Hi all,

I've done some searching and found a lot of great write-ups. I guess I am not sure where to start, so I'm posting for guidance.

1992 300D 2.5 turbo, 289k.

Most recent issue car has developed is the door locks lock all by themselves after about 5-10 minutes of driving or if the car is sitting shut off. I can unlock them with they key and a they all will unlock, but will be temperamental and lock again right away or lock in a minute. I can unlock and lock from the trunk key.

The climate control temperature has always been either full hot or full vent. Fan speed seems to be stuck on low, or sometimes the fan does not come on at all no matter what the dash setting.

When colder outside temperatures, the brake pedal will be rock hard for about 30 second after starting, then goes back to normal after that.

That all being said, transmission shifting is basically fine and acceleration is good.

From my searching, the car probably has a number of issues. The door locks and climate control are the priority as it's winter here now.

Any suggestions on where a failure is most likely that I can look at first?

Thanks....

-m

__________________
Now:
2018 Tesla Model X
1999 S500 Grand Edition 164k
1992 300D 2.5 Turbo 287k
2005 E320 4MATIC wagon
1991 Alfa Romeo 164L 99k (sleeping for a while)

Then: 96 Lincoln TC, 93 Lincoln TC, 87 560 SEL, 87 300 SDL, 80 300D, 89 560 SEC

Door Locking (Unlocking) [+ Fuel Flap Door and Trunk] are controlled by an air
pump under the passenger side rear seat.Electric Micro-Switches in the
Driver/Passenger/Trunk locks control the actuation of the ("Negative Wind")
SUCK to Lock/BLOW to Unlock Pump.This is further complicated by the
"Comfort Control"System (A Relay in the fuse box and The "BOX" under the
driver's side rear seat.)

Some Modern automobiles "AutoLock" over a set speed BUT your anomaly
sounds like it could be a short?

The CCU issue (Climate Control Unit) MAY be a compromised Monovalve
combined with an actual Control Unit inability to regulate the Blower.

Arthur Dalton has a number of answers in his reply to posts on CC issues:

PeachParts Mercedes ShopForum - Search Results

__________________
'84 300SD sold
124.128

compress ignite,

Thanks for that info. Another thread you posted in also is being helpful:

http://www.peachparts.com/shopforum/diesel-discussion/228092-door-locks-w124.html

I'm attacking just the door locks first as it appears to be an isolated system from the engine-generated vacuum.

Will post any findings.

Do you know of a post that describes how to remove the door lock bits from the front door for my year, by chance? I figure I will be headed in that direction at some point.

Thanks.

-m

__________________
Now:
2018 Tesla Model X
1999 S500 Grand Edition 164k
1992 300D 2.5 Turbo 287k
2005 E320 4MATIC wagon
1991 Alfa Romeo 164L 99k (sleeping for a while)

Then: 96 Lincoln TC, 93 Lincoln TC, 87 560 SEL, 87 300 SDL, 80 300D, 89 560 SEC

Is there an aftermarket security system in your car?

I'd make the brakes the first priority. There's either a massive vacuum leak, a faulty check valve or tired vacuum pump causing the brake pedal symptoms. The pedal should feel as it should within a second of starting the engine if not just from cranking. If it's an old style pump, that might be reason enough to replace it.

Sixto
87 300D

Is there an aftermarket security system in your car?

I'd make the brakes the first priority. There's either a massive vacuum leak, a faulty check valve or tired vacuum pump causing the brake pedal symptoms. The pedal should feel as it should within a second of starting the engine if not just from cranking. If it's an old style pump, that might be reason enough to replace it.

Sixto
87 300D

Hi, the car does not have a factory or after market alarm system.

I have observed the vacuum pump under the back sear. It runs for exactly 30 seconds when activated by using the key in the door lock or moving either front door lock pin up or down. Does that sound like the correct amount of time for it to run? The lock pins move promptly after locking/unlocking the car.

If you have unlocked the car, after a few minutes to pump comes back on and the doors lock all by themselves.

Is there a way to disconnect the electrical connection going to a door to see if that door is giving the signal to lock to the pump? without slicing up a ton of wires if possible. I see 6 wires coming off the round plug on the vacuum pump, but there is like no slack in those wires... I presume they go to the front door and trunk locks.


Regarding the brakes, I have a mityvac but never really figured out how to use it. Most posts say to hook it up and test, but I'm a bit clueless with this vacuum stuff (I'm an IT guy). Can you (or someone) give me a little more detailed instructions on how to troubleshoot the main engine vacuum items? or a link.. I have model 04050 Silverton Plus Automotive Kit.

Thanks.

