I know I have some leak down of vacuum due to the reservoir only holding enough to run the locks for 12-24 hours; a typical final
Downshift clunk when coming to a stop (at shifts beautifully the rest of the time though), and only semi-operable middle AC vents.

Pulled all cabin consumers off and ran a test. For some reason I thought that 25” was the magic number. Going from idle to 2000 rpm adds maybe 1” of Hg.



I know that the 5-way splitter under hood is at least sufficiently hard that some of the lines slide in and out easily. So I have a new one on order. But this is without any of those consumers attached, at sea level, etc.

Just would appreciate thoughts on if I need to chase this down before chasing other things. I guess my first step should be to block off the other port from the manifold, if not the booster as well... but don’t want to take unnecessary steps...

Thanks!

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

A good vacuum pump normally creates around 18-20 inches of vacuum and it appears from your vacuum gauge that your pump is doing it’s job. I normally consider replacement of a vacuum pump based on miles on the pump. As far as I know rebuild kits for vacuum pumps are no longer available. As a maintenance item I replace the pump at around 200K miles. I have seen the catastrophic failure to an engine when the vacuum pump explodes internally.

You have sufficient vacuum to get everything to work properly after you take care of the leaks.

You might remover the Check Valve on the Vacuum Pump and take a look at it and hose it out with WD-40 (don't use anything like brake cleaner that softens plastic as there is plastic parts inside of the check valve). I was getting like 17 of vacuum and it turned out the Check Valve was full of gunk. Cleaning it out with WD-40 cured it and that was like 8 years or more ago.


Ebay shows that there are still expensive kits available but you need 2 kits and a new Check Valve to equal a rebuilt or new Vacuum Pump. It is cheaper to get the whole pump and you also get a warranty.

Other issues.
W123 - Vacuum Pump

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84 300D, 82 Volvo 244Gl Diesel

You have sufficient vacuum to get everything to work properly after you take care of the leaks.

You might remover the Check Valve on the Vacuum Pump and take a look at it and hose it out with WD-40 (don't use anything like brake cleaner that softens plastic as there is plastic parts inside of the check valve). I was getting like 17 inches Hg of vacuum and it turned out the Check Valve was full of gunk. Cleaning it out with WD-40 cured it and that was like 8 years or more ago.


Ebay shows that there are still expensive kits available but you need 2 kits and a new Check Valve to equal a rebuilt or new Vacuum Pump. It is cheaper to get the whole pump and you also get a warranty.

Other issues.
W123 - Vacuum Pump

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84 300D, 82 Volvo 244Gl Diesel