drove the car after changing the fuel filters, and sure enough, it even felt a bit smoother. There wasn't really a change in the 0-60 time, though. DP is definitely not a hotrod-in-a-can as some people on these forums sometimes claim. ;)

Over the weekend, I put on 200 miles. The engine is still smoother than it was, though the engine is just a tad noisier than it was prior to the "purge". DP still seems to be mysterious snake oil to me, but I can't deny that it has done "something" to quiet down and smooth out my engine.

I'm thinking the engine could use some new injector nozzles (I'm thinking of using Bosio?) and the injectors pop tested and calibrated. I'll wait until summer, as you can see in the video - it was quite miserable out there! :)

Any thoughts, comments, or suggestions are greatly encouraged, and appreciated!
 

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W-1-2-3 Go!
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16,161 Posts
Hi Darren,

The effectiveness of DP depends on how worn the engine is. When I did it on mine I did not notice any significant decrease in noise. The noise was decreased when I had a valve adjustment done, however. But using DP helped as the engine felt lighter.

I guess the three best things you can do to these cars are using DP, a valve adjustment and giving it a good oil change.

Just one question though, did you use DP when the engine was already warmed up? When it's cold it's almost always noisier, with or without DP.
 

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1981 Mercedes 300D
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1,249 Posts
Discussion Starter #3
I forgot to mention that I drove the car around for about 2 hours prior to doing the purge. So yes, the engine was plenty warm (175*F) when I took the "before" video.

I did the valve adjustment last weekend, same day I installed the block heater. Most of the valves were still within spec from when I adjusted them (summer '06), which I suspected since the car started up just fine even in single-digit temps. The block heater was a PITA to install, I ended up removing the intake/exhaust manifolds for better access.

The car ran great (albeit a bit noisy with winter fuel) prior to DP, though it does seem a bit more responsive (though no faster) after DP. You can even hear the engine's responsiveness in the videos. I'm running synthetic oil (Valvoline Premium Blue Extreme 5w40) to aid with winter starts.




Hi Darren,

The effectiveness of DP depends on how worn the engine is. When I did it on mine I did not notice any significant decrease in noise. The noise was decreased when I had a valve adjustment done, however. But using DP helped as the engine felt lighter.

I guess the three best things you can do to these cars are using DP, a valve adjustment and giving it a good oil change.

Just one question though, did you use DP when the engine was already warmed up? When it's cold it's almost always noisier, with or without DP.
 

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2013 MINI Copper S Clubman, '84 300CD-weekend car
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10,152 Posts
Glad to hear things seem smoother. The purges I do, I can't tell any difference, but do one when I pick up a diesel.
I would wait for the test on the nozzles before ordering something you may not need.
 

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1982 300TDT 150,000 miles 1985 380SE 130,000 miles 1991 560SEL 81,000 miles (a/k/a the nightmare)
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1,993 Posts
It definitely sounds quieter after the purge, IQ.

BTW, what did you fill the new fuel filter with before installing it, and how long had the previous main fuel filter been in operation... and how about your prefilter?

I found that changing the prefilter every other oil change creates miracles of its own.

How's your cam and IP timing. Everything I've read leads me to the conclusion that when you swap injectors, you need to make sure they 'pop' at the same pressures and those pressures are within spec... some people have had bad luck with Bosch products as of late, and prefer Bosio parts for rebuilds... anyway, when you change the injectors, since they pop much better, you should change the timing chain/adjust it at minimum, and reset IP timing.

The reason, partly, that our engines are so long lived is that our injectors pop 'less' as the timing chain stretches, thus putting less strain on the engine to deliver more power when cam timing slides off... Not a very technical explanation, but a good one nonetheless.

If your car has about 200K on it, I'd just as soon install a new chain, tensioner, cogs, and guides... some people say that you can run the factory chain indefinitely by adjusting with woodruff keys, but being as you're in extreme weather conditions now, it's probably best to change those parts rather than adjust... relatively cheap insurance. Extreme weather or not, as soon as my cam reaches 4* retard, I'm doing the works...

When I put the antigel/cetane boost in the tank, my car is much noisier than when I run straight diesel...
 

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1981 Mercedes 300D
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Discussion Starter #6
After I did the purge, I filled the new fuel filter with diesel. I didn't even think to pour the remaining DP in the filter (doh!) and poured it in the tank instead.

