603 Shakes at HOT idle-Could it be out of balance injectors?
 

My 300d shakes a good bit at idle (only when HOT- it's smooth as a top when cold). Could this be that the injectors are out of balance? I installed Bosios myself and never had them pop tested. They're very quiet and smooth as can be. But when the engine is hot (especially so after a long drive), it'll shake my knee back and forth at idle.

I replaced the original (nailing) injectors right after buying the car. I never drove it far enough to know if it did this before.

I asked the dealer where I had it timed a year ago what he thought and he said weak IP or injector problem. He said have them pop tested.

Replace fuel filters and/or check tank strainer and vent.

That's all new except the vent. I've run it with the fuel cap off which should allow it to breathe easy. Still pretty shakey.

When run on any kind of oil it's smooth as a top hot or cold.

I'm pretty baffled on the shake. I almost want to mess with the IP timing a bit +- a degree or two each way but I'm not sure of a good method of making sure I can get back to the starting point if need be.

check the fuel strainers and filters
they always say this. I think its your IP. Based on my experience, the pump seals differently as they warm up, and it takes a while for the heat to build up in the IP due to circulating engine oil. The 603 is normally a very smooth engine and it has much less tendency to lope like the 617's. So to shake that much hot is indicative of a serious imbalance in pressure. First thing to check however are the nozzles
then let us know.

I think it is too. I don't plan on having the IP rebuilt unless it dies on me. I do notice that any thicker oil seems to smooth out the shake. I don't know what this would be.

Mine will do that as well once in a while after a long highway run on a very hot day. I was told by the local Bosch diesel shop that its probably the IP. Its not the injectors.


You can feel it in the car, its a back and forth motion, the engine is rocking. Like a 617 with a bad rack bolt.

It doesn't bother me enough to cough up $1k for an IP rebuild. Eventualy though, throw that in with the bottom seal leak, and a few other poor running symptoms of an old IP...

Sad, sad, sad. But these are old cars. They wear out like anything I guess. It'll be worth the $1k to keep them on the road. But like you, I'll hold out. I'm wishing it were something else than the IP but chances are it probably is.

By thicker Oil do you mean Oil you use as fuel or Oil going in the crankcase?
Also did it start shaking after the Bosio Nozzles were installed or did it run OK for weeks or months before the shaking started?
If burning thicker oil makes it run smoother it may well be the injectors or a IP timing issure (related to timing chain stretch ???). If the injector pop pressures are out of spec it could also effect the timing. Pop pressures lower than spec means early injection higher than spec means later injection.

Unless it gives out in the meantime the IP is number 4 on the list of big ticket repairs.
1. Transmission
2. Paint
3. Interior
4. IP

So its on the list.:D

I've been looking for solutions to a hot idle shake and found more than one member solved the problem with new engine shocks.

Ha, yeah I'm with you. My car's roof was as baked and cracked as can be. I paint guitars all day so I repainted it. At this point though, I'm going to let my 300d take it's own course. It's impossible to keep up with everything. More fun to just drive it and let it slowly die, I bet the IP's still got another 100k in it. I had a friend in High School who's dad was a manager of the diesel mechanic shop for the city. Very sharp guy. He drove a 73 220d and loved that car. He could have had that thing sparkling up one side and down the other. But he just drove it. I think it had close to 400 or 500k when the rear end finally gave way and he junked it. But he wouldn't repair anything on it. GP's went and he'd just wedge the ice scraper to the accelerator when trying to start it in the winter (10F outside). Fire it up, go eat breakfast and when he came back it'd be running smooth.

I'm not that bad but the more stuff that gives way and I'm having to fix, I'm getting close!;)

How are the motor mounts?

They are original as far as I know. Probably could use a change. They seem different than w123 rubber mounts. Do ours wear out regularly on the 603's hydraulic mounts?

Before you rebuild an IP or go replacing shocks and mounts and everything else my suggestion is to do a compression test when it is in the faulty state.

The test costs little ($30 for a tester at HF) and it will qualify the most basic requirement of the engine. What if you find that there is an interchange happening between two neighboring cylinders? All of the work and expense on the other items would have been a waste.

yes, 603 mounts are not long lived things! they are more like gel filled donuts than the solid rubber mounts used in the 123.
If you shake the engine you can judge whether the mounts are getting weak, on the 603 the fan can hit the shroud when the mouonts go out. Ask greasybenz.

However, even a weak mount will not result in an engine loping side to side unless there is a basic underlying reason for it to run ragged at idle.
The best plan would be to check the injectors first (thats easy), a compression test at the same time the injectors out, then take it from there.
+ replace the heat shileds under the injectors when you replace them.
Like I said the 6 cyls just normally idle so smoothly they're amazing.