High Idle, White Smoke, shifting funny, HELP!! 75 240D - PeachParts Mercedes-Benz Forum

Ronkat81 · #1 10-01-2011, 11:16 AM

Hey Team,

I need all of your collective wisdom, I have looked over many posts about the high Idle trouble that often plagues the 240d's. A week ago I purchased a Dove Gray 1975 240D Mercedes. She is Clean. . . 3 dings that can be pulled out. in order to make her show room the carpet will have to be replaced although it isn't bad. One crack in the dashboard, other than that she is gorgeous!! I paid 1,850 for her.

Pretty good? Anyway on to the tech questions. To get her home I drove her 140 miles. No problems at all. Now i did notice when I was driving home on the highway that everytime i took my foot off the gas that there would be a nice cloud of white smoke billowing out of the tailpipe.

Also when I would stop the engine is idled up high. Now when you put it in gear it goes down and idles slowly. when you first crank it it idles as it should but as it warms up (3-4 minutes) it is raging. I know I probably need to adjust the valves I'm sure, but who knows? anyway i adjusted the idle on the air intake all the way closed. . still Idling high. I adjusted the idle control (the knob adjuster) all the way until it wasn't touching anymore. I also disconnected the linkage so that I could operate the air intake as I wished and still had no success. The only way to slow it down was to push in on the emergency stop and this would slow it. Then I unhooked the vaccume line from the intake and plugged it to see if it was getting too much air from a vaccume leak somewhere... Still a high Idle. Ok so that is problem one. Next is the shifting... I'm wondering if it is all related as when the all Mercedes do it starts in 2nd gear quickly shifts through 3 and into 4th. By the time i am running 15-20 mph I am already in 4th gear regardless of whether I am to the floor or not. I have noticed that she is losing a little bit of water (hopefully not a head gasket) but the only time she puffs the white smoke is at the high idle or when I release the gas when traveling at a good speed. Any Ideas??!?!

Stretch · #2 10-01-2011, 01:53 PM

Sorry if you are losing water and getting white smoke then it could be the head gasket.

Are you getting oil in the water?

Is there a white emulsion in the coolant?

I think you should do a leak down test to check

Leak-down tester - Wikipedia, the free encyclopedia

As for the shifting - probably vacuum related

PeachPartsWiki: Transmission Vacuum Modulator Adjustment

DIY W123 Transmission Diagnose and Adjustment 722.xx OM 616-7 - Benzworld.org - Mercedes-Benz Discussion Forum

Have a look at your linkages

http://www.peachparts.com/shopforum/diesel-discussion/184774-wow-adjust-your-throttle-linkages.html

EDIT (number 2)

Make sure you've not got a head gasket problem before fiddling with anything else. You'll save yourself a lot of bother!

kerry · #3 10-01-2011, 05:01 PM

Not a head gasket. Your vacuum pump diaphragm has failed and it is pumping oil into the intake via the plastic hose that runs from the vacuum pump to either the air cleaner or intake manifold. This accounts for both the high idle and the poor shifting. Pump is no longer producing adequate vacuum causing the poor shifting and oil going into the manifold is increasing your idle speed. Not a difficult repair.

Ronkat81 · #4 10-01-2011, 10:18 PM

Thanks guys. . .I'll Def check everything out. . . @ Army, i'm afraid that it is the head gasket. . I hope not.. there isn't any mixxing of the oil and water yet. . . so there is still hope I guess. . . i saw one place on a hose where it is possible that there could be some leakage. Are head gasket repairs difficult for the home user on this vehicle? @ Kerry, I was wondering about that as well, I did disconnect the vaccume line and plug the inlet in the manifold but it still was running fast :-( hopefully I didn't purchase a dud. . .

Ronkat81 · #5 10-01-2011, 10:21 PM

Ah i also meant to add that when I run the vehicle with the oil fill off it does pump alot of air out of the hole, however this neither changes the speed of the engine nor does there come any smoke out, just flinging of oil. . .

piccolovic · #6 10-01-2011, 10:49 PM

Quote:

Originally Posted by Ronkat81

Ah i also meant to add that when I run the vehicle with the oil fill off it does pump alot of air out of the hole, however this neither changes the speed of the engine nor does there come any smoke out, just flinging of oil. . .

Sign of Blow-by???

Stretch · #7 10-02-2011, 02:02 AM

After reading the subsequent posts I think you'd be wise to follow up kerry's advice first.

Don't fiddle with anything else!

Stretch · #8 10-02-2011, 05:28 AM

After further consideration!

My opinion is as follows (!)

