Rav4 Shuddering Over 50mph (sometimes)

February 4, 2008

Hi all,

This is my first post and hopefully someone can help.

I have a RAV4 2.0 GX P-reg. It is in very good condition.

Forgive the pre-amble but it may be useful.

Last Jan I noticed my car slowing down on motorways and the braking became very sensitive. I was informed that the calipers had seized. I changed them and after a few weeks I noticed shuddering through the steering wheel and also vibrations on braking. Last October I changed the calipers for the 2nd time and also the housing, screws and everything on the braking system. I also bought new pads. The old ones were worn at an angle. The mechanic showed me the old calipers and said that one of the arms was bent inwards slightly.

It all seemed to be working well but after a few weeks I travelled on the motorway and above 50mph the shuddering began. After a few mins it stopped and all was OK. This is still continuing. The curious thing is that sometimes it shudders and sometimes not. I can't seem to find a common theme when it shudders or not. I doubt it is the calipers again but a more fundamental thing is behind this. Maybe the disc itself? It does seem to happen after the car has been travelling for 10-15mins, i.e. when things have heated up. It does not happen at all at lower speeds no matter how much I drive. I still however get the instance of the brakes being sensitive still occasionally.

Any ideas people?

Your in anticipation

Mandeep

February 4, 2008

OK - here we go

I have a '94 RAV which had the exact same problem - calipers sticking - especially the drivers side one at the front -

when they stick, they cause excess heat which then warps the disc. The disc on the early RAVs was quite thin...I went through too many sets of discs to want to remember!!

Ye - when the caliper heats up, it can seize - ie the sliding shoe seizes and everytghing heats up and then you get the vibration; shuddering; and driving as if the RAV is nose down + use more petrol.

First thing you need to ensure is that the 2 front discs are not warped or not flat. This would cause shuddering on braking and other funny noises as the disc hits the pads off and on.

You also need to check that the caliper pistons are returning properly; and that the shoe that slides on the 2 bolts is free to slide...+ make sure the bolts are clean and free of built up gunge...which happens.

Did you have new calipers fitted, and were they a complete assembly..?

What mileage has the car done??

I got completely fed up with the calipers trashing discs, so had new ones made up by KAD - essentially a 6 piston caliper set with 3 pistons per side of each disc. Work tremendously, as they should, but wasn't cheap.

I think the original caliper must be prone to corrosion and the design prone to wear after a fair mileage.

I'd try the caliper operation first to check the shoe slides back and forward over the disc and that the piston goes back to release pressure from the disc pad,

Ian

February 5, 2008

It should be possible to jack the vehicle up and spin the wheels to see if they are free. A good starting point is to stop the car on a very gentle (nearly level) slope and see if it rolls.

Don't forget it could be wheel balance or one of many other rotating parts. You need to try and take the brakes out of the equation. If they are binding enough to cause judder they will usually give off a resin smell from the heat and may even show some blueing or discolouration of the discs. Whatever you do - don't touch them. You can spit on them as a quick test!

February 5, 2008

I forgot to say that a simple test is when you stop after a few miles run, feel the wheels to see if they are hot.

February 18, 2008

Thanks for the reply. It seems we both faced the same problems.

I had changed the calipers twice now and the 2nd time was the complete housing. The car has only done 72K miles.

Could it be that warped discs are damaging the calipers?

I have noticed alot of brake dust on the alloys and it does seem to get very hot.

I do notice that on a flat road the car does not always roll as the brakes are applied and it seems that the pads are constantly touching the disc, and when jacked up the wheel does not always turn freely.

Should I buy new discs and is it easy to change?

Thanks

February 18, 2008

Thanks for the reply. It seems we both faced the same problems.
I had changed the calipers twice now and the 2nd time was the complete housing. The car has only done 72K miles.
Could it be that warped discs are damaging the calipers?
I have noticed a lot of brake dust on the alloys and it does seem to get very hot.
I do notice that on a flat road the car does not always roll as the brakes are applied and it seems that the pads are constantly touching the disc, and when jacked up the wheel does not always turn freely.
Should I buy new discs and is it easy to change?
Thanks

You'll get brake dust on the alloys as a matter of course. The wheels should not get hot though...as anchorman said, the car should be able to roll freely on the level or down a slight slope. On jacking up the wheels, they should turn fairly easily when in neutral - they won't spin due to the drag of the 4 wheel drive transmission.

The pads will always touch the disc, but should not grab the disc.

As for the disc being warped, you'd notice it when applying the footbrake as it would give a pulsating feeling. With a front wheel jacked up, you can turn the wheel to full lock to watch the disc turn and measure the disc - caliper distance - it shouldn't 'wobble' or vary. To do this, mind that with the wheel off, the disc will be loose so you could put the wheel nuts back on with washers if need be to secure the disc.

If the disc is unevenly worn, the thickness can be checked with a micrometer. The proper thickness is stamped inside the disc.

On the caliper replacement - was it the caliper and shoe that fits over the disc that you replaced ...and were they new or 2nd hand? And is the disc an original smooth disc or is it grooved (eg for better stopping - see an after market supplier like EBS or Demon tweaks for examples).

Shuddering can also happen if the bushes of the transmission system are worn...for example the central bearing that holds up the rear propshaft. This would be more noticeable with speed. I'll try to think of other things...