Anyone tell me how much vac this motor is supposed to pull on hot idle in park?

I resealed mine and my gauge still isn't reading correct in the vehicle, so I'm not sure if I have a vac leak or the gauge is just off.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Hey, HitMan.
My '91 pulls 16 inches mercury on my mighty vac under idle conditions you described (warm and approx 700 rpm). This seems a bit low, but I sure can't find any vacuum leaks, and this number is constant and repeatable..
I can't remember what the dash vacuum guage in the car reads at warm idle. I'll check it when the wife gets home.

DG

I was getting around 15-16 at idle when I checked earlier. Maybe my gauge is off or is normal. It had been over six months since I drove the car so I can't recall where the blasted needle pointed. I tore the top end apart to reseal and fix ever leak. Every piece of rubber I can find has been replaced.

Eagerly awaiting your reply!

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Okay, I checked it out.
Mine is a '91 300SE, so should be same setup.
At warm idle in neutral, approx 750 rpm, the vacuum gauge is
almost pegged, less than 1/10 inch from the peg, maybe 0.050".
If I increase rpm just a tad, say 850, the needle slides over and hits the peg.
As I said, mine runs about 16 on the mighty vac, so I can assume that the gauge pegs about 17 " mercury?

Cheers,
DG

Well I found a large leak today on mine. The Y fitting from the manifold tit to the climate and gauge hose fell off after just touching it! So, I fixed that and picked up nearly 2" of vac at idle

Now I have around 17.5" at idle, very steady too. I'm getting pretty excited now. When I would blip my throttle it seemed to take right around 20" to peg my gauge.

17.5-18" is just about on the needle as you describe.

I have a few more connectors to check here probably tomorrow. Hopefully I'll get this resolved. Yet, it's 100% livable even if this is as good as it gets. Then next week comes precat gutting and new flex discs with center bearing.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Where are you measuring the vacuum from and what do you mean "pegged?" At the left side of the dash gauge or the right side?

__________________
1991 300 SEL
218,000 Km

"Xsbank's rules of mechanical intervention: Always go for the easiest solution first; 90% of what ails a gasoline engine is ignition; After that its all a WAG."

My vacuum gauge has about 1/4 to 1/5th of the way to go to the peg so it looks like I have a leak also... well, when it stops raining...

__________________
1991 300 SEL
218,000 Km

"Xsbank's rules of mechanical intervention: Always go for the easiest solution first; 90% of what ails a gasoline engine is ignition; After that its all a WAG."

Found a vacuum hose that was cut and leaking - cut the end off with scissors and stuck it back on but no change to the gauge.

At idle and you step on the brakes, the gauge moves to the right, but when I take my foot off, the gauge doesn't move right back - anyone know what gives? Is the vacuum vented to the air when you remove your foot? Why won't the gauge move again?

__________________
1991 300 SEL
218,000 Km

"Xsbank's rules of mechanical intervention: Always go for the easiest solution first; 90% of what ails a gasoline engine is ignition; After that its all a WAG."

You lucky Devil; I kept Old Pearl today, and it was sitting in the garage, still warm after an errand.
I checked the vacuum/brake thing.
At warm idle in Park, the Vacuum needle is 95% to the left, or almost full vacuum on the gauge. When I step on the brake, nothing happens - the gauge does not move. I can push really hard - nothing. When I let off the pedal, no vacuum change, it holds continually at 95%.

Sounds like you may have a brake booster issue?
If it's leaking a bit when depressed, it may not recover quickly, or may not recover completely until you blip the throttle to obtain really strong vacuum.

DG

Hrm. I suppose I can disconnect the booster, plug the hole, and check vac. But it seems maybe the M103 doesn't generate huge idle vac?

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Update:



54-255 in the FSM shows full left peg is 0.585bar... converted to inches of merc, and came up with 17.32"

0.4-0.6bar (11.85-17.77") is within the factory specs, so it seems my motor is sealed up!

Hope this helps...

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Lots of good info on this thread!

My car shows the proper vacuum at idle while in park (needle all the way to the left), but as soon as I put the car in gear, the needle jumps to 3/4? I'm assuming this isn't normal? Thanks.

__________________
Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

Sounds right, get a vac gauge and I'll tell you what mine reads if you need.



Mine has been running quite well, starting is just a bit off still

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]