I've done a lot of reading regarding a vacuum leak causing a transmission to down shift hard. I believe I have a vacuum leak because my door locks don't always work and there's no heat from the center vents.

Can I just plug the vacuum at it's source if I don't care about the locks ever working or the center vent? If so, where and how do I do this? I'm not familiar with this type of system/procedure. I've had the car for two years and keep learning of all its quirks.

Thanks!!!
Brian

In the engine bay near the oil filter. The yellow lines are for the locks, and the green one is for climate control.

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

You never get heat from the center vents, only cold air. Normal for this car.

Get a MitiVac hand pump and use it to find the leak. I'd bet all the rubber connectors (most of which can be replaced with plain vac line) are bad, that's why you have a vac problem.

Also check the orfices on the main line where the other lines connect -- they have a tendency to get plugged.

If you block the climate control lines you will only have defrost -- vac is required to operate the floor vents.

What year is your 300D?

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

It's a 1985 300D Turbo. Sorry, I should have specified that. I really don't care about getting the vents to work again. The defroster is all I care about. Same goes for the locks. I never lock her up since it's too damn cold here half the year and they freeze up anyway.

You can plug the lines to the locks and the climate control, but that will only fix the tranny problem if the leak is so bad the vac pump can't keep up -- the EGR and tranny control line comes from a different nipple on the vac line.

The transmission control lines are white -- should go from the main vac line between the pump and the brake booster to a box on the IP (may be on the valve cover, I don't remember), then to the EGR and to the blue vacuum amplifier on the driver's side fender. There will be a line straight from the main line to the vac amplifier, too, I believe.

Check all the rubber bits on the hard plastic lines for condition. They must be flexible but not sticky. If they are rock hard, cracked, or mushy, replace them. Get a MitiVac and hook it up to the mail line in place of one of the hoses and verify that you have sufficient vac from the pump -- 17" min, I believe, after a few minutes running.

If the pump never develops much vac, it's either shot or the check vavles are bad, you will have to fix it (eventually the power brakes won't work, either.). If you have good vac, check the vacuum going to the transmission modulator from the vacuum amplifier -- should be at least 15" at closed throttle, dropping to 12 or so as soon as you crack the throttle, then gradually dropping to zero as throttle goes wide open. Easier to check if you have a suction vac source rather than running the engine ---/

Make sure the vacuum line to the transmission modulator is good -- should hold vac indefinitely.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

No offence, but man, it's fairly cheap and easy to fix correctly. Unless it's an absolute junk car, your doing it and it's next owner a dis-service.

technicaly I am judging, but I really intend no offence..

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

the car just needs to get me through the rest of graduate school until i finish my doctorate (<1year) and then she's going to the junk yard. the past two winters in northern, ny (really northern!!!) have put a huge toll on her. she's pushing 300,000 miles and i don't want to sink any more money into it. if you'd like to come up here and fix it for me for free then i'd be glad to accept.

If you were any closer I would.

I can accept the rotted out northern car answer though. Shame though...

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

alright... so you guilted me into at least looking at the lines and seeing what i could do.... BUT upon trying to open the hood i snapped the hood release lever mechanism. when does it ever end?!?!?!? oh well, at least it's only -15F outside.

It's a two decade old car, it will end two decades from now when you've replaced everything on it. THEN, it will start over again the year after that.

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

odonnebj....the hood release lever on the grill? If so, this part is only a few dollars. You can get the hood open by using a coat hanger and pushing it through the grill and catching the hook that the hood release is attached to. There is probably still a piece attached. You can plug those lines if you don't care about them. Maybe wait until spring to look into getting them working. I'm not sure if this will fix your shifting though.

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RT


1984 300D---Sold
1995 E420 - 106K - Brilliant Silver Metallic/Orion Gray --- Sold
1984 300SD - 151K Manganese Brown Metallic/Mostly Black --- Sold
1982 240D - 79K - Manila Beige/Palomino---Sold

If it is the, inside the car, hood release you can use a pair of pliars or channel locks or whatever to pull on the cable...goodluck and just be patient..maybe waiting on spring is a good idea...

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James A. Harris