'83 240D, auto trans, 216K, all original, everything functioning normally up to this point.

Drove to work, as usual (about 30 miles), pulled in and parked, engine wouldn't shut off/batt light illuminated. After a slight delay (didn't think to time it) engine finally did stop. Thought, "hmmm, that was odd". Nothing like that has ever happened in the past. Got out and went to lock the doors...no go. Locks didn't actuate (no vacuum, apparently).

Went about my normal day, left the car at work til this afternoon (I have a work vehicle). Got in, engine fired right up (as usual), drove home. When I got there, after an uneventful drive, I parked and everything worked normally as far as the shutdown/lock up procedure went. No problem with the power assist on the brakes or shift points with the auto. Everything seemed ok.

Any thoughts? Where to start? Obviously, something leaking in the lock system. Haven't done any "looking/research", yet. Are the locks and engine shutdown on the same leg/source for vacuum supply?

As an aside, also on the way to work that same day, the blower for the heater/ac wouldn't turn on. None of the fan speeds worked. Don't see how that could've been related (but, I've been wrong so many times in the past).
On the way home, today, the blower worked fine on all three speeds.

Figures. Today was my last day at work til the new year. I was all set to change my trans fluid, drain the torque converter, new filter. Also, a couple other minor maintenance tasks over the next few days. Looks like another project has been added to list for me.
Never fails.....

Maybe you just imagined it?

How would you fix it without symptoms?

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

Good point. Don't think I imagined the engine not shutting off and the battery light illuminating. Ditto the doors not locking.
Just wondered if anyone has had intermittent problems, with these 2 symptoms, similar to this ?
Guess I'll just hafta wait til it happens again...
Dunno what to think about the blower motor. Although, I have heard of sporadic blower motor operation when they're "on the way out".
Thanks for the support....

They're not related. The blower is probably the brushes wearing out, you'll need to see if there is power to it the next time it doesn't work or strike the motor. If power and striking it works it is the brushes. Also check/clean/replace the blower fuse.

For the delayed shut down I'd start by checking to see if the shutoff diaphragm holds vacuum and inspect the rubber connectors in the vacuum lines.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

I've 100% had the same problem with the engine not shutting down occasionally. It's definitely a vacuum leak. Finding it is the hard part. I've had it with a leaky actuator (for the gas door lock) and because of cracks in the connectors under the hood. Look at the cheap/easy stuff first.

Cheap/easy stuff first, for sure!

Thanks for the "gas door lock" direction, too. I had taken mine out quite a while ago (after it started leaking) and put golf tees in the lines. Forgot all about it til you just mentioned it. Now that it's much colder, I'll bet they're not as tight/secure.
Will also look at the shutoff diaphragm and test it with the mity vac.

Was relatively sure the blower wasn't related, but what a strange coincidence. All occurring at the same time.

Funny because the very night before I was reading a link about removing the heater core/evap box....yikes! Looks like the blower motor is about the easiest part to replace in that entire set up....

Thanks guys!

Intermittent vacuum problems are often related to a failed check valve at the vacuum pump inlet. The valve comes apart and the components rattle around in the vacuum pump inlet, sometimes blocking flow and sometimes not.

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I am siding with tangofox in post 7.

You need to start of knowing what you your actual vacuum from the vacuum pump is. If you don't have a handheld vacuum tester you can barrow a vacuum gauge from most Autopart chain stores.

When the vacuum check valve has issues you still have vacuum but it is lower than the normal 22 mmof hg (I think that is what it is).

You can also remove the vacuum hose at the Vaccuum pump and the check valve and take a look and see if the parts are still inside of it.
The middle picture shows a vacuum check valve on the vacuum pump that fell apart. Normally the parts fall inside and cannot be retrieved. Having the parts fall inside does not damage the vacuum pump.

When I had your issue, I found that the check valve was full of gunk and hosing it out with WD-40 fixed the issue. Don't use brake cleaner as the valve is plastic.

Inspect the under the hood vacuum connectors.

In the last picture number 3 is the 2 in one check valve that goes to the door locks. Some models have 2 separate check valves instead of the 2 in one check valve.
Anyway, disconnect the valve from the vacuum source end and plug off the vacuum source end hose connector. If it shuts off reliably after that you have a vacuum leaked somewhere in the door locking system.

Attached Thumbnails

     

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84 300D, 82 Volvo 244Gl Diesel

Thanks "tango" and "diesel". Sounds like a great place to start and sound advice. Last time I looked at the check valve, probably a couple years ago, it was clean and in tact. I'll check the the vacuum pump with my hand held.

Thanks, "diesel" for the pics and trouble shooting procedure. Exactly what I was looking for. Hard to find an "intermittent" problem, especially if it's not acting up, but ya gotta start somehwhere.

I've recently done a cursory check of the under hood vacuum connectors and they all looked pretty good. Everything soft and pliable, no splits or tears. I'll take another closer look.

Thanks, again. Appreciate the direction.
I'll post what I find...

I will third the previous posts.
Also likely you use the brakes more before parking at work hen parking at home.
A weak pump won’t recover from each push of the brake pedal as quickly.

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My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Yep, I had some intermittent issues with the check valve on the pump.

Also I would consider any vacuum element (the 240d has only two climate control pods) that may have been toggled into position where they leak. Sometimes a pod will not leak when pulled one way but when pulled the other way it’ll open up a crack in the diaphragm.

Like some leaky lock actuators will leak when the doors are unlocked but seal up when the doors are locked. This can get really confusing when you mityvac your system and see no leaks but sometimes all your vacuum just gets lost for no obvious reason randomly or at least seemingly randomly.

You may have switched the CCU back to another setting which threw your flap into the direction where it no longer leaked. You drove home, pumped down your system and all was good again…till the pod gets flipped the other way and the vacuum leaks out.

The vacuum pods are much simpler on a 240D. My 300D turbo sometimes gets in a mode while flipping the floor flaps where it’ll be hard to shut down. Once I flip back to EC it holds vacuum. Just something to keep in mind.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

Sorry for being MIA on this thread lately. The holidays rolled in quickly and then came the "bomb cyclone" with winter weather we haven't seen in decades up here in the northeast.
Thanks for the recent hints/tips. Strangely enough (or, maybe, as usual) I haven't had one bit of trouble with the vacuum system since my OP. The check valve looks fine. All under hood vacuum lines look good, too.
I pulled the black plastic cover off of the 3/2 way valves (there are 2, side by side, on my 240D with 6 small hoses) and one hose was loose, not fitting snugly, so I replaced that. I noticed the small, crescent shaped levers, that actuate the valves, were both completely worn off at the pointed end. I replaced those, too. What a difference. The car has never shifted better. Hard to believe that the tiny clearance at the point of the lever would make a big change but did it ever! Unrelated to my vac problem, though, right?
As for the leak, I'm leaning toward the locking system. Wondering how long that reservoir should hold vacuum for the locks? I drive the car most days and the lock system works "as advertised", locking and unlocking all doors and the trunk. However, if it sits for a "while" (meaning days) it'll lose vacuum. More quickly in super cold weather (below freezing). Curious as to what to expect as far as "normal" leak down for a 40 year old car w/216K miles would be? My '97 300D seems to hold it "forever".
I've been putting off diving in to that system, but it might be time.....

The vacuum system was designed to hold 10 open close cycles of the door locks.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

Thanks for that info. Good to know!