Electric Vacum pump
- Thread starter dbarilow
- Start date
Mr_Roboto
Full Access Member
Same thing, a diaphram type vacuum pump. The only difference is that when the diaphram wears out, it costs twice as much to replace the pump.
GenLightening
Yeah, it's a CHEVY!
It does say "a power brake booster needs at least 16 inches of vacuum at engine idle" so it makes at least that much (hopefully). What I want to know is what it's duty cycle is, since it also says "The electric vacuum pump kicks in when engine vacuum is too low", so it may not be designed for constant use on a diesel. But, like has happened before, I could be wrong!
These units are OEM in many mid 80's to mid90's GM products. they do work. The specs must be the same as our mech driven ones since there is no change in the booster design other than an additional hole for the on/off switch.
Muddinkev44
Full Access Member
i wish you would of showed this to me like 8 days ago......before i replaced mine....
OkieGringo
OkieGringo aka Baja
Go here for ELECTRIC VACUUM PUMP MODS: http://www.california.com/~eagle/figs/vacpump/vac.html
I had this exact unit. I have a van so finding a mounting place for it was a real challenge. I wound up mounting it under the cowl; the vibration in the cab was unacceptable. Also it never stopped running and for me it didn’t deliver amount of vacuum needed to make the booster work at the same level that a working IDI vacuum pump does. I sold the unit to a friend of nine who used it on his car, it worked on the car but you can still hear it when it runs…
I had replaced my standard vacuum pump twice in 12 months or so before trying the electric version. After trying the electric one I bought a “new” OEM IDI vacuum pump ($125, no core charge), drained the oil and refilled it with synthetic motor oil before installing it. I used synthetic motor oil because after disassembling the one that failed it seemed more like the piston that runs between the cam and diaphragm was sticking in the up position which reduces the vacuum. I cleaned the area with PB blaster and rinsed it several times with the synthetic oil before filling the cavity to within 1/8” of the top (I filled the new pump to the same level), the amount removed from the new pump was at least ¼” from the top.
Testing - Before removing the old pump I attached a vacuum gauge and the vacuum was under 10 at best. Once I removed the pump from the van I removed the vacuum dome from the drive portion of the pump. Next I checked the vacuum again by attaching the vacuum gauge and quickly compressing and released the piston going to the diaphragm with a wooden hammer handle. Again I found that I could get only about 10 inches of vacuum. After cleaning the piston area and lubricating with motor oil I was able to get and hold 21+ inches of vacuum.
I’ve only got about four months on the new pump so it’s too early to tell long term effects at this point.
I had replaced my standard vacuum pump twice in 12 months or so before trying the electric version. After trying the electric one I bought a “new” OEM IDI vacuum pump ($125, no core charge), drained the oil and refilled it with synthetic motor oil before installing it. I used synthetic motor oil because after disassembling the one that failed it seemed more like the piston that runs between the cam and diaphragm was sticking in the up position which reduces the vacuum. I cleaned the area with PB blaster and rinsed it several times with the synthetic oil before filling the cavity to within 1/8” of the top (I filled the new pump to the same level), the amount removed from the new pump was at least ¼” from the top.
Testing - Before removing the old pump I attached a vacuum gauge and the vacuum was under 10 at best. Once I removed the pump from the van I removed the vacuum dome from the drive portion of the pump. Next I checked the vacuum again by attaching the vacuum gauge and quickly compressing and released the piston going to the diaphragm with a wooden hammer handle. Again I found that I could get only about 10 inches of vacuum. After cleaning the piston area and lubricating with motor oil I was able to get and hold 21+ inches of vacuum.
I’ve only got about four months on the new pump so it’s too early to tell long term effects at this point.
TLBREWER
Windy B Ranch
Double the vacuum by switching to synthetic? Time to stir the pot some. How do the differences in vacuum effect the brake booster? I mean I understand how it all works. What I'm trying to say is, is there a limit as to how much vac will affect the booster/brake action. Or will increased vac keep lessening brake pedal "effort" to the point of gaining efficiency? I would suspect the answers to all these questions is no. But this may be yet another variable to throw into the discussion on brake master cylinders, pad material, ABS valves, hoses, etc. ,etc., etc.
Tom
Double the vacuum by switching to synthetic? Time to stir the pot some. How do the differences in vacuum effect the brake booster? I mean I understand how it all works. What I'm trying to say is, is there a limit as to how much vac will affect the booster/brake action. Or will increased vac keep lessening brake pedal "effort" to the point of gaining efficiency? I would suspect the answers to all these questions is no. But this may be yet another variable to throw into the discussion on brake master cylinders, pad material, ABS valves, hoses, etc. ,etc., etc.
Tom
It didn’t double the vacuum, I believe the piston or connecting rod that goes to the diaphragm gets sticky which reduces the amount of vacuum. The original lubricating fluid in the pump looked and smelled like non-synthetic 90 weight gear lube. There is nothing in the pump that limits the amount of vacuum other than the travel of the diaphragm. Once the unit gets to the 20’s (inches of vacuum) the piston or rod is lifted off the cam by the vacuum pressure itself. I believe, because the vacuum is usually at the maximum (20+ inches) the upper end of the piston gets very little lubrication during its life span due to the heavy weight of the original lubricant. By replacing the lubricant with lighter weight synthetic oil I believe it better lubricates and cleans the piston. I’ve checked the temp several times by putting my hand on the vacuum head and cam body after traveling more than an hour and it always feels warm but never hot so I don’t heat is an issue. All I can say is if you have lost vacuum but the diaphragm is good shape remove the vacuum head from the cam body clean the area around the piston and lubricate with synthetic oil and see if the vacuum improves, if it does then replace the oil in the cam body with 15w 50 and see if it works.
Vacuum by itself is no cure all, but new vacuum units produce 20+ inches vacuum so if you check your pump with a vacuum gauge and you’ve only got 15 inches or less start looking. I think there are several folks on here that have a “vacuum check” posted so just ask and they’ll point you in the right direction. Once you get through the vacuum test you should know if the pump, booster, or hoses are good then it’s on to the mechanicals…
TLBREWER
Windy B Ranch
Now I understand. Excellent tech tip.
Tom
Tom
When I filled My old VP with light weight oil I notice it would get hotter than when using the gear oil so I put gear oil in it again, now I do believe that LW oil will let the piston move with less friction at least until the oil gets warmer.
f-two-fiddy
Registered User
Maybe a light weight synthetic gear oil?
The oil I used was 10w 40, or 15w 50 Mobil synthetic. I’ve got the bottle on the shelf at home, a ways away from where I’m at right now. When I return around the 8th of Feb I’ll drop a note here. What do you mean by light weight oil hydraulic or ATF?
Like I said I've only got 4 months in on this, if it goes or I think it's running too hot and I go with a different oil i'll let you know that also...
Like I said I've only got 4 months in on this, if it goes or I think it's running too hot and I go with a different oil i'll let you know that also...
Last edited:
dbarilow
over worked
The pump will pull 23" of vacuum. The pump was designed for cycle duty unfortunately not for constant duty.
Per SSBC
Per SSBC
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