| Re: [GMCnet] vacuum assist - again [message #75689] |
Thu, 04 March 2010 20:56 |
Gary Casey
Messages: 448
Registered: September 2009
Karma: 0
|
Senior Member |
|
|
I'll pipe in here, but I think it has been covered fairly well. Except that the built-in reservoir in the booster will allow a "few" brake applications - certainly more than one, although it depends on how severely the brakes are applied. It would certainly be a bad idea to pump the brakes to bring the vehicle to a stop after the engine failed. Adding an additional reservoir will increase the number of brake applications available, and adding a vacuum pump will allow an indefinite number of applications. However, as some have said, providing good maintenance of the production system might be the best - and simplest - approach. If I were adding a vacuum pump I would put it in parallel with the engine. Yes, it could be plumbed in series, but why pump the output into the engine? No reason to. With a reservoir installed that has a check valve leading to the engine and another leading to the pump, the one in the brake booster is essentially
irrelevant. Unless you are concerned about a failure of the tank. Another comment - yes, when driving in the mountains it might take more than one or two brake applications to stop after an engine failure. However, the engine will likely not stop turning (don't put the transmission in neutral!!) and as long as the engine is turning it will keep producing enough vacuum to work the brakes. It would be good to manually downshift just to increase the engine rpm and the vacuum generated.
After the engine has been shut off for a while (at least a few days) I often will check the integrity of the vacuum booster by applying the brakes. The vacuum ought to last for at least three applications. Mine has been sitting for a couple of months and it still held vacuum. It should hold for a long time.
Gary Casey
Obviously I agree With Emery. The vacuum pumps off old cars are getting old becoming unreliable. Jim K does have one that is new and will do the job. I used 3 units from old cars and all of them failed over a period of time. I bought a heavy duty one from Stainless Steel Brakes that has a separate vacuum sensor from the pump. Two of those sensors broke and there is no indication of the failure so I decided to tie the pump in parallel with the auto vacuum line using a small tank with a built in check valve and operating it with a switch. The most critical time for engine dying is if you are going up a mountain. Without a vacuum pump you have one pump of the brakes and then you are on your own. Like the cars that have unintended acceleration, put the brake on hard and keep it there. I don't consider it a bad idea since I can test it at any time and it is a lot safer than not having a second vacuum source. The vacuum tank is just suspenders.
--
Gene Dotson
74 Canyonlands
www.bdub.net/Motorhome_Enhancements
New Windows and Aluminum Radiators
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
