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Brian77 12-24-2009 03:30 PM

300SD Will Not Shut Off
 
1 Attachment(s)
Happy Holidays,

It seems that my car ('85 300SD) hates the cold. The car has recently been cursed by the god Leaky Maximus, in which I have recently fixed a leaking oil pan gasket and leaking power steering pump since the cold weather. Now the car has developed a vacuum leak that prevents it from shutting off other than using the Stop lever in the engine bay. Also, the transmission has developed a rather harsh shifting at the same time. I have spent some time looking at vacuum diagrams and testing various lines with a vacuum pump and think that I have isolated the problem to the main line from the vacuum pump to the brake booster. However, while I ordered the part from the dealer, to be on the safe side, would appreciate a second opinion about whether this could be the problem. I have attached a picture of the vacuum line with comments from when I tested it with the engine running. The car will shut off if I use the hand held vacuum pump.

I tried to rig a temporary solution of running all of the lines through the one outlet on the vacuum line in the picture that seems to have vacuum present, but this fix did nothing to solve the problem of the car not shutting down with the key. BTW, I tried to avoid this problem by having the vacuum shut off valve replaced over the summer.

Thanks,

toomany MBZ 12-24-2009 03:49 PM

It would seem the piece with the split offs has failed, let us know how the new line works out.

Brian77 12-24-2009 04:00 PM

Thanks, too many MBZ. Of course, my normal parts source does not have this item, and the dealer does not stock it. I have to wait until Wednesday to get it from the dealer. Unfortunately, it seems that the dealerships around here do not stock many parts for these cars anymore beyond filters, glow plugs and other minor maintenance items.

Burnzy 12-24-2009 04:03 PM

I had a very similar experience with my car Brian. After weeks of testing and pulling hair out I took a straightened out paper clip and GENTLY inserted it into each of the two nipples that come off the brake booster line. Like magic, my tranny shifted smooth and my car shut off instantly. It's worth a shot. I have learned that sometimes the manufacturing process is less than stellar on the booster lines and some of the plastic from the nipples is not removed completely on occasion and ends up causing vacuum restriction. Good luck!

kerry 12-24-2009 04:04 PM

Shut off problems that emerge in cold weather are often caused by leaky vacuum pods in the climate control system which are not activated in warmer weather. Try pushing the far right button on the climate control system and see if the problem of not shutting off/hard shifting goes away.

toomany MBZ 12-24-2009 08:02 PM

Quote:

Originally Posted by Brian77 (Post 2367499)
Thanks, too many MBZ. Of course, my normal parts source does not have this item, and the dealer does not stock it. I have to wait until Wednesday to get it from the dealer. Unfortunately, it seems that the dealerships around here do not stock many parts for these cars anymore beyond filters, glow plugs and other minor maintenance items.

Yeah, these cars are old enough for the dealer not to stock a bunch of parts for 'em.

rooster6224 12-25-2009 10:33 PM

you can try unplugging at the vacuum harness at the firewall the two yellow lines. Use a golf tee to plug the rubber y-harness. you may not get heat out of the center vents anymore but if the source of the leak is in the dash this will confirm where the problem is but most importantly you will avoid those embarassing moments at the grocery store having to open the hood to shut it off.

jkubica 12-25-2009 11:52 PM

Quote:

Originally Posted by Brian77 (Post 2367487)
Happy Holidays,

It seems that my car ('85 300SD) hates the cold. The car has recently been cursed by the god Leaky Maximus, in which I have recently fixed a leaking oil pan gasket and leaking power steering pump since the cold weather. Now the car has developed a vacuum leak that prevents it from shutting off other than using the Stop lever in the engine bay. Also, the transmission has developed a rather harsh shifting at the same time. I have spent some time looking at vacuum diagrams and testing various lines with a vacuum pump and think that I have isolated the problem to the main line from the vacuum pump to the brake booster. However, while I ordered the part from the dealer, to be on the safe side, would appreciate a second opinion about whether this could be the problem. I have attached a picture of the vacuum line with comments from when I tested it with the engine running. The car will shut off if I use the hand held vacuum pump.

I tried to rig a temporary solution of running all of the lines through the one outlet on the vacuum line in the picture that seems to have vacuum present, but this fix did nothing to solve the problem of the car not shutting down with the key. BTW, I tried to avoid this problem by having the vacuum shut off valve replaced over the summer.