-m

__________________
Now:
2018 Tesla Model X
1999 S500 Grand Edition 164k
1992 300D 2.5 Turbo 287k
2005 E320 4MATIC wagon
1991 Alfa Romeo 164L 99k (sleeping for a while)

Then: 96 Lincoln TC, 93 Lincoln TC, 87 560 SEL, 87 300 SDL, 80 300D, 89 560 SEC

Found some troubleshooting info from dieselgiant for W123... I imagine is similar for me and will try some.

Mercedes Vacuum Troubleshooting

__________________
Now:
2018 Tesla Model X
1999 S500 Grand Edition 164k
1992 300D 2.5 Turbo 287k
2005 E320 4MATIC wagon
1991 Alfa Romeo 164L 99k (sleeping for a while)

Then: 96 Lincoln TC, 93 Lincoln TC, 87 560 SEL, 87 300 SDL, 80 300D, 89 560 SEC

Ok, I did the first vacuum test from that page by removing the connection to the brake booster. I connected my mityvac with a plastic cone-type connector so the seal would be good. With the car running, I am seeing 20 hg vacuum. When I turn the car off, the reading drops to 15 hg. When I start the car again, the reading stays at 15 hg for about 10 seconds and then immediately raises to 20 hg and then stays there.

The dieselgiant page says I should be seeing 22 hg with the car running. So I am slightly low from that. Also, the observation that the vacuum does not raise to operating levels immediately after starring the car is probably the brake pedal issue...... some days maybe the pump is cold or something and takes 30-60 seconds to get up to proper levels.

So what does this mean? My take is pump is not making enough vacuum and/or starting to fail....

Let me know what you think. Thanks.

-m

Ps: I appear to have the original vacuum pump (no exposed screws on the cover) http://www.peachparts.com/shopforum/diesel-discussion/235329-300dturbo-tranny-hard-shifts.html

__________________
Now:
2018 Tesla Model X
1999 S500 Grand Edition 164k
1992 300D 2.5 Turbo 287k
2005 E320 4MATIC wagon
1991 Alfa Romeo 164L 99k (sleeping for a while)

Then: 96 Lincoln TC, 93 Lincoln TC, 87 560 SEL, 87 300 SDL, 80 300D, 89 560 SEC

30 seconds sounds like the full pump cycle which suggests a leak in the central locking system. The pump runs for a couple of three seconds with a tight system. A leak won't cause the system to lock as you describe, though. If you don't have your own copy of the FSM, check www.startekinfo.com for an online version. It'll have a wiring diagram of the central locking system so you can identify door triggers. What you describe really sounds like there are remnants of an aftermarket security system in your car. I've seen Euro 123s and 124s with doors that lock when the car gets to speed but they don't wait 5-10 minutes.

One test of the brake vacuum system is to disconnect and cap the auxiliary port at the engine vacuum pump, the small nipple, and the shutoff supply port by the brake booster line check valve. Go easy with the check valve fitting because it'll be very brittle. If the brake pedal feels 'normal' immediately when you start the engine, there's a massive leak in one of the branches you disconnected. If there isn't much improvement, keep looking, but you're down to a tired pump or leaky booster. I'm not aware of a test procedure for either. Maybe you can pressure test the booster.

Does the ACC fan blow on low even in DEFrost mode or with the fan control set to MAX? It's a PITA to get to the blower motor under the wiper assembly but I'd start by trying a good used blower. Mind which way the cage vanes face. Use some evaporator coil cleaning foam while the blower is out.

Sixto
87 300D

Thanks. The door lock thing is a more recent issue... maybe started August or September this year. I'll check out the started for troubleshooting info. Some door actuator has probably failed, I'm guessing. Our 2005 wagon has the auto door looking after you get underway, but this car does not have that feature.

The brake pedal thing has been pretty infrequent. Happened once in the morning earlier this week but not since then. Is there any other way I can test even if it's not doing it? Or can I hook up a semi-permanent vacuum gauge to the brake booster line so I can monitor it when the brake has the problem? Like add a T to the line and run it into the cabin somehow?

The climate control fan blows low even in defrost, yes. The air does get redirected to the windscreen Actually, I noticed this week, the fan on HIGH does blow faster then the fan on LOW, but the amount of air coming out on HIGH is not as fast as it should be. A number of years ago the blower motor did fail and I replaced it, was not the most fun to change but I made it.

Thanks.

-m

__________________
Now:
2018 Tesla Model X
1999 S500 Grand Edition 164k
1992 300D 2.5 Turbo 287k
2005 E320 4MATIC wagon
1991 Alfa Romeo 164L 99k (sleeping for a while)

Then: 96 Lincoln TC, 93 Lincoln TC, 87 560 SEL, 87 300 SDL, 80 300D, 89 560 SEC