Vacuum Leak on 6.5L TD

[jeff4re]

The Air Vent controls inside the vehicle have stopped working. It appears the Vacuum line that controls these vents has no vacuum. I've also noticed the motor is running rough with more black exhaust than normal. Is the Vacuum Pump typically replaced after a period of time? Could the Emision System be causing the problem? Is there a way I can test the Vacuum system? Thanks for your assistance.

Jeff

[Mainous]

What year is your truck?

[Hye]

My A/C vents run on electric motors. What year?
Black smoke could be vaccuum pump related. Waste gate is vaccuum operated. No vaccuum = black smoke at hwy speed or when accelerating.
Sometimes the pump comes and goes before it completely quits. Find the hose coming from the pump, disconnect and put your finger on the open end. With the engine running, it will hold your finger pretty tight. On mine, the easy place to test is at the wastegate controller electric valve on top of the driver side valve cover. Be sure to put it back together just like you found it. Don't reverse the hoses.
My '94 is now on its third pump. I replaced the original pump at 187,000 with a Lucas pump that lasted 90,000 more. Replaced that one with O'Reilly rebuilt, 'cause that's what I could find the weekend I fixed it. Takes a puller commonly used on P/S pumps to remove/replace the pulley. Be careful about pulley alignment or you'll be replacing the belt soon.

[jeff4re]

The Truck is a 98 AM General Hummer 4dr Wagon. I've disconnected the vacuum hose coming from the pump and covered it with my finger. I felt a very slight suction. I asume the suction should be much stronger.

[moondoggie]

Good Day!

"The Air Vent controls inside the vehicle have stopped working. It appears the Vacuum line that controls these vents has no vacuum." "I've disconnected the vacuum hose coming from the pump and covered it with my finger. I felt a very slight suction." Ask your friends that work on their own vehicles. One of them is likely to still have a vacuum/pressure gauge or vacuum gauge lying around. They used to be used extensively to troubleshoot engine problems, many years ago. The vacuum pump should produce > 20" of vacuum when dead-headed into a vacuum gauge.

"I've also noticed the motor is running rough with more black exhaust than normal." Does your engine have a turbocharger? If not, vacuum has no relationship to this problem. If it does, vacuum would have nothing to do with rough running, but certainly could be involved in black smoke. Black smoke, on a turbocharged engine, is virtually always caused by lack of boost. Boost on a turbocharged 6.5L has I think been controlled by vacuum since 1994 in the Suburbans & pickups; I have no idea if this is so on your Hummer. There's a brief summary of how this system works at crack in line from wastegate seliniod (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=004746#000003) (Click in colored text.). You might want to look at my 23 Jan 04 post in Wastegate Solenoid Question (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=005667#000003) (Click on the colored text.).

You might want to click on "my profile" & let us know what year, etc. truck you are talking about. It's handy, because you don't have to remember to do it, it shows up at the bottom of all your posts automatically. smile.gif

Blessings!

Brian Johnson, #5044

[jeff4re]

Thanks for all your help...I've replaced the Vacuum Pump and the truck is running great.