Thanks,


Hi
You might want to go over to www.dieselgiant.com and look at the DIY pictorial on vacuum system troubleshooting

The first step is to read the vacuum at the brake booster end of the big main vacuum line with both nipples plugged with a short piece of tubing and golf tees or the like - you should get full vacuum. If you do it means that that line, the check valve and the pump are all working. Then go from there.
Good Luck,
Joseph

okyoureabeast 12-26-2009 01:34 AM

Quote:

Originally Posted by rooster6224 (Post 2368236)
you will avoid those embarassing moments at the grocery store having to open the hood to shut it off.

I don't know about you, but I enjoy those scared looks as I press some mysterious thing under my hood for my car to putter off!

Burnzy 12-26-2009 08:01 AM

Brian. Is your EGR still hooked up? That was the biggest leak I ran across in my vacuum war.

Brian77 12-28-2009 07:11 PM

Thanks, everyone for your suggestions and will keep them in mind. I hope that it is not a complicated mess to fix. It was pouring rain here the other day and having to open the hood and have the water collected in the grill drip on my head is not fun.

Yes, the EGR valve is still connected in the car. I tried the paper clip suggestion to see if there was some sort of blockage. Unfortuantely, a good idea that didn't work.

I find it strange, though, that the same line pulls vacuum from the large white nipple but no vacuum from the 2 smaller ones on the same line. I have also disconnected the one brown line from one of the smaller nipples not pulling any vacuum. Upon connecting the vacuum pump, the car immediately shuts down.

Brian77 01-04-2010 10:59 AM

300SD Won't Shut Off Update
 
Well, as an update, again thanks everyone for the suggestions.

Unfortunately, my vacuum leak was a complicated mess to fix.

I was convinced that the brake booster line was at fault. After ordering a new line and installing it in the dealership's parking lot with the cold wind howling, of course, it didn't work.

So, I again got my trusty vacuum pump and discovered that the leak was coming from the climate control. Fortunately, over the summer, knowing that these cars suffer from ruptured vacuum pods in the dashboard, I had ordered all of them but never had the time to install them.

I tackled the job this weekend in the garage by removing the entire dashboard and center console to replace all 6 of them. This is the first time that I have tacked this enormous job. In my opinion the climate control system is the most overengineered piece of garbage that Mercedes engineers ever devised, only matched by their clear arrogance by the placement of these garbage components that none of them would ever need to be changed.

The job was a mixed success. The car now shuts off immediately, and I now have heat coming from the floor (did not use to have heat from this source); however, it appears now that I have to troubleshoot why, with the rush of the blower motor, the rush of warm air is flowing from the defrost vent and faintly from the floor with nothing from the side vents. So, it appears that I will now have to go back into the dashboard and diagnose this gremlin. As I understand, it could be anything from jammed flaps to a monovalve to a cracked CCU unit.

Graplr 01-04-2010 11:05 AM

Quote:

Originally Posted by Brian77 (Post 2374021)
As I understand, it could be anything from jammed flaps to a monovalve to a cracked CCU unit.

You can eliminate the monovalve as a source of the problem. The monovalve does nothing to control air flow. If your temperature was erratic or changed will driving, then it may be a possibility. I also think too many jump on the resolder the CCU bandwagon. I would look elsewhere first.


I would start by checking the air flow path. Did you hook all the air lines back up properly when reinstalling the dash? Then I would look at the flaps/controls.

toomany MBZ 01-04-2010 11:07 AM

Quote:

Originally Posted by Brian77 (Post 2374021)
In my opinion the climate control system is the most overengineered piece of garbage that Mercedes engineers ever devised, only matched by their clear arrogance by the placement of these garbage components that none of them would ever need to be changed. Here, here!

The job was a mixed success. The car now shuts off immediately, and I now have heat coming from the floor (did not use to have heat from this source); however, it appears now that I have to troubleshoot why, with the rush of the blower motor, the rush of warm air is flowing from the defrost vent and faintly from the floor with nothing from the side vents. So, it appears that I will now have to go back into the dashboard and diagnose this gremlin. As I understand, it could be anything from jammed flaps to a monovalve to a cracked CCU unit.

The 126's have a weak link on the drivers side floor vent flap. Mine was broken and the fan pushed it closed. I rigged the flap (door) open, doing so without having to go too far, just remove the lower kick panel.
I also have other issues that I'm afraid I'll have to dig into it as far as you did.
Did you take any pics of your repar?

Brian77 01-04-2010 11:09 AM

Thanks. Hopefully, I did reinstall the lines properly. I was careful to only do one vacuum line at a time when replacing the pods to ensure that I did not mix up anything.

The temperature is constant no matter the speed or engine idle. The problem is the air flow.


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