XJ Mods VSB 14

[alexbrown64]

Originally Posted by alexbrown64

One thing i wasn't impressed with was that they sent a uni that had been previously opened. The uni didn't have the wax paper wrapping and had surface rust. The packet of clips had been opened and one was missing, so i had to use one of the old ones. I wish they would check this stuff before sending them over to the other side of the planet.

Cheers,

I sent a complaint to Rockauto, and this morning my Paypal account had been reimbursed for the uni in full. Hows that for service.

I have to make a bracket to hold the fuel filter on, as its held up with a cable tie, and then just generally go over the XJ in preparation for pit inspection. Still waiting on the engineering report to come through, which i think takes a few weeks.
My Summit racing order is delayed. The order includes a new tranny mount, rims, double cardan uni's and an assortment of goodies.

Cheers,

[alexbrown64]

Well, not sure why but i am suffering from a low brake pedal. Not sure if its because the new front brake pad are 200 kilometers old and are bedding in, or something happened when i replaced the unit bearings. But for whatever reason, the brake pedal seems to be going nearly to floor.
I have created a thread on it to try get some tech responses.
Here....http://www.ausjeepoffroad.com/forum/...d.php?t=145172

Cheers,

[alexbrown64]

The saga continues..

I have always had poor brakes, but a set of new EBC yellowstuff pads did wonders. But now the Jeep has been suffering from a low brake pedal and the brakes just dont feel right.
I clamped the front brake hoses and the pedal felt great again, so the problem is probably in the calipers. I have ordered some new calipers.
I checked the rears out, and there is no hydraulic pressure to the cylinders. They bleed perfectly, cylinders are new, no leaks, and i can do a hand brake skid, so mechanically the rear brakes are OK, but there is just no clamping force using the hydraulics. We jacked the back end up and even at idle in gear and with foot hard on brake pedal, the wheels would still turn.
I did the ZJ proportioning mod trick and it helped. The wheels would actually clamp but still not really hard. No wonder my fronts have had such a hard life.

I did a road test with front brake lines clamped. Something was stopping the car from braking.... the ABS! I unplugged a few relays to disable the ABS, got her up to speed and locked the rear end up.. big skid!! Rear brakes worked great. Reconnected the ABS and no rear end again. Conclusion..... proportioning valve helped get some fluid to the rear end and make them stronger, but the ABS has gone buggy and is interfering in normal braking operations.

A little more research has found that the ABS HCU has solenoid valves that open and close to release/increase pressure to the wheels. Under normal braking, these valves do not operate. Under wheel slip, the valves operate. However, over years of not being used, some of the solenoid valves can become sticky. If you have a sticky valve, the brake fluid can be diverted away from the rear brakes and back through the accumulators and then back to the MC. So, no matter how hard you squeeze your pedal, your brakes wont get any clamping force, even when the ABS is no in use. My rears share one valve/accumulator combo, hence both rears will be inoperable. The fronts have one each. So, others may find their vehicle pulls to one side, if a left or right valve is sticky. This may not show up as a code or light on the dash.

I grabbed a replacement ABS HCU on Ebay for only $20, and an ECU for $30 and they both look to be in good condition. So next will be a bit of trial and error and plug and play to restore correct operation to the system.

So, a good way to test your own rear brakes is to clamp off the front brake lines just before the front wheel calipers and go for a drive.. your backs should be strong enough to lock up... Supercrap has 2 x brake line clamps (like mini G clamps) for $15...

Cheers,

[alexbrown64]

Still waiting on a replacement ABS HCU from the other side of Perth.
The 6 round things are the inlet and outlet solenoid valves. To the left of the unit is the accumulators. These had a lot of gunk in them. I put a 12V source on each one and i can hear them activating. I either have one that is blocked inside, or there is a blockage somewhere else. There is a lot of old solidified gunky brake fluid around. The brown ribbon also carries the 12V signal. This gets old and brittle, and in fact i broke it while pulling a solenoid valve out. I checked the resistance on the solenoids and they all seemed to be in spec. I think they are supposed to be about 3 Ohms and 6 Ohms depending if its an inlet or outlet valve. I could not see how to pull the solenoid apart. I have seen how you can replace the ribbon with soldered wires. The replacement unit only cost me $20 so i just hope it works better than this one. Definitely will be pumping through fresh brake fluid every few months for a while to flush it all out.



Cheers,

[BLAKLISTED]

Great detective work there Alex!

Did all xj's imported to oz have abs? Curious as mine doesn't. It's a 97 classic pre update. Was it optional do you/anyone know?

[alexbrown64]

Pretty sure they were standard on all the Limited's. The rest were an option. Just be glad you don't have it, as its a pain.

Cheers,

[alexbrown64]

I just replaced the HUC with another unit. I checked the operation of all the valves on the new unit, gave it a clean out etc... bled the brakes 3 times including the HCU.
Still no good. If i clamp the front brake hoses and drive with the ABS disconnected, i can lock the back wheels up. If i connect the ABS and drive, it will not stop and no rear brakes at all?
I have just about had enough. Another computer is on the way, and i have taken my old HCU apart, cleaned out the solenoid valves and can rewire them.
I still have the problem of a low front pedal when i remove the clamps from the front hoses. At the moment, the brakes are almost useless again.
I have ordered new calipers and pads, and will install these, together with the new computer and just keep swapping and trialing parts.
Something is not quite right.
Can't think of anything else it can be except the replacement unit is not working right (checks out OK). Don't think it can be proportioning valve, MC or booster as if i clamp the front brakes, the pedal is rock hard, does not drop at all and i can lock the rears up.
Any more suggestions?

Cheers,