Vacuum wipers barely work

bigd1101

bigd1101

Senior Member
The vacuum wipers on the 53 Merc barely work. They worked better before the engine overhaul and teapot rebuild. I really think I have a leak somewhere and why I cannot get this car to run a smooth as I want. There is no consistency to this cars ability to idle right or without some kind of vibration. I clamped all the hoses I could find throughout the car, but I did find one hose off a T under the dash.

There are 3 hoses connected to the wiper switch, but this stray hose isn't long enough to reach the switch. There looks like a place for another hose on the switch, I'm not sure. I plugged the stray hose with my finger to see if the idle improved or if the wipers worked better, but no difference.

Don
 
It does sound like you have a vacuum leak somewhere. Check on You Tube for a video on how to check for vacuum leaks using a small bottle of propane.

Does your car have the dual diaphragm fuel pump? I thought the vacuum diaphragm half of the pump supplied the vacuum for the windshield wipers on your model. If so, maybe there is an issue with the fuel/vacuum pump. Though this would not explain the rough idle and vibration complaints.

Good luck with your search.
 
Your wiper / washer switch:

Your wiper /washer switch serves two purposes. When you turn the handle clockwise or counter clockwise, a cable (represented in the pictures by the red wire) between the switch and the wiper, either pulls the lever open or pushes it closed, turning you wipers on and off, and controls the speed of the wipers, depending on how much you turn it.

The two metal pipes coming out of the back of the wiper switch, have rubber hoses, going to the washer bottle, controls your windshield washers. To activate them, you push on the Silver spring loaded button, on the front center of the wiper switch handle.
 

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Zeke3 said:
It does sound like you have a vacuum leak somewhere. Check on You Tube for a video on how to check for vacuum leaks using a small bottle of propane.

Does your car have the dual diaphragm fuel pump? I thought the vacuum diaphragm half of the pump supplied the vacuum for the windshield wipers on your model. If so, maybe there is an issue with the fuel/vacuum pump. Though this would not explain the rough idle and vibration complaints.

Good luck with your search.
Click to expand...

FYI: Pump picture, arrows show wiper/washer vacuum lines
 

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Do you have power brakes, if so a leak in the vacuum system or the storage tank will greatly reduce your vacuum.
 

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Merc Cruzer said:
Do you have power brakes, if so a leak in the vacuum system or the storage tank will greatly reduce your vacuum.
Click to expand...

New power brakes. All seems to be tight. Adjusted the two gas/air mix screws as I didn't when I got the carb rebuild back. Seems to have smoothed the rough idle out. Still not sure where the disconnected hose goes under the dash. The wipers creep up sloooooowly and won't return, so there is some kind of leak or poor pressure to them. They worked great before the engine overhaul. I have a feeling the new power brake system is robbing the wipers of vacuum.


How hard is it to get to that wiper motor? I think that is where the disconnected hose might go...
 
bigd1101 said:
New power brakes. All seems to be tight. Adjusted the two gas/air mix screws as I didn't when I got the carb rebuild back. Seems to have smoothed the rough idle out. Still not sure where the disconnected hose goes under the dash. The wipers creep up sloooooowly and won't return, so there is some kind of leak or poor pressure to them. They worked great before the engine overhaul. I have a feeling the new power brake system is robbing the wipers of vacuum.


How hard is it to get to that wiper motor? I think that is where the disconnected hose might go...
Click to expand...

If you are 20 years old not hard!:) Or if the front seat is removed - not hard.;) Otherwise, it is above the radio, at the top of the dash. You said they "barely work", so that tells you they are are hooked up, just not getting enough vacuum. Make sure the switch is fully turned on. Either clockwise or counter clockwise. You might also want to take the wiper arms off, since the wiper blades create allot of drag, unless you are squirting the hose on the windshield while they are working.
 
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You might want to put a small amount of ATF in the vacuum motor to soften up any internal rubber parts. Not too sure on modern wiper motors though.
 
most vac. wiper motors put vac. to the motor when "off" to keep the wipers from moving causd by air flow over the windshield. leak in wiper motor valve? also disconnect or plug all vac. lines to get engine running correctly then reconnect one at a time to narrow problem down.
 
Since we know your wipers "barley work", we know the disconnected vacuum line under the dash, doesn't go to the wiper motor.

Test the windshield washer to see it it works. If not it could be the feed for them.

Another possibility is the heater plenum, has a vacuum line that controls the on and off valve for the water going into the heater core.
 

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Merc Cruzer said:
Since we know your wipers "barley work", we know the disconnected vacuum line under the dash, doesn't go to the wiper motor.

Test the windshield washer to see it it works. If not it could be the feed for them.

Another possibility is the heater plenum, has a vacuum line that controls the on and off valve for the water going into the heater core.
Click to expand...

There hasn't been wiper fluid in this car for years......and I did try looping the lines together in case that was it, but like I said, they worked great before the engine and carb overhaul. I did use some penetrating oil at the switch and where that cable goes into the motor, after contorting my old body into a pretzel. Not much if any improvement...
 
Talked to the guy who rebuilt the engine. He says that the wiper problem could be the PVC valve I had put on. It's a wide open constant draw of vacuum. I might try putting the old block vent tube back on to see if that helps.....
 
bigd1101 said:
Talked to the guy who rebuilt the engine. He says that the wiper problem could be the PVC valve I had put on. It's a wide open constant draw of vacuum. I might try putting the old block vent tube back on to see if that helps.....
Click to expand...

I will be interested to know if that works.
 
bigd1101 said:
Talked to the guy who rebuilt the engine. He says that the wiper problem could be the PVC valve I had put on. It's a wide open constant draw of vacuum. I might try putting the old block vent tube back on to see if that helps.....
Click to expand...

Just wondering, what does the PCV valve look like, when installed on your 53' Merc?

royd13483@aol.com
 
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