Vehicle pulses when braking - NOT warped disks.

[GHendo]

Thought I’d throw this out there to get some opinions.

For a while now I’ve noticed when I slow down for an intersection etc. – throw the gear lever into neutral as I glide to a stop and apply the brake. I get this, what can best be described as ‘pulsing’ or ‘surging’ feeling in the car – a little bit like having warped brake disks but different – AND the brake pedal doesn’t go in and out.

The brake disks and pads are relatively new as are all the wheel bearings – most of the CV’s have been repacked with grease in the late couple of years when I’ve renewed the boots and they don’t appear to have excess wear.

I normally drive everywhere off road with the short stick in 4H but yesterday, just for the hell of it, I decided to leave it in 2H. And, low and behold, the pulsing appears to have disappeared – I’m going to keep experimenting to make sure I’m right.

My question is, if this is the case, why would the vehicle start this ‘pulsing’ while braking when driven in 4H? I’ve had it in 4H off road for years and never had this happen until a few months ago. Any ideas ?

Cheers
Geoff

[old Jack]

Hi Geoff,


I have had pulsing brakes but the discs were not warped when checked.
It turned out to be brake pad material deposited on the discs in a few places so as you applied the brakes gently the friction between the pads and the disc was not consistent and this resulted in a pulsing feeling under gentle brakes.

https://www.dba.com.au/main/tech-article-to31-friction-material-deposits/

I upgraded my discs rather than getting the factory discs skimmed but I have heard of people being able to remove the deposits on the discs by multiple very hard and extended applications of the brakes.


OJ.

[GHendo]

Thanks OJ … that certainly warrants investigation and I think you might have hit the nail on the head. I have slotted discs and Bendix pads – can’t remember if they’re heavy duty. I probably didn’t bed them in properly when I installed them too, so it looks like that may certainly be the answer.

Cheers
Geoff

[old Jack]

Thanks OJ … that certainly warrants investigation and I think you might have hit the nail on the head. I have slotted discs and Bendix pads – can’t remember if they’re heavy duty. I probably didn’t bed them in properly when I installed them too, so it looks like that may certainly be the answer.

Cheers
Geoff

Hi Geoff,
If you have Bendix pads with the blue titanium stripe then here (apparently) do not need bedding in. On 4wds with 4 disc brakes in most driving you only need yo be gentle on the brakes unless you are heavily loaded, towing or drive in hilly terrain. Just like an engine that benifets from a good long run, I think the brakes need a good hard use occasionally to stop pad material deposits.

OJ.

[Having Fun]

What brings that theory undone unfortunately, is that in the OP, it says that the pulsing doesn't happen in 4H.


I'm thinking (guessing) that the pulsing is ABS related. Happy to be corrected though!

[old Jack]

What brings that theory undone unfortunately, is that in the OP, it says that the pulsing doesn't happen in 4H.


I'm thinking (guessing) that the pulsing is ABS related. Happy to be corrected though!

OP is stating pulsing is only happening in 4H and not detectable in 2H.
Front brakes seem to be more susceptible to pad material deposit and maybe this can only be sensed when in 4H?

OJ.

[Tripplec84]

I have the same issue. Well, not sure if it is an issue. I fitted new rotors and pads all around 33000km ago, but it wasn’t long after fitting them that I experienced the same surging. It’s very slight and only really noticeable when I slow down at low speed and with just slight brake braking.

When I did the brakes I also did new seal kits in all the caliper cylinders so I’ve never been too bothered by the surging because I know everything should be ok, excepts maybe the HBB.

Today I changed from 4H to 2H and the surging seems to disappear as well. Strange one.

By the way mine is a NM 3.5 auto and I currently have DBA slotted rotors with Bendix 4WD pads.

Very interesting read though about bedding in the new brakes. Wish I had known that 33000km ago.

[GHendo]

I have the same issue. Well, not sure if it is an issue. I fitted new rotors and pads all around 33000km ago, but it wasn’t long after fitting them that I experienced the same surging. It’s very slight and only really noticeable when I slow down at low speed and with just slight brake braking.

When I did the brakes I also did new seal kits in all the caliper cylinders so I’ve never been too bothered by the surging because I know everything should be ok, excepts maybe the HBB.

Today I changed from 4H to 2H and the surging seems to disappear as well. Strange one.

By the way mine is a NM 3.5 auto and I currently have DBA slotted rotors with Bendix 4WD pads.

Very interesting read though about bedding in the new brakes. Wish I had known that 33000km ago.

