Vacum issues
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Vacum issues
Hey guys, need some help with vacum on a 85 6.9L
A few weeks ago I lost my forward clutches in my C6 so I had it rebuilt. Went to pick it up and my mechanic said my vacum pump was bad bc he was only getting 5in of pressure. Because of this the trans wouldnt shift preoperly. Drove the truck home and put on a new vacum pump. Fired the truck up, SAME PROBLEM!! I am getting 10in of vacum from the small hoses on top of the IP. Also, my climate control wont switch selections and my brake pedal is hard. The transmission will shift 1-2-3 before I get to 20mph. Any suggestions?? There is a little ball looking canister on top of the passanger side fender and a coffee can on the drivers fender, what are these for? Im wondering if there is something blocking the lines somewhere. I guess the only other possiblilty could be the new pump is bad..... Help please
A few weeks ago I lost my forward clutches in my C6 so I had it rebuilt. Went to pick it up and my mechanic said my vacum pump was bad bc he was only getting 5in of pressure. Because of this the trans wouldnt shift preoperly. Drove the truck home and put on a new vacum pump. Fired the truck up, SAME PROBLEM!! I am getting 10in of vacum from the small hoses on top of the IP. Also, my climate control wont switch selections and my brake pedal is hard. The transmission will shift 1-2-3 before I get to 20mph. Any suggestions?? There is a little ball looking canister on top of the passanger side fender and a coffee can on the drivers fender, what are these for? Im wondering if there is something blocking the lines somewhere. I guess the only other possiblilty could be the new pump is bad..... Help please
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I got 23" rite off the pump. Guess I have a leak somewhere. I even have 23" at the brake booster. Something isn't rite and I can't figure it out. Should I be getting the same readings on all of the vacuum lines???
Lead Driver
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Pull a reading from the vacuum tee, and start plugging off until you isolate the problem. Then its just good old fashioned follow the hose to see where the break / crack is. If yours is a cruise truck, check the vacuum switch on the brake pedal assembly. Ive had pretty rotten luck with those leaking. However it sounds like your leak is bigger.
Lead Driver
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I would maybe start with the line going to the back of the trans. Cap it and see what difference it makes. Could be the vrv or whatever its called is leaking. Also check the lines to the TPS thingy on the IP. other than that its just brake booster and dash vent stuff i believe.
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Do you have a diagram of the vacuum system? The 3 way T that is bolted to the firewall doesn't look rite. There is two nipples for the main vacuum hose (one coming from pump and one going to the brake booster on the other side of the T) and two smaller nipples. After taking this T off and looking inside, the holes in the T are the size of a pen head. Doesn't look like I could get the same amount of pressure through a small hole like that..
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Lead Driver
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keep in mind this is vacuum were dealing with here. There is no substantial airflow. The vacuum will stabilize throught the system in short order with no leaks. Also remember vacuum leaks will wear out a a vacuum pump.
As far as diagram, no i do not, but like i said before the lines should go from pump to tee. From tee: to trans modulator, to IP (for C6), to dash controls. Should be fairly easy to trace them. Especially if you isolate the problem at the tee, like i mentioned before. Also, make sure the tee is not cracked, ive seen it happen.
As far as diagram, no i do not, but like i said before the lines should go from pump to tee. From tee: to trans modulator, to IP (for C6), to dash controls. Should be fairly easy to trace them. Especially if you isolate the problem at the tee, like i mentioned before. Also, make sure the tee is not cracked, ive seen it happen.
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im getting 23" from the big hose that comes off the pump and 23" at the brake booster (same big hose after the vacuum tree). ALL of the smaller hoses are reading 10". I know im beating this into the ground but I dont understand how the same amount of pressure can pass through a hole the size of a pen head and a hole that is 1/4" around. And to back it up they are ALL reading 10"????
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It appears to be the brake booster. Took the hose off the booster, plugged it, and got 22" on all other hoses. So, its eaither the diapram has ruptured or the check valve is not functioning properly.... What fun this
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