Hard braking causes hard pull to the right

[The_Handier_Man1]

From: Colin  (Original Message)
Sent: 5/20/2003 1:00 PM

After making some changes, I took the old gal on a shakedown trip from Denver up to the continental divide and back. It seemed to have more power. The Winnie did 45mph up the final grade as opposed to the 15mph it usually does I don't know if it was really due to the changes I made or if it was because I was running without my normal load of five people and all their stuff. For those of you who are aware of my experiment with air injection, I couldn't really tell that it helped much. I'm working on my next design.

Coming down from the divide however, I had a problem with the brakes. I had good pedal and stopping power, but when I braked hard the Winnie would veer to the right. I had the brakes done about a year ago. I don't notice this problem when I am driving on the flats. I'm not too familiar with brake repairs, I have always left those to the professionals. I have a D22 on an M400 frame, drum brakes all around with the dual power boosters. Can anyone offer some advice for this problem?

Also, I was wondering about an auxiliary fuel pump. I know that some people swear by them for mountain trips. Do they really make a difference? I've heard that there is a drop in fuel pressure at lower RPM's

Thanks for your advice.

C.



From: denison
Sent: 5/20/2003 9:03 PM

I suspect one of your boosters. My 72 M400 D22 has the dual brake system, where one half of the system operates on one front wheel and the top wheel cylinders on the rear axle, the other system operates the other front wheel and the bottom wheel cylinders on the rear axle. It sounds like one of your boosters is a slacker - either stuck with goo, or having a leaking air bladder, or a sticking magic hydraulic valve, etc. For years I have been putting off rebuilding my boosters or having them done, because of the cost. If it veered to the right, you could follow the lines from the left front wheel back and see which booster it is that might not be doing its half of the work. You could try bleeding from the boosters, and seeing if what comes out is the same color. If one is a lot dirtier, I would think of getting both rebuilt. And bleed the rest of the brakes, to make sure there isn't water in there to be boiling. Of course it might be some other problem inside the drums, and a close visual inspection might reveal what it was. You do this by taking the brake drums off! !! Not much harder than digging a swimming pool with hand tools. Could it be a front wheel bearing that was loose on one side? If it was grease or oil getting onto the shoes on one side, they would grab/shudder at low speeds, and it would be there at all braking pressures. Linings have been known to fracture and slide around some, fouling things up. good luck and let us know what you find. I just have the mechanical fuel pump, and aside from changing filters as required, and putting heat shields between the exhaust system and the fuel line, and between the exhaust pipe and the front fuel tank, I had no fuel pressure problems going over that divide, in August. I also mounted my carburetor on a 1/4 inch plastic riser, to keep it from the worst heat of the intake manifold. denison.



From: mightybooboo
Sent: 5/21/2003 12:22 AM

{The Winnie did 45mph up the final grade Also, I was wondering about an auxiliary fuel pump}

Sounds like your fuel delivery system is working just fine.I have the extra fuel pump because i was fuel starved and it works for that,45 mph up the grade sounds normal,see no need for the aux. pump.
Boo



From: james
Sent: 5/21/2003 6:29 AM

Denison hit your brakes dead center,,, I just sold a rig with an Aux. gas pump. it was installed to keep the Gen. running under heavy engine load.A Note... you got it going up hill really well.... Down hill ,well ,Take it easy,, long grades 6 or 7% you need to stay under 35 ,, The load, Gravity and those old Drum brakes can't stand the heat....
Quote My Dad,,, always go down the hill at the same speed you went up or less... (he was a trucker in the 50's and 60's)
James



From: WinnieNMe
Sent: 5/21/2003 10:47 AM

WinnieNMe have had some practice out here in the Rockies with some steep grades. We have two fuel pumps. And of course we have to remember that I haven't a clue what I am doing, so it is all in her hands. except that , like James said, when we head up the hill,the aux pum goes on, and when we head down the hill, we go into usually 1st gear , and keep our foot off the brake as much as possible. And believe me some of these are ya hootie passes,( ya know wylie coyote, over the side, of the mountain type,) Red Mountain comes to mind. Right Colin?



From: Colin
Sent: 5/21/2003 5:14 PM

Thanks to all. I'll start checking the brake boosters. I actually found a shop here in Denver that has a rebuilt booster for $160. Question: When I push down on the brake pedal, I hear the inrush of air at the breather, and the vacuum reading goes down a little. But when I push the pedal down to the metal, so to speak, I still hear the air flow at the breather. If the piston inside the booster is pushed all the way in, shouldn't the vacuum flow stop? That is what was also making me think that something was wrong with the boosters. If that is a problem, what does that indicate as to where the problem might be?

C. 



From: denison
Sent: 5/21/2003 9:01 PM

On mine there is only a whoosh when the pedal is actually moving downward. Once down, no matter how hard the pedal force I am maintaining, the whoosh stops, and my manifold vacuum reading pops back to the normal, which is high when you are coasting along with the throttle shut. The whoosh is atmospheric pressure air being admitted to one side of the air bladder of both boosters. With brakes off, both sides of the bladder have an equal vacuum on them. It definitely sounds like a leak - of air - or of vacuum. If that price is for a rebuilt Bendix Hydrovac - it is a bargain. And its usually a good idea to replace them both - they are equally ancient. I came down hill into Denver in 2nd or 1st, depending on the grade. 



From: Colin
Sent: 5/22/2003 10:33 PM

I got under the winnie and listened while my son pushed down on the brake pedal.  I definitely heard a wooshing sound from one booster that I was not hearing from the other one.  I used some soapy water but found no leaks to the outside, must be an internal one.  Does anyone know if some outfit might still sell a rebuild kit for the Bendix Hydrovac?



From: denison
Sent: 5/23/2003 7:21 AM

Someone must sell the rebuild kit, or the rebuilders wouldnt be able to sell you rebuilts. If you find a source, let the rest of us know. These are items that may be unavailable this month, but in a few months they may have been cranked out, and be in stock somewhere. denison



From: melyash
Sent: 5/27/2003 11:02 AM

Since your looking at vacum you might not see any bubbles or indication of a leak.

Matt