Hydroboost brakes

etbadger · 03-12-2010, 02:13 PM

Been doing a bunch of work on our van, and thought some of it may be of interest to folks here. Figured I would start a few threads to discuss the changes.

One of the issues that has been a bit of a bother to us was the foot pressure required to hold our van still offroad when descending steps (especially for all sub-100lbs of Amy). This was exacerbated by our 37" tires.

Then when our engine died last fall and left us without much in the way of vacuum assist on the brakes to stop while descending a hill the brake issue was raised again.

Some reading and research revealed all the nifty expensive new rotors, calipers, pads, etc. Unfortunately money is expensive, and these solutions too quite a bit of it. This also wouldn't address the lack of significant vacuum storage on engine failure, nor the apparently limited lifetime of some vacuum pumps (our van is diesel) that some folks experience.

We decided to go the route of the E450 and pickups, and convert our brake system over to a hydro-boost system (using power-steering fluid to multiply brake-pedal pressure, rather than the huge vacuum drum in the van stock). The units also have a hydraulic pressure reservoir for a few hydraulic assisted brake pushes after the engine dies, at higher assist rates than the vacuum reservoir system allows.

We stuck with the stock master cylinder since it is sized appropriately. A few adapters to match it to the hydroboost unit from an E450, some hydraulic hose and fittings, and a day of tinkering to get everything massaged around in the engine compartment.

After installing everything, including a much larger power-steering fluid cooler, I refilled the lines, purged everything and re-bled the brakes. A pressure gauge on the front calipers coupled with a bathroom scale on the brake pedal shows about 33% more brake pressure for the same foot pressure compared to the stock vacuum booster.

Driving test yields noticeably better braking, without being too sudden. Total cost was about 300$ with all new hydroboost, lines, fittings, and fluid.

This improvement can still have the standard improvements applied as well (rotors, pads, calipers, etc).

There is a bit more detail and background on our website at http://www.badgertrek.com/sportsmobi...e.shtml#Brakes

-e

Ford_6L_E350 · 03-12-2010, 06:06 PM

What year is your van? Mine is an 04 and I believe it came with hydro-boost brakes.

Mike

etbadger · 03-12-2010, 06:46 PM

Our van is an early `05. We were told by someone at SMB, when ordering, that it had hydroboost brakes, but that clearly wasn't the case when we looked in the engine compartment on pickup.

From recent reading I believe vans with dual alternator will have hydroboost (need room for that 2nd alternator where the vacuum pump is). Some 350 vans in prior years (late 90s?) also came with hydroboost stock.

For those that don't know: If you look in the engine compartment toward where the brake pedal comes through the firewall (behind/below coolant de-gas tank in the 6.0L Diesel) and see a giant black drum then you have vacuum boost, if you see a gadget like in my photos above, with 3 hydraulic lines, then you have hydroboost.

-e

carringb · 03-13-2010, 11:59 PM

Well I ordered mine hydro-boost master cylinder today. Been on my list for a while, but you inspired me. Biggest complaint for me is that when pulling steep grades with cruise control on, I'd loose boost so power brakes would be non-existent initially.

BTW - it looks like you ended up with the pickup version. The van version has the 3 hydraulic lines coming off the top vie a mounting bracket.

Also, the vans normally use a return tee below the reservoir. The hydro-boost reservoir is the same part, at least for 2000 era vans.

etbadger · 03-14-2010, 10:11 AM

What we picked up is an 05-07 E450 hydroboost unit (PN: 6C2Z2005AB). The master cylinder is the 05 E350 vacuum boost master, but I machined some adapters (the couple inches of AL you can see between the two). The lines we used are all custom-built, I did not pick up the bracketry or lines from Ford, but chose to make my own from SS braided hydraulic line. By using the E350 master there was a bit of interference from the cruise-control backup cutout switch and the ABS module (the hydroboost masters have that switch clocked about 45deg), so I moved the ABS module an inch rearward.

The pickup hydrobooster is very similar, but the pedal pushrod is too long by a couple inches, and not easily removed for changing (not adjustable like on some older vehicles with a clevis & some nuts). I do not know if the pressure ratio (internal guts) is the same for the pickup and van boosters, the information on them is sparse. The castings are slightly different, so there may be different sizes of boost pistons internally, or perhaps just different manufacturing runs between the boosters I got my hands on.

-e

carringb · 03-14-2010, 12:18 PM

Ah... It must be the build year that makes it look different. Luckily for my year van, all the brakes lines and the power steering system are pretty much the same... Just some different hoses.