The last fuel filter was installed sometime during the summer of '06 at 206k. The car was pretty much parked in storage back then, only to be used when I was vacationing in California. I'd usually put a lot of miles on it (sometimes as high as 3k) when I did use it, so it almost always got completely serviced whenever I'd use it on vacation.

I looked at the cam when I did the valve adjustment last week. It didn't have any unusual wear marks on it. The cam lobes still looked nice and round (no flat spots). I didn't take any measurements, but simply assumed that it's probably ok judging from the wear (or lack of) marks.

I checked for chain stretch when I replaced the oil pump a few weeks ago (after fixing the engine's problem of losing all oil pressure), and it is just a touch past the 0* mark, at what I would eyeball as approx. 2* retarded. I repeated the cam stretch test two more times just to be sure. Do you think I need to change the chain with as little stretch as it has? The cog on the camshaft still looked quite good, it didn't have any sharply pointed edges on the teeth (an indication that it has worn out) where it 'hooks up' to the chain.

As far as IP timing is concerned, I still have yet to get the 'drip test' tool. So I don't know where the timing on my car sits. I'm trying to look into those diesel timing light adapters as an alternative to the drip test method, sounds like it could make timing checks a snap!

I talked to a friend with a diesel Superduty, and he said his truck regularly gets noisier when the gas stations change over to winter blend diesel. I'll have to see how my car sounds once it's back on regular diesel. :)




It definitely sounds quieter after the purge, IQ.

BTW, what did you fill the new fuel filter with before installing it, and how long had the previous main fuel filter been in operation... and how about your prefilter?

I found that changing the prefilter every other oil change creates miracles of its own.

How's your cam and IP timing. Everything I've read leads me to the conclusion that when you swap injectors, you need to make sure they 'pop' at the same pressures and those pressures are within spec... some people have had bad luck with Bosch products as of late, and prefer Bosio parts for rebuilds... anyway, when you change the injectors, since they pop much better, you should change the timing chain/adjust it at minimum, and reset IP timing.

The reason, partly, that our engines are so long lived is that our injectors pop 'less' as the timing chain stretches, thus putting less strain on the engine to deliver more power when cam timing slides off... Not a very technical explanation, but a good one nonetheless.

If your car has about 200K on it, I'd just as soon install a new chain, tensioner, cogs, and guides... some people say that you can run the factory chain indefinitely by adjusting with woodruff keys, but being as you're in extreme weather conditions now, it's probably best to change those parts rather than adjust... relatively cheap insurance. Extreme weather or not, as soon as my cam reaches 4* retard, I'm doing the works...

When I put the antigel/cetane boost in the tank, my car is much noisier than when I run straight diesel...
 

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Registered
1982 300TDT 150,000 miles 1985 380SE 130,000 miles 1991 560SEL 81,000 miles (a/k/a the nightmare)
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1,993 Posts
Some people cay you can run the factory chain for eons in this car by just using woodruff keys (they come in up to 10* adjustment keys IIRC)... At 2*, no, there should be no need to change the timing chain (do you have a woodruff key installed?)... in my wagon, I plan to have the chain swapped out at 4*, etc. Again, I wouldn't go just willy nilly changing things out, but I know that chain tensioners sometimes like being swapped out after having been sitting installed for numbers of years. Take a look at the cogs, and if it's good, let it be... no need to go crazy... I have no idea how often they would need tending to in a diesel.

You're doing a good job monitoring things in the engine... just continue doing it every time you adjust your valves. It's hard to get an answer from MB has to how often they would like you to change the chain in our vintage diesel engines, but every 200K would probably do nicely... My experience extends more towards maintenance of MB gassers, which require a new chain and stuff every 100k or so... I'm sure many issues are very similar for the diesel, but of course, intervals are different.

Just check that tensioner and the chain rails while you're at it, and you're good to go. You can adjust that retard out of the chain with a woodruff key if you're so inclined, and set IP timing when you swap out injectors... though there are different ways of going about getting things all where you want them when you swap out injectors, that's just what I'd probably do in your case. But, then again, you seem to be pretty knowledgeable, unlike myself, so you might opt for one of the other paths... I try to make things as easy as possible for myself (in some ways when it comes to these cars) as I am just learning about engines.

