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Wayne64 wrote:Today we had a break in the weather and I drove over for my inspection. The wipers do not work and before driving over I ran a test. The truck is taking vacuum off the manifold since I'm using an electric fuel pump. I'm getting 18" at the manifold and upon disconnecting the first rubber line the truck almost stalled from the major vacuum leak. I put a vacuum gauge on the line right at the drivers side wiper motor and only had about 1" of vacuum. I dont think I have a leak but maybe a blockage somewhere. Any ideas or a problem area I should check? Thanks much

Sounds about right, much vacuum loss can be expected in that much distance & only the small tube.

MSeriesRebuild wrote:

Wayne64 wrote:Today we had a break in the weather and I drove over for my inspection. The wipers do not work and before driving over I ran a test. The truck is taking vacuum off the manifold since I'm using an electric fuel pump. I'm getting 18" at the manifold and upon disconnecting the first rubber line the truck almost stalled from the major vacuum leak. I put a vacuum gauge on the line right at the drivers side wiper motor and only had about 1" of vacuum. I dont think I have a leak but maybe a blockage somewhere. Any ideas or a problem area I should check? Thanks much

Sounds about right, much vacuum loss can be expected in that much distance & only the small tube.

Charles, maybe I didn't explain it right. Right side wiper disconnected and the steel line plugged. Left wiper disconnected and a vacuum gauge on the steel tee. Engine running with 18" at manifold and 1" at windshield tee. I can not see, not having 18" in cab unless either a line had a real bad leak or a line is plugged? It's too nasty to play with it for a while I just thought there might be a problem area to zero in on.

Most likely this is not the cause of your problem, but several times I have had to clear hardened mud from the steel lines of trucks that had set idle for a long time with the rubber hose broken or removed, a very small wasp like insect had deposited it in the line when laying eggs. I fished it out with a piece of mild steel tie wire and then blew the disconnected line out with compressed air.

Certainly a blockage is a possibility. What I was getting at though is you lose vacuum due to the small line ID. The farther away from the source you are, the lower the reading will be. Works sort of like air pressure, say 70 psi at the source, add a 50' hose & check the pressure at the far end of the 50' hose. Pressure will only be half as much or even less in many cases.

Thanks Gents, I ordered a roll of 7/32 vacuum line and will check to see if the steel lines are clear and replace the rubber hoses. At which point see if the wipers work.