Lil Dog

Just happened tonight coming home. I had to hit the binders for some quick lane changer in front of me. Anyhow, just after that now my brake pedal/hydroboost is hissing whenever the steering is at center or you have no load on the brakes. Also now the pedal has slow to react when you first hit it, the boost comes on slower. Sounds like there is something stuck in the bypass valve. The fluid seems good still as its only got 15,000 km on it.

Sure, just get happy with my ME conversion and I probably have to get to the dealer for this... Any suggestions?

Lil Dog

Checked the fluid level and it was fine, still smelled like clean ATF.

Called dealer that I trust and the tech there said with the combination of steering and braking at the same time, it could be an air bubble in the hydroboost that will work its way out. I hope so, its annoying.

Jim W

See my response in TDR.

Lil Dog

I did Jim, thanks.

Lil Dog

Today I went to town on the system doing full lock to lock turns with the steering and holding the brakes to full travel and releasing quickly to get the flow and bypass to cycle.

The good news, its gone away, sort of.. Now if I tap the brake pedal slightly, it goes away. IF, I pull back on the pedal with my foot, it comes back.. So now I have narrowed it down to the booster, just why is it hissing when I pull the pedal fully back?

Input please... Thanks.

Jim W

I believe (I am retired hydraulic engineer) that the booster which is an amplifier may have an issue with the relief valve in it. Most booster have a relieve valve built in to prevent over pressurization of the brake fluid. This may have a tiny piece of debris sticking in the relief valve or the valve has malfunction. From the panic stop that you preformed. This will cause a hissing sound as oil is pass thru the valve. This should be normally closed unless pressure is to high, then will open and maintain the proper operating pressure.
I would suggest replacing the booster as the relief valve is not serviceable. At least I have never been able to find a relief valve for one before.
Good luck.

Lil Dog

That sounds like the problem. THanks Jim.. I will have to book in the truck for some service.

mega-engr

That stinks. Let us know how you handle it. Maybe you can leave you stuff as is since it is not "related". It would certainly suck to have to revert and then re-revert to where you are now for such a thing.

By the way, did 300 miles of towing with the set-up and had no issues, ran like a champ, drove 65 to 70 the whole way and have 11.5 mpg on my overhead! Heck ya. Still need to get those gauges though, maybe I will cut some real gauge corners and at least get an insight to plug in... Had the watchdog and it was a POS in my opinion, returned it...

Lil Dog

Thanks Mega.

From another site I frequent, some Dodge technitions offered up some possible sollutions. Apparently the pressure lines are lined with a teflon tubing and it sometimes gets pushed into the booster cylinder.

I pulled it out today and found it to be flared and worn like it has been rubbing in there on something, just as these guys told me. Got all giddy thinking I had it fixed, but 10 minutes into my drive, it started to hiss again. This time not as loud and I could not get it to temporarily stop like I did before by tapping the brake pedal. Maybe a small piece of that teflon is stuck in the booster somewhere??? Dunno..

Here is what I found..

mega-engr

A couple of months ago, I had to replace the booster in my Mom's GMC Jimmy (a 97 with only 60K miles). There was hissing noise and not much "boost" helping out. Needed a lot of force to stop it and it scared me to think of my Mom driving it that way for a bit... Anyway, I'm glad it was the booster that was the issue as replacing it solved it and it was actually easier than I thought. Getting to the bolts inside at the firewall was the trickiest because of the tight spaces. Beside body contortion a swivel on the socket did the trick. If your truck is under warantee, it sure would be nice to get it taken care of and ignore the motor stuff.

Lil Dog

So being frugal, I just trimmed the tubing about 1/2" sticking out of the tubing and put it back in. Drove it for 2 days and now it starts to hiss again. I pulled the fitting apart to look see and its the same failure.. The tubing is creeping in the hose. I have a new hose ordered for it, ~$100 or I reassemble for them to do it under warranty.. I need the truck today, so I might just bite the bullet for the $100..


Here is todays tubing, hard to tell the difference..

Smiley1206

Lil Dog I have a 2004 with the same noise. Replaced the power steering pump and hydroboost 3 times and still has the noise. REplaced the High pressure hose from the booster to the gear box? Any ideas? I've replaced what the local dodge dealer told me too. I'm out 1500 so far

mega-engr

So what happened? Resolved itself?

Smiley1206

Which hose did you replace? From the pumpo to the booster or the booster to the gearbox?

Lil Dog

OK guys here is the last update.

About 2 weeks ago I replaced the high pressure hose from the pump to the fitting to the hydroboost. (Time constraints etc.) The teflon tubing is supposed to be embedded or locked into the rubber part of the hose. So from what I can tell, from my sudden steer and brake I popped it loose. It pushed out of the hose and through the steel fitting right into the hydroboost. That tubing was pushed about 7 inches through the steel tubing to get there. So trimming it was futile as its not supposed to be there to begin with. I should have known it was wrong when I pulled the fitting apart at the booster from the hose to the steel line and there was teflon tubing connecting them.... Not normal...

All said and done, they wouldn't warranty the hose unless they changed it on a service. So I paid $90 for the hose and did it myself since I had it apart already anyway. Problem solved. All I can say is that the 2 Dodge techs on the TDR diagnosed the problem in about 2 minutes over the message boards, local dealer....not so good.

Hope that helps anyone who is experiencing a hiss in the system.