For instance, I've read that you can adjust the IP timing at any point, since it's so easy to do... let's say you adjust it every time you adjust your valves. Then your chain and IP are in 'Harmony.' just swap out your injectors at that point, and you should be good to go... I have no idea, however, how that would fit into the mechanical argument for the longevity of our engines (i.e. less powerful popping injectors as chain stretches)... That's why I suggested doing a clean sweep of tings that need to be tended to when you do swap them out..

In any case, if you come across better info in your searches, I would be obliged if you let me know, as I'd like some clear answers to this as well for when I'm ready to tackle the same thing myself...

My chief concern here is not stuff like the cogs, tensioner and rails, which can be easily monitored and inspected, but the nature of the chain while it stretches to different lengths...
 

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1981 Mercedes 300D
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Discussion Starter #8
I have no idea if an offset woodruff key has been installed on my cam. If I were to guess, I'd say no - it doesn't look like the camshaft bolt had ever been removed. It didn't seem to have the telltale marks on the bolt head to indicate that someone had put a socket or wrench on it, anyway...

I've had an engine destroy itself early in my driving career because of a failed timing chain, so I'm a bit paranoid about them. I may end up replacing the chain this summer, if I can get someone to give me a hand with it. I haven't done a chain replacement on these engines (MB engines are new to me as well), but I heard it is imperative that the chain is held TIGHT as you are threading the new chain in. Otherwise, the chain could to skip a tooth inside the engine, which would throw off injector pump timing, and you'd pretty much have to strip down the engine to fix that. That's what I've heard, anyway. I'm not about to tackle this single-handedly, I'll need someone else around (preferrably mechanically inclined) so that we can be sure the new chain feeds in properly.

I may forgo the offset woodruff key being that mine is only 2* retarded. Instead, I may just purchase one of those diesel timing light adapters and (hopefully) set the IP timing that way. I'll definitely keep everyone posted when I do decide to fix/check the IP timing.

As for the injectors, there are times that I wish I lived someplace other than Kodiak, AK. I don't know of any place locally that can pop test and calibrate the injectors. I may opt to buy some pop tested and calibrated injectors that have already had Bosio nozzles installed. Additionally, I may remove the injectors from a '79 300TD at our local wrecking yard and have those rebuilt with Bosios, as an alternative. Basically, I'd just like to minimize down time as much as possible.

I really appreciate all the responses I've gotten since I've joined this forum. You guys have been a great resource, and it's great to share my own experiences with you all too! :)

Some people cay you can run the factory chain for eons in this car by just using woodruff keys (they come in up to 10* adjustment keys IIRC)... At 2*, no, there should be no need to change the timing chain (do you have a woodruff key installed?)... in my wagon, I plan to have the chain swapped out at 4*, etc. Again, I wouldn't go just willy nilly changing things out, but I know that chain tensioners sometimes like being swapped out after having been sitting installed for numbers of years. Take a look at the cogs, and if it's good, let it be... no need to go crazy... I have no idea how often they would need tending to in a diesel.

You're doing a good job monitoring things in the engine... just continue doing it every time you adjust your valves. It's hard to get an answer from MB has to how often they would like you to change the chain in our vintage diesel engines, but every 200K would probably do nicely... My experience extends more towards maintenance of MB gassers, which require a new chain and stuff every 100k or so... I'm sure many issues are very similar for the diesel, but of course, intervals are different.

Just check that tensioner and the chain rails while you're at it, and you're good to go. You can adjust that retard out of the chain with a woodruff key if you're so inclined, and set IP timing when you swap out injectors... though there are different ways of going about getting things all where you want them when you swap out injectors, that's just what I'd probably do in your case. But, then again, you seem to be pretty knowledgeable, unlike myself, so you might opt for one of the other paths... I try to make things as easy as possible for myself (in some ways when it comes to these cars) as I am just learning about engines.

For instance, I've read that you can adjust the IP timing at any point, since it's so easy to do... let's say you adjust it every time you adjust your valves. Then your chain and IP are in 'Harmony.' just swap out your injectors at that point, and you should be good to go... I have no idea, however, how that would fit into the mechanical argument for the longevity of our engines (i.e. less powerful popping injectors as chain stretches)... That's why I suggested doing a clean sweep of tings that need to be tended to when you do swap them out..

In any case, if you come across better info in your searches, I would be obliged if you let me know, as I'd like some clear answers to this as well for when I'm ready to tackle the same thing myself...

My chief concern here is not stuff like the cogs, tensioner and rails, which can be easily monitored and inspected, but the nature of the chain while it stretches to different lengths...
 
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