squirlchasr919

Alright guys I've had this problem fro awhile now and decided enough is enough. When it's cold outside, talking below 50, my ebrake light and abs light will come on if I adjust the direction of airflow on the dash ****, or the cruise control is turned on or it speeds up when climbing a grade.
Also when I am comming to a stop if I put the truck in neutral my brakes get 10 times better. Same thing if I go from neutral to drive at a stop, the pedal will drop down about three more inches.
The only thing I can figure is I'm loosing vacum somewhere right? I mean the brakes need a vacum to work and so does the dash **** and the cruise control. How would I go about finding the leak?
I tought diesels didn't even make enough vacum to support powerbrakes, so is there a vacum pump somewhere that might be wearing out?

condensr

Yep, there is a vacuum pump. It's attached to the power steering pump.

Are you losing a lot of engine oil? A vacuum leak will commonly cause this, as the air output of the vacuum pump goes in to the crankcase. If there's just a vacuum leak, that will cause crankcase pressurization and excess blowby.

If it's just a weak vacuum pump, you might not notice any oil loss.

squirlchasr919

I hadn't noticed an excessive amount of oil loss, I'l pay closer attention to it now to be sure. But how would the output from the vacuum pump go into the motor? From looking in my manual I saw the pump and it has an oil supply line but I really don't see how it would get into the motor. Especially in the case of a leak, it seems like any excess vacuum created by the pump would using the same leak that was already there.
In any case how can I determine where the leak is or if the leak is the pump itself?

infidel

I use a hand vacuum pump with gauge to run down leaks. Most autoparts sell them for bleeding brakes.

Most common vacuum leak source is the line to the cruise control actuator under the driver's side battery. Battery acid eats the line.

The reason a vacuum leak causes oil usage is because when there is a leak the vacuum pump basically turns into a compressor pressurizing the crankcase and causing more blowby. This is because the vacuum pump exhausts into the crankcase, no leaks, no exhaust.

Cowhand

Check the big fat hose that goes from the vac pump to the brake booster. I've found the fitting at the pump loose, as well as the small line that tees off the big one leaking as well. The small teed line supplies the vacuum for all the dash controls.....

vssman

There was a recall on the vacuum pump to add a check valve to the side of the pump. This was to keep the oil lubed pump from letting oil escape into the rubber lines. Check the big line exiting the vac pump for softness. Also most of the other lines are plastic but still have rubber connectors. Those also swell when exposed to oil. The check valve is part of the hose nipple that the rubber hose attaches to at the vac pump. If it was replaced, it would require a larger socket to remove than the non-check valve nipple. I don't know the different dimensions but I think the non-check valve would need something like a 1/2" socket. Keep in mind, although rare, that just because it was taken in to get this recall fixed the check valve may not have been installed - as was in my case. Dealer went out of business so I guess I can't go back and complain.

Fishinghaoliboy

I just went though a problem with the brake light on and also the abs light on after a rebuild of the brakes by a shop. Not my truck but had to step in after $1100 dollars and brakes still did not work. They put in 2 vacuum boosters and couldn't find the problem. As someone stated earlier in this thread get a vacuum pump from your parts store, looks like plier handles and a vacuum gauge with a hose for making connections. I also got a universal vacuum connector from NAPA and also a universal T also at NAPA and picked up 5 pieces of vacuum hose from 1/8" up to 1/2" I think. The tees and hoses cost $7 and change. Start by disconnecting the line from the T in the line from the vacuum pump to the brake booster and connect your vacuum gauge and start the truck. See how much vacuum you have with the truck running. Mine was about 26 inches of vacuum. This is normal/good/adequate. If you have a reading like this shut the truck off and watch the vacuum gauge and see if it drops with the truck shut off. If should hold steady at this setting and not show a measurable drop. If it holds then your vacuum pump and booster are OK and don't need to be changed. Then reconnect the line to this tee, insert the tee you purchased and your vacuum gauge/pump and repeat the test of starting the truck and checking the vacuum that the pump produces. It again should be in the 26 inch range and should hold when engine is shut down. If it does not then follow it up to the dash above the vacuum booster and you will see where it branches into multiple lines. Disconnect either end of this branching of lines and again connect your vacuum gauge and start the engine again. Continue testing individual lines until you find the leak. With you vacuum gauge/pump you can connect to each individual vacuum line and pump up vacuum with your hand pump and see if each line holds pressure. When you find the one that does not follow it to the end and you will find your leak. The leak on my buddies truck was at the back of the engine. The branching of vacuum lines sends a line off to the passenger side of the truck and right behind the valve cover it has an elbow and goes down behind the engine to the top of the transmission. This is a hard plastic line and with vibration it had broken right next to the 90 degree angle connecter. This supplies vacuum to the shift controller for 4 wheel drive. Hope this helps?