Vibration when brake stepped on at standstill, 2009 GU

[Hodge]

Got a funny one for you folks.
This has happened to me several times, but today was just another episode, so thought I'd ask.
After a drive at high speed (in my case the ring road @ 100km/h) and then after slowing down to stand still (red lights / off-ramp). Every time I step on and off the brake, there is a vibration present. Cannot pin-point where it's coming from it's really unusual and very distinct, definitely not normal. It disappears after a short drive at lower speeds and/or if I'm standing there still for a while.
The 2 common denominators that I can think of every time it's happened are air con was on and day was warmish. I thought maybe the compressor each time it kicks in, but, only happens after a drive at speed as I mentioned above, it doesn't happen any other time.
Other than that the car is functional I don't lose any power or anything like that. Everything works as per usual.
My obvious suspect is air con. But I don't even know where to begin looking, and WHY it happens with the foot on the brake?
Any suggestions will be appreciated!

[92GQ]

Vaccum leak maybe?

[Ben-e-boy]

X2 vacuum leak, I am pretty sure that if you are stopped and at idle and you put your foot on the brake and the rpm drops there is a vacuum leak.
Long shot but try that

[Hodge]

Thanks boys! My mate instantly suggested that as well. But on contrary, if it were a leak, wouldn't it happen all the time, instead of after coming down from a drive at higher speeds ? On normal conditions, I've never seen my revs drop at idle, if brake is stepped on. But there is a starting point!

[Ben-e-boy]

If you had no vacuum the breaks and clutch would be hard as fork. If the leak is slower than the pump can create vacuum it would still be able to keep up but work harder

[Hodge]

Cheers for that mate. Will get it looked at.

[threedogs]

Are they ABS brakes ?????

[Hodge]

Are they ABS brakes ?????

I believe so yes. It's got the bosch thing under the hood.

[threedogs]

That's your vibration or pulsing that's how they work

[Hodge]

That's your vibration or pulsing that's how they work

So the abs system may be knackered ?

[taslucas]

That's your vibration or pulsing that's how they work

At stand still though?

[threedogs]

ABS could be playing up,


EDIT: How is the pad wearing is it even or tapered to one end.
Heard ABS can be a PITB

[Robo]

ABS only pulse's when you lock up a wheel.
Not while the vehicle is stationary, abs should not be working at all then.
If it does you have abs issues.

The abs pulse you feel is abs unlocking / bypassing pressure to the brake that has locked for a part second.
Once the wheel is turning again it closes the by pass again and you have brake back at the wheel that was locked.
The pulsing, as felt under your brake pedal foot is a succession of abs cycles, unlocking and locking.

Think you are on track for a vacum leak somewhere as you thought.
Iv'e felt mine do similar as you describe,and it does not have abs.
only difference I don't recall speed playing a part.
that is I simply don't remember noticing problem after speed.
only a slight hick-up in reves and vacum, as I have spotted on the a vac gauge I installed .

one day I will catch up on chores and get to the bottom of it.

cheers

[Col.T]

G'day Hodgie,
Tassie's point is valid and Robo's explained it well. ABS in my case has only been felt through the right foot in a sudden, dark brown underwear, panic situation, never at a slow down at the lights.
Clutch (if power assisted) and break systems should be seperate and therefore easily picked as the problem. Mind you, I've not checked the manual so I've possibly stuffed up again.
A/C is a big drain and you can feel it come on and see the revs. drop but I don't ever recall it 'pulsing'. After a speed run, stopping reduces air flow over the radiator and may increase engine temp. but that shouldn't effect the A/C..
Maybe crack a coldie, (I've got some top home brew recipes if you need help), and wait for Robo to came up with the goods.
In the meantime though, might be interesting to get the Missus or someone to cruise down an open country road , pull up to the usual type stop, get it pulsing, keep the foot/feet on the appropriate pedal while you leap out and get under the bonnet/wheel arch etc. etc. and see if you can locate the little swine.
Isn't life fun?
Regards,Col

[Col.T]

Strewth!!!
'break',,,,,'seperate',,,,,
Aint home brew good
Col

[Hodge]

Thanks a lot for all your input folks.
I attempted to replicate this phenomenon today without any luck. Although I was only doing 80 on the ring road for a while, nothing above.
I should describe this vibration a bit more. Few of you mentioned pulsing. It isn't pulsing as such, and I cannot feel it through the pedal (brake) and my foot at all. It's more of a vibration somewhere up front I believe. Kind of like something is loose and is rattling on top of the engine, but it feels heavy? If that sort of describes it. Kind of like a larger compressor running on a lower frequency.

[Robo]

Humm,
maybe try checking any idler pulleys for wear n tear.
these can chatter if dry and or worn out.
power steer pump possibly !.

some one recently wrote in a thread about aircon causing trouble.
it was locking motor up I think.

http://www.nissanpatrol.com.au/forums/showthread.php?23305-Patrol-wont-start-nissan-say-its-the-air-con-pump

good luck keep us posted

[Robo]

The brake master vacum booster may have a leak or faulty check valve .

[Hodge]

Bumping this back up to the top. Had a mechanic look for a vaccum leak and he's found nothing.

I'm now quiet certain, that it actually has nothing to do with the brakes. Today, as well as a few times recently this "vibration" kicked in when stopped, after a lengthy drive after a bit of power was needed. Was around kangaroo grounds today and a few hilly sections I pushed the car a bit and after a while, when I've come to a stop sitting at the lights, this vibration kicks in!
It's very hard to explain... It's like something is rattling all of a sudden somewhere under the hood and is felt inside the car. Opening the window to try and listen to it from the outside reveals nothing. Next set of lights, it goes away, like nothing ever happened.
A slight tap on the gas pedal makes it go away. SO it's happening during idle after a bit of a drive when pushing the engine.
Once again, I do not lose any power, nor does the car feel any different.
I'm stumped as to what it could be.

[Col.T]

G'day again Hodgie,
been off screen a few days and nice to see you're still enoying life.
The absolute duck's guts, spotty the dog, SOB problem is the 'intermittent' one and looks like you've got a beauty.
Still think your only hope is the long drive off road so you can push it, stop as often as it takes without passing traffic danger and then when it starts, get out and go searching. Touch nothing as long as it continues, well not the throttle from what you say and if need be, get a longish screwdriver and use it as a stethoscope under, over and in the guts to find the source.
Nothing you've described so far gives me any idea where to start (not that that's surprising) so for mine you're still at the make it start and then find it stage.
'All the best,
Col

[threedogs]

Do you have a fan fitted to your intercooler or an aftermarket trans cooler if an auto ??
Do you have the vacuum pump on end of alternator, mine made small noise at idle and disappeared on take off