LC80 (Dec 92) - 'turning ABS off'?

[AndrewCorser]

I have had continuing trouble with my braking system, and especially the ABS, for the past 15 months (Dec 1992 HDJ80 VX 4.2). I have had most of the hydraulic related components replaced, and have had several parts of the ABS system replaced or serviced, but there is still an occasional engagement of ABS on normal braking around both 30 mph and/or around 15 mph, followed by the ABS light coming on, and the ABS seemingly switching off.

In a manual I have obtained: 'Toyota Repair Manual for Chassis and Body' dated Aug 1992 for (among others) the HDJ80, under the ABS section, there is the following:

BR-34
BRAKE SYSTEM (STATION WAGON) - ANTI-LOCK BRAKE SYSTEM (ABS)
SPEED SENSOR AND DECELERATION
SENSOR DIAGNOSIS SYSTEM
DIAGNOSIS SYSTEM INSPECTION
PRECAUTION
While checking the speed sensor diagnosis system, ABS
does not operate and brake system operates as normal
brake system.

...so does this mean that I can do something that will make the 'ABS ... not operate and [the] brake system operate as [a] normal brake system'? Given the problems which we have not managed to solve over many hours work in the last 15 months, I would prefer it if the ABS didn't operate at all: it would feel much safer, as I would know the brakes were not suddenly going to pull one way or the other, or even not operate at all.

So can I 'switch off' the ABS? And if so, I could justifiably remove the bulb from the ABS warning light (as there would be no ABS to check on) making the brakes acceptable to an MoT test?

 

[Shayne]

I hated the ABS in my 90 series until I sent my calipers to Big Red for a rebuild and replaced all the discs with M-Tec dimpled and grooved , not sure i ever heard the dreaded ABS rattle again .

 

[Towpack]

Have you tried checking for any fault codes stored in the ABS ECU which should give you an indication of where the fault (if any) is?
Reading the diagnostic procedure in the FSM it does appear that ABS operation is disabled during the diagnostic process but not the dash warning light which is used to give indication of correct function.
Assuming all the hydraulics are now working OK, I'd hazard a guess and say it's the deceleration sensor at fault.

Disabled or faulty ABS will fail the MOT even if the dash bulb is removed assuming it's spotted by the guy doing the test. I quick look under the bonnet will be a dead give away.

 

[felix2566]

You mention the brakes pulling all over the place, is this the ABS doing it or do you have a sticking caliper as Shayne possibly had before he got them rebuild.

Unless you already have done so, I would check that the actual sensors are not at fault either

 

[Jon Wildsmith]

For MOT the ABS light needs to come on when the ignition is turned on, and then go out after a while, so no light on a car that the MOT testers computer is telling them has ABS will be a fail.

Random activation of the ABS like you describe, especially at lower speeds, is usually a wheel speed sensor fault. Getting the code from the ABS ECU will give you an idea why it's putting the light on.

 

[Highlander]

Several people have done full ABS delete, and report their cars stop altogether better without it. Where that leaves you in terms of insurance I'm not sure. Also, you need to pay attention to just how much you might need to delete to pass MOT. Do you have to remove the ABS sensors themselves? If so you need new non-abs knuckles, or some way to neatly plug the old ones.

Many ABS problems seem to be to do with air in the ABS mechanical brain that's impossible to bleed normally, and I think this is the most likely cause of the majority of persistent ABS issues with these vehicles. There is a hack to activate the ABS while bleeding that might do the trick, but I haven't done it

I swapped all my callipers for Roughtrax ones and it solved most of my problems, would still like to try this process. I have a pressure bleeder system to help once I get round to it

 

[Lorin]

Removing ABS and/or LSPV is completely legal when done correctly. Both improve braking, markedly so if running larger tyres. See https://www.landcruiserclub.net/community/threads/removing-the-abs.146500/

 

[Highlander]

Removing ABS and/or LSPV is completely legal when done correctly. Both improve braking, markedly so if running larger tyres. See https://www.landcruiserclub.net/community/threads/removing-the-abs.146500/

Did you leave the ABS sensors in the knuckles and just remove the loom?

 

[felix2566]

I have seen companies that make blanking plugs to for the redundant ABS sensor hole. But dont see why you couldn't leave the redundant sensor in the hole

 

[Lorin]

Did you leave the ABS sensors in the knuckles and just remove the loom?

I removed the sensors and used plugs as felix2566 mentioned. Had to order from US but didn’t cost much. To pass MOT all visible trace of ABS must be removed and you need to pull the ABS bulb in the dash

 

[felix2566]

Having just bought a whole load of parts from Delta I can vouch for the quality of their parts, it is very good.

