Diesel fitter

Wow I Haven't posted on hear in a very long time!

While towing my 5er the other day I started hearing a hissing sound, (seems to be near the brake booster) this did not affect my engine performance or brake performance. I did notice that I could change the sound by slightly turning the wheel or lightly stepping on the brake pedal. Sounds like some kind of vacuum leak, but doesn't this have a hydroboost system? Seems loudest coming right out of the pushrod area from under the dash.

Anyone else run into this before? I hope it is considered part of the power train warranty?

Thanks in advance!

willym

Apparently (as I've read on other forums) there is a hose going to the brake hydroboost cylinder near the firewall that has a liner that gets loose and causes a hissing like noise as it restricts the oil flow. This may be your problem. Do a search here or on the Cummins forum for more info.

BigIron70

Replace the high pressure p/s hose from pump to hydro boost. Orifice tube inside hose breaks, causing noise in p/s system. easy to check remove the p/s line at booster top line. If the white plastic tube is stuck in the metal line then it has broken and needs to be replaced.

Diesel fitter

Thanks for the replies! Great info I will check that out thanks again!!!

RocknRick

I guess it's my turn! Saturday I was cruising down the road and all of the sudden heard the dreaded "hissing" sound. It was like a vacuum line leaking. After 1 Google search amazingly DTR popped up with the answer. I just wanted to let everyone know how much I appreciate the communication on this Forum. I went from WT?, to replace the high pressure p/s hose. The new part# 68035282AF for the lower hose and part# 68080207AD for the upper hose, which is the hose with the plastic tube causing the hissing. Both hoses have had engineering changes, so I replaced them both. I hope the engineers got it right this time. Thanks Again
Rick

Diesel fitter

Well the hose made it a little over 2 years then failed again! So much for mopar fixing a design issue! Time for another $100 hose, I guess it could be worse!

Kenneth Mccall

I have 2009 cummins. My question pertains to the metal brake tube that enters the too of the hydraboost. Originally I had a small leak around the high pressure hose fitting coming from the power steering pump (at the power steering pump). I replaced the hoseand everythig seemed fine.

Later I started having the hissing sound, checked to see if it was the hose liner but the hose was intact. I replaced the hydra boost and that seemed to reduce the noise by about 50%, but about a month later a leak developed around the high pressure tube where it entered the hydraboost. When I removed the tube I found a hairline crack around the seating flange of the brake tube. I replaced the tube and everything seemed ok, no leak but still a little noisy until about 2 weeks later ... ling story short, I have now either replaced the tube myself or had a good diesel mechanic replace it 4 times total and the tube still continues to crack at the seating flange.
Has anyone else encountered this issue?
Is it common?
What is the cause?