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Old 01-30-2008, 12:43 PM
fireman1073's Avatar
Join Date: Nov 2005
Location: new bedford Massachusetts
Posts: 179
shaking like a paint mixer

After trying all the usual suspects (rack dampner bolt, filters, injectors, etc) car still occasionally shook at idle.

I thought it was the veg oil.

Finally figured it out.

When fuel is hot it shakes.

I shut my heat exchanger off with the ball valve and perfect idle.

I have one for my veggy oil conversion.

Other than that no problems on veg oil in over 13,000 miles.

Why would 180 degree (checked with infrared gun) fuel cause shaking?

I tried running straight diesel in my veg oil tank to diagnose and discovered the heat was making the shake no other thing.

heat on=shake heat off=smooth, that simple!

oh! 1984 300sd two tank conversion coolant heated only.

does the heat cause expansion in the delivery valves, pump or injectors and cause sticking?

My other conversion 83 300d had no such problem, in fact it ran considerably smoother on oil.


85 300d in progress
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Old 01-30-2008, 01:24 PM
muleears's Avatar
Old MB Driver
Join Date: May 2006
Location: Windsor, VA
Posts: 1,435
If you haven't already you may want to try the Greasecar or Biodiesel Infopop forums, they have many more greasers.

To address your question: could you possibly have an air leak in a connection to your heat exchanger that is letting in air and causing the shake (poor idle)?

I wish I had that kind of heat in my car, I only get around 120*f before the IP. Good luck.

'07 E320 Bluetec 133K my DD
'04 Jaguar XJ8 VDP, 34K
'10 Hyundai Accent 60K Grocery Getter
'02 VW Golf soon to be on the road again
'97 E300 Diesel Son's DD
'61 VERY tolerant wife

Hampton Roads, VA USA

Gone but not forgotten:
'67 250S 95K
'86 300SDL
'87 300D Turbo, 364K! R.I.P.
'98 E300 Turbodiesel, 213K
'02 S420, 164K
'01 Prius 138K
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Old 01-30-2008, 11:09 PM
bgkast's Avatar
Rollin' on 16s
Join Date: Dec 2005
Location: Vancouver WA
Posts: 6,528
Check to see if it is missing on one cylinder.
1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine
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Old 02-07-2008, 09:33 AM
fireman1073's Avatar
Join Date: Nov 2005
Location: new bedford Massachusetts
Posts: 179
found the problem.

air leak at the exchanger.

I could not find it because apparently when cold it does not leak but after it heats up the cast elbow must expand differently than the stainless heat exchanger creating the leak only when hot.

weird huh?

tough one to find.

thanks for the suggestions


85 300d in progress
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