Hi all,
I'm new to the Forum, and indeed to Land Rovers, and no mechanical genius either. So please go easy on me. I checked through loads of threads here but haven't really found anything that would fit my scenario.

The problem I have is the rear drum brakes on my Ninety. I'm down here in Uganda, with spares and knowledgeable mechanics hard to come by, and Landies that are patched together from ten different models, which makes things rather difficult.
My 90 is (in theory, at least) a 1989 build (VIN FAxxxxxx) that keeps jamming the rear drum breaks, and everybody is at a loss as to why. There is a theory that it may have to do with wheel cylinders that are slightly too large. I have been googling my eyes out but can't seem to find any real evidence of a change in wheel cylinder size, even though spares sites differentiate between cylinders up to VIN VIN HA701009 and after, indicating that there was a change in design somewhere in 1991.
Trouble is that the pictures look pretty identical to me, and there are no dimensions/specifications given on any site.

I also can't be sure if my Landy indeed uses original-sized cylinders and drums from 1989, or has been retrofitted with some later Defender stuff.
Other details:
No original replacement shoes could be found anywhere in Kampala, so lining was bonded on to old worn shoes. Doesn't seem to be too high though.
Smaller wheel cylinders (if they exist) couldn't be found either, so mechanic shaved off 2 mm of the top bit of the shoe, where it slots into the cylinder. No jamming now when cold, but after 6 miles it all heated up, brakes jammed to the point that the engine almost overheated and you could fry eggs on the rims.

So:
1. Does anybody know what the difference, if any, is in size and/or design between pre-HA701009 wheel cylinders and post?
2. Does anybody know which is the drum diameter of Series and Defender models? Since my Landy is sitting with the mechanic and I stupidly forgot to check I can't be sure, but I think my drum diameter is 10.3 inches. Is that possible? Do later models use the same drum diameter or a larger one (which would go a long way)?
3. Any idea that may spring to mind is greatly appreciated.

Cheers!

chamfer shoe edges and check drums not oval or seized brake cylinders

Make sure the return springs are not broken.

Thanks for this.
The cylinders are new (not sure if genuine though, this is counterfeit heaven here) , and so are the springs (previous owner had fitted something that looked suspiciously like a bed spring!)
fanatic, what do you mean "chamfer shoe edges"? the shoe or the lining? and if the shoe itself, which edges?

BTW, for what it's worth, found the part nos of pre- and post-HA701009 on retroanaconda (thanks to the posters here for the link!)
RTC3168 and 69 up to HA701009, STC 467 and 68 after. Anyone knows the difference between them?

franzl said:

Thanks for this.
The cylinders are new (not sure if genuine though, this is counterfeit heaven here) , and so are the springs (previous owner had fitted something that looked suspiciously like a bed spring!)
fanatic, what do you mean "chamfer shoe edges"? the shoe or the lining? and if the shoe itself, which edges?


BTW, for what it's worth, found the part nos of pre- and post-HA701009 on retroanaconda (thanks to the posters here for the link!)
RTC3168 and 69 up to HA701009, STC 467 and 68 after. Anyone knows the difference between them?

Click to expand...

If the lining has a square edge at either end-file the sharp edge so it is chamfered and so it has a ramp effect upto the full height of lining.
Don't go mad, just the sharp angle off

I had something very similar here in Morocco - where my 110 is a similar 'bitsa' and where we also have to make do with local, reconstituted parts etc.

I'd check your master cylinder first. I had the same thing - brakes were fine at the garage, drive a few kilometres and they locked on. I had to use low range to get back on one occasion...

There's also a nut on the end of the shaft that goes into the master cylinder and the local mechanic's tell me it has some effect on the brakes binding, though I don't think Solihul agrees with that!

Incidentally, mine is now on disc braked axles from my old Disco; Range Rover axles should also fit. I prefer them to the fiddly drums.

mhm., I had replied bit that message obviously got lost in cyberspace.
fanatic:
thanks, but the edges of the lining are already chamfered. Plus the marks on the lining seem to suggest that the edges are not where the shoes lock onto the drum. Checking the roundness of the drum may be good idea though.

uncle fes (in fez?)
cheers for that too. i think I'd rather have all discs too.
the master cylinder is fairly new and should be working alright, in the mechanic's opinion, with the exception that the bolts that connect the mc to the servo were buggered by the wrong nuts that were fitted previously. they still seem to hold though so that is probably not the problem. but then, what do I know.
what is the purported effect of that mc nut you mention on the brakes?

fanatic said:

If the lining has a square edge at either end-file the sharp edge so it is chamfered and so it has a ramp effect upto the full height of lining.
Don't go mad, just the sharp angle off

Click to expand...

Try not to inhale the asbestos whilst you're at it though!

I had one new, faulty master cylinder that didn't solve the problem; the second one did... and I bet master cylinders here come from the same place they do in Uganda.

I also changed all the flexi hoses (they can collapse internally) and rebuilt the front calipers - but it was the master cylinder that was the culprit.

Uncle Fez (from Fes)

Alright then, thanks to all for your replies.
So for a while I had thought that the problem was fixed by replacing the current (new, probably crappy Asian aftermarket) with another (old, genuine) master cylinder. But no such luck.
First time I was driving out of town, problems reappeared after 30 miles or so. Not as bad as before, but the rear brakes seized up again, although slightly. A few minutes's rest would free them up again.
However, the problem is not always there. What is always there though is a difference in the "hardness" of the brake pedal. Sometimes, generally with the car warming up after a few miles, the pedal would be very hard and respond very quickly, i.e. you'd barely touch it for it to break. Then, generally when the car is cold but sometimes also in the middle of driving, the pedal would "ease up" and you'd have to push it almost to the floor before breaking begins. In both cases however breaking itself is fine. The few times the brakes seized up was when the pedal was extremely hard.
This tightening-losing up can occur multiple times even if only driving for a few miles around town, but seems to be more pronounced when freely driving overland and the brakes would not be used for a while.
This something to do with the pressure? Any ideas would be greatly appreciated, this is driving me mad. And the local mechanics seem to be at a loss too.
Cheers!

Those are exactly the symptons I had.

It has to be either calipers, hoses or master cylinder - I don't think there is anything else that can give that sensation, unless something has jammed/dropped off inside a drum?

There's a 'pressure limiting' valve to the rear on some models - that might be worth checking.

check when brakes seize fluid pressure by slackening bleed nipple to determine shoe grabbln by fault in drum or fault with fluid not returning and brakes ratchetting on, its more common with defender clutches were rod can be over adjusted and fluid cant return to reservoir quick enough,obviously shoes will be effected by not enough clearance,springs pulling shoes out of line springs not pulling shoes off drum