Kerry is often right so it is worth while doing what he says first.

However I don't think that the vacuum pump is necessarily an easy job. When sitting in an arm chair reading the book it looks straight forward and indeed I'm sure it can be. But in the real world you might find that the screws on the cover of the vacuum are corroded and nearly impossible to remove without damaging something.

If the pump gets damaged the replacement cost is high. I think a brand new part will cost the best part of 1000USD... so there's half of the OP's purchase price. Second hand parts are cheaper but 'cos everyone knows how much the new ones are... well they're not cheap either...

...so be careful with the vacuum pump...

Ronkat81 - if you have compressed air and a leak down tester to hand then there is nothing wrong in making a measurement. However perhaps the quickest check to do before you even consider vacuum pumps and vacuum testing is to push up and down on the brake pedal with the engine off and listen out for any air chuffing out of the front of the vacuum pump...

EDIT - I forgot the most important point!

WARNING - there are lots and lots of threads on this forum where people have been chasing their tails trying to get this sort of problem fixed.

When I say don't fiddle with anything else - I mean try not to fix everything all at once. Do one thing - do it well. Best of luck to you!

kerry · #9 10-02-2011, 10:08 AM

Hmmm, I thought I posted something last night but it isn't here. When you say you removed the vacuum line from the intake manifold, you are referring to the vent line from the vacuum pump and not the PCV hose right? The vacuum line from the pump shouldn't have vacuum in it, it should have pressure since it is venting the pump. If you did remove the vacuum vent line and it did not have oil in it, then that is not the cause of the problem.
Not sure how the 115 shift control mechanism works. On later models the quick shifts could be explained by a maladjusted bowden cable but yours may not have one.
Can you say more about the idle on the air intake. That topic does not come up on here very often but I assume it has something to do with the butterfly valve in the intake manifold? What kind of adjustment is there?

Ronkat81 · #10 10-02-2011, 10:36 AM

I deff appreciate all of your help! You guys are awesome.. I'm going to see if I can post pictures up here. @army I will def check that brake test! Thanks for that tip and see if I can do a leak down... :-( I might have to buy some parts for that lol. @kerry when I disconnected the vaccume line it was from the output side where it feeds into the intake manifold via the bolt contraption. Then I plugged the hole in. the intake with my fiber (bad idea I know lol) and this didn't change the racing of the engine, but there wasn't any oil coming from the output line of the pump. Another thing I forgot bc I was reading that the governor could cause this was to remove the little small line that runs from the injection pump around to the butterfly air intake and played with applying various pressures to each side.. No results.. Idle never changed...

kerry · #11 10-02-2011, 10:44 AM

Forget the vacuum pump then. No oil in that line means it's probably ok. There's not a lot of knowledge on here about the early 616's with the butterfly valve and how it is adjusted.

Ronkat81 · #12 10-02-2011, 10:59 AM

I'm wondering if I should sell it and try to get my money back out of it? If it is the head gasket could that make the engine race? Or maybe just a good valve adjustment will stop the white smoke? The water loss is really slow..not alot and if I run the car without the radiator cap on there isn't any diesel smell or exhaust in there....

kerry · #13 10-02-2011, 12:35 PM

I certainly wouldn't assume you have a head gasket problem without some kind of confirmation. A bad headgasket would not make it race. I don't think a valve adjustment will make much difference with the smoke. Why do you think it will? You need to figure out why it is smoking. Make a video of the smoke at idle, with the engine at higher rpm while still and at various road speeds, possibly utilizing a videographer in a car behind you. Post it on YouTube or somewhere like that and link it here. Without some visual evidence it's really hard to know what is happening and how seriously to take the smoke.

Stretch · #14 10-02-2011, 12:44 PM

I'm just starting to get into how IPs work. (http://www.peachparts.com/shopforum/diesel-discussion/306090-papas-got-brand-new-om617-ip-play.html) Reading the FSM last night, the MW pumps - the early ones - do rely on a vacuum differential between the atmospheric pressure (there's a little mushroom air filter on the top of the IP) and the pressure created by the vacuum pump. It is all to read in chapter 07-010 in the non turbo FSM.

Ronkat81 have you got a FSM? (Factory service manual - the one from Mercedes)

leathermang · #15 10-02-2011, 01:50 PM

Of course it is always possible on cars this old to have more than one problem at a time..

Does the car smoke more upon Cold startup than it does running warm?

Notice in the upper right part of the old guys posts.... their location is shown... that sometimes proves to be very valuable... I assume the law or ex's are not trying to track you down....