That is really interesting – we have a lot in common. I installed DBA slotted rotors and Bendix pads (pretty sure they were 4WD ones) AND I rebuilt the callipers at the same time. The pulsing is slight and only noticeable when slowing down at low speed. I've done around 60,000km. since I installed them however.

When I get around to it I’m going to pull the rotors off and get them machined – the local guy tells me he can take a minimal amount off them. If that doesn’t fix the problem I will at least be able to dismiss that theory.

Cheers
Geoff

[Lance]

Is DBA able to shed any light on this issue ?

[Tripplec84]

That is really interesting – we have a lot in common. I installed DBA slotted rotors and Bendix pads (pretty sure they were 4WD ones) AND I rebuilt the callipers at the same time. The pulsing is slight and only noticeable when slowing down at low speed. I've done around 60,000km. since I installed them however.

When I get around to it I’m going to pull the rotors off and get them machined – the local guy tells me he can take a minimal amount off thpadsem. If that doesn’t fix the problem I will at least be able to dismiss that theory.

Cheers
Geoff

Sounds like a plan Geoff, I might need to do the same when I do pads again.

I wonder if anyone else has this problem and if they also have DBA rotors and Bendix pads , maybe the fault lies with the product?

I’ve never head anything bad about the 2 and they are quite reputable which is why I decided on them.

My wife drives a VW Polo and I recently fitted new DBA slotted rotors and Bendix pads to her car. I will take note of the way it brakes next time I drive it, her car has however only done about 2000km since I changed them. Will be interesting if it does the same thing though.

Cheers
Charlie

[Marz]

Was going to post a long winded logical possible explanation, but thought better of it, LOL...


Check the front prop shaft, i.e. universals (greased them lately? last time you replaced them?), possible that the prop shaft could be ever so slightly bent or lost a balance weight.


I don't think it's a disc/hub/etc problem. You change the way the drive train runs (by selecting 2H or 4H) and the problem comes and goes..... Check the drive train.

[spot01]

I wonder if it is something to do with the tyres that is more noticable in 4H?
Are they getting on a bit?
Older tyres sometimes get a bit "out of round" - might be worth swapping them front to back to see if anything changes?
I'm also a fan of giving the brakes a few hard stops from higher speed to clean them off.

[GHendo]

Was going to post a long winded logical possible explanation, but thought better of it, LOL...


Check the front prop shaft, i.e. universals (greased them lately? last time you replaced them?), possible that the prop shaft could be ever so slightly bent or lost a balance weight.


I don't think it's a disc/hub/etc problem. You change the way the drive train runs (by selecting 2H or 4H) and the problem comes and goes..... Check the drive train.

Hi Marz

Yeah, the drive train was something I had been thinking about from the beginning. There is only one grease nipple on the whole vehicle, and that is on a universal on the drive shaft that comes out of the front diff – and ‘yes’, I do grease it.

All the front CV’s etc. are original and have done about 330,000km. I thought they were ok but got a mechanic to check them as well – he confirmed they were fine. I have repacked them with grease when replacing boots at least once, each.

On a trip to Brisbane last week I switched between 2H and 4H and while the pulsing was not quite as bad in 2H, it was still noticeable. My son, who I picked up in Brisbane, noticed the pulsing right away even though I hadn’t mentioned it so maybe I’m getting used to it !

Cheers
Geoff

[GHendo]

I wonder if it is something to do with the tyres that is more noticable in 4H?
Are they getting on a bit?
Older tyres sometimes get a bit "out of round" - might be worth swapping them front to back to see if anything changes?
I'm also a fan of giving the brakes a few hard stops from higher speed to clean them off.

Hi Spot

I’m running Copper ST/Maxx and they are pretty new – only done about 12,000km. and are due to be rotated, but I have my doubts if that is the cause of my problem.

When I get a chance I’ll take the rotors off and get them machined to see if it makes any difference. That will be my starting point. If I still have the problem I’ll probably then look at the drive train.

Cheers
Geoff

[old Jack]

Hi Spot

I’m running Copper ST/Maxx and they are pretty new – only done about 12,000km. and are due to be rotated, but I have my doubts if that is the cause of my problem.

When I get a chance I’ll take the rotors off and get them machined to see if it makes any difference. That will be my starting point. If I still have the problem I’ll probably then look at the drive train.

Cheers
Geoff

Hi Geoff,

Have you tried the multiple very hard applications of the brakes yet. Do 5 or 6 full braking stops from 80kph and get the brakes nice and hot, just so you can smell them and then go for an easy drive with to let them cool down. If it is pad material deposit on the rotors this should wear it off.


OJ.