The E450 master cylinder does have a larger bore compared to the E350 (at least in 2003 and older). But I'm not to concerned since I suspect it makes more effective boost, and I will also be going to the '08+ front calipers, which also have larger pistons.

PS - Here's all the specs on your van, including master cylinder sizing:
https://www.fleet.ford.com/truckbbas...eriesvanbb.pdf

etbadger · 03-16-2010, 10:19 AM

Thanks for the link to those spec sheets. I had not seen that before.

The van and truck hydroboost units are the same in terms of power-piston diameter.

The numbers also let me do a bit of crunching for maximum boost to the brakes:

Theoretical hydroboost brake boost maximum:

Hydroboost area: (1.56/2)^2 * 3.14 = 1.91 sqin
PS Pump assume 1400psi
= 2674 lbs on master cylinder pushrod
2674 psi / 1 sqin = 2674 psi in the brake lines (1 1/8" master cylinder)

Vacuum brake boost maximum:

Boost area: (13.46/2)^2 * 3.14 = 142 sqin
Boost pressure (best possible @ sea-level with perfect vacuum pump) = 14psi
= 1988 lbs on master cylinder pushrod
1988 psi / 1 sqin = 1988 psi in the brake lines

2674/1988 = 1.34

So 34% increase, which is just about the ratio I measured at lower pedal pressures (they are not necessarily related, but this shows its a rather linear improvement). Of additional benefit is that hydroboost will not diminish with altitude, and I can get a somewhat higher pressure aftermarket power-steering pump to get greater boost (I believe some hydroboosts have a set high-pressure blow-off of around 1600psi on the hydraulic line, unsure of ours). Additionally foot pressure multiplied by the lever ratio of the brake pedal is added to the numbers above, so max brake-line pressure is probably about 4-500 psi higher when really stomping on the pedal, though this addition is identical for either type of booster.

-e

carringb · 03-16-2010, 06:15 PM

Thanks for doing the math. It's finals week for me so my head already hurt.

I pick up the new '09 front axle from QuadVan tomorrow. The new axle has brake pistons 2.36" vs 2.2" on the pre'-08 models. Also, the new rotors are 13.58" vs 12.90". And, the caliper itself is larger so I expect less deflection under high brake pressure. Overall, I expect a pretty good improvement.

saline · 03-16-2010, 06:24 PM

Quote:

Originally Posted by etbadger

Thanks for the link to those spec sheets. I had not seen that before.

The van and truck hydroboost units are the same in terms of power-piston diameter.

The numbers also let me do a bit of crunching for maximum boost to the brakes:

Theoretical hydroboost brake boost maximum:

Hydroboost area: (1.56/2)^2 * 3.14 = 1.91 sqin
PS Pump assume 1400psi
= 2674 lbs on master cylinder pushrod
2674 psi / 1 sqin = 2674 psi in the brake lines (1 1/8" master cylinder)

Vacuum brake boost maximum:

Boost area: (13.46/2)^2 * 3.14 = 142 sqin
Boost pressure (best possible @ sea-level with perfect vacuum pump) = 14psi
= 1988 lbs on master cylinder pushrod
1988 psi / 1 sqin = 1988 psi in the brake lines

2674/1988 = 1.34

So 34% increase, which is just about the ratio I measured at lower pedal pressures (they are not necessarily related, but this shows its a rather linear improvement). Of additional benefit is that hydroboost will not diminish with altitude, and I can get a somewhat higher pressure aftermarket power-steering pump to get greater boost (I believe some hydroboosts have a set high-pressure blow-off of around 1600psi on the hydraulic line, unsure of ours). Additionally foot pressure multiplied by the lever ratio of the brake pedal is added to the numbers above, so max brake-line pressure is probably about 4-500 psi higher when really stomping on the pedal, though this addition is identical for either type of booster.

-e

I have a question.....What? Seriously though I think I learned a bit about brake systems from the above posts.

etbadger · 03-18-2010, 06:30 PM

Quote:

Originally Posted by saline

I have a question.....What? Seriously though I think I learned a bit about brake systems from the above posts.

Basically these are just computations to figure out how much maximum power assist to the brakes that the two systems can give. I had measured a 33% improvement in brake application pressure for a given foot pressure on the pedal, but this didn't say how far the benefit extended.

The computations showed that the maximum power assist of the hydroboost was also about 33% greater than the assist proved by the stock vacuum brake booster. This would be equivalent to fitting rotors about 4 inches larger all around (not accounting for heat capacity, but I don't race the van, I just want good holding power with the occasional stop).

-Erik