M reg. Astra - rear wheels locking.

[Phil7]

I'm scared for my son driving his Astra since he described the car as tending to "fishtail" when braking fairly hard. Sounded to me that the rear wheels had locked before the front and he's liable to be in a high speed spin one day!

He told garage about it, but they passed it for MoT.

Weeks later we could not move the car because the LH rear wheel was locked solid. Jacked it up, couldn't get wheel off, checked h'brake cable. Finally without doing anything in particular it suddenly freed itself!!!

Any experience / ideas much appreciated.

[Phil7]

Thanks for that, mdoo. I'll get it checked out asap.

[woodchopper]

Corsa's and Astras are very similar - I''ve had 4 Corsas - and every one of them at one time or another had your problem - the rear wheel locking is caused by the handbrake sticking on and its usuallly the left one as you say, and if badly adjusted they have a tendency to lock the rear whells as well.
Have a mechanic strip the rear brakes completely and pull the handbrake cables out as well. I'm not sure if the Astra's cable run through a guide on the rear axle but if they do as on the corsas they have a tendency to gather a load of muck and dirt around the cable restricting its movement. When putting the cable back in its guide pack it with copper grease, and when refitting the brake shoes lubricate the contact points where the edge of the brake shoe rubs against the backplate.
Also get them to check the load sensing valve near the back axle and make sure it hasn't seized.

[Phil7]

Thanks a lot, woodchopper, sounds good.

Also, I was wondering what sort of hydraulic pressure limiter there might be.

[woodchopper]

Hydraulic pressure limiter ? - I would assume you mean the load sensing valve - on the corsa's i've had the load sensor is a spring attached to the rear axle if i rmember correctly which attaches to an assembly which actuates a piston - the heavier the load the more brake fluid to the rear brakes and less of a load = less braking done by the rear wheels.
Regardless of what you do, get them stripped and cleaned.

[homer75]

I think the problem you had with the rear wheel locking up and then freeing itself is related to a handbrake cable linkage problem but the 'fishtailing' under heavy braking is probably a fault on one or both of the pressure regulating valves ( fitted on non ABS systems ) on the rear brake lines. They are normally on the rear line outlet ports on the brake master cylinder. Unfortunately these valves cannot be tested without specialist equipment. What is happening is simply that one ( or both ) rear wheels are locking up under heavy braking and this is potentially an accident waiting to happen. Best to get it sorted asap.

[Phil7]

Thanks guys, re load sensor / pressure rergulator, that's what I meant when saying I was afraid he'd have a high-speed spin one day. I've put things in hand and we'll see.

Thanks again, all.