Delta Vehicle Systems - DVS 80 Series ABS Sensor Hole Plugs

Toyota axle ABS sensor hole plugs

www.deltavs.com

 

[chapel gate]

what lorin says. i removed all that over complicated junk years ago. it was lethal in snow and ice. removal of the ABS pump leaves a great space for a compressor.

 

[LandcruisingFarmer]

Crikey, my 80 doesn’t have ABS and I was thinking of fitting it to make it safer. Now I’m think that’s a bad idea!

 

[Towpack]

I don't want to tempt fate here but I've never had any issues with the ABS, even in snow and ice you have to stand on the brake quite decisively to get it to kick on. Maybe tyre selection, size, tread pattern etc plays a big part in it's effectiveness? Perhaps it's optimised to work best with the heavily road biased tyres the vehicles left the factory with.

 

[chapel gate]

I don't want to tempt fate here but I've never had any issues with the ABS, even in snow and ice you have to stand on the brake quite decisively to get it to kick on. Maybe tyre selection, size, tread pattern etc plays a big part in it's effectiveness? Perhaps it's optimised to work best with the heavily road biased tyres the vehicles left the factory with.

Possible TP.
I didn't want to spend time and money on something I didn't like anyway.

 

[Lorin]

I don't want to tempt fate here but I've never had any issues with the ABS, even in snow and ice you have to stand on the brake quite decisively to get it to kick on. Maybe tyre selection, size, tread pattern etc plays a big part in it's effectiveness? Perhaps it's optimised to work best with the heavily road biased tyres the vehicles left the factory with.

I think increased tyre size, suspension lift and rear springs with a heavier load carrying capacity (that negate proper LSPV functioning) are all factors that undermine proper ABS functioning.

 

[Shayne]

I personally don't like abs , which was designed specifically to save airlines money in burning rubber during landing .

But when your brakes are in good condition your never likely to know you have it . The op has invested time and money making sure the abs are in better nick than mine .

Frustration led to the question and i think the answer is that the abs was working fine all along because its job is to prevent wheels locking up and skidding when you slam on . When calipers , or discs or , pads are unequal in effect one wheel will lock up early triggering response .

Should note before overhauling the brakes on my 90 with the hated abs I thought the truck stopped good . I was astonished at the improvement . Caliper rebuild and disc replacement were the first job I did on the next two trucks .

 

[Grimbo]

Can you not just pull the ABS fuse ?
On my 96 plate 80 putting it into low range disengages ABS....
If you can simply pull the fuse then leave like that and just put the fuse in come MOT time ?

 

[AndrewCorser]

Have you tried checking for any fault codes stored in the ABS ECU which should give you an indication of where the fault (if any) is?
Reading the diagnostic procedure in the FSM it does appear that ABS operation is disabled during the diagnostic process but not the dash warning light which is used to give indication of correct function.
Assuming all the hydraulics are now working OK, I'd hazard a guess and say it's the deceleration sensor at fault.

Disabled or faulty ABS will fail the MOT even if the dash bulb is removed assuming it's spotted by the guy doing the test. I quick look under the bonnet will be a dead give away.

Hi Towpack, thanks for your useful reply!

Do you have experience with replacing the deceleration sensor? I Have found one on-line from Japan, but quite expensive, so I would like to be sure it is faulty. I get occasional engagement of the ABS around 30 mph, which is apparently indicative of a faulty deceleration sensor...but this is only occasional, and the much more common engagement is at 10 mph, which I understand implies a wheel sensor problem. We have put a new wheel sensor on the front, and swapped that round with the existing one on the other side, and had the same fault codes in both configurations, and since that type of fault allegedly arises from the signal from a dodgy sensor being most obvious at very slow speeds, that would suggest it is not the wiring loom.

Anyway, thanks again for you help!

 

[AndrewCorser]

You mention the brakes pulling all over the place, is this the ABS doing it or do you have a sticking caliper as Shayne possibly had before he got them rebuild.

Unless you already have done so, I would check that the actual sensors are not at fault either

Thanks!

I have had all the callipers replaced, so it shouldn't be that (unless the disks would affect it? They were in reasonable condition).

On the wheel sensors, I got a replacement front one, and we tried it on both sides, but got the same fault codes, suggesting it isn't the front sensors. We also checked the cleanliness and condition of the toothed sensor rotors on the front. At the back we have only checked one of the sensors...but the symptom is the juddering ABS feeling through the brake pedal at 10 mph, AND pulling (one way and then the other) which suggests to me it is related to the front sensing rather than the rear sensors. I suppose I could replace both front sensors with new ones since I have now found those on-line (the replacement one was from Karl and I'm not sure if it was new).

Thank you everyone for your support on this issue! It is really frustrating: at 71, I want this special 30+ year old vehicle to see me through another 30 years, and the only outstanding issue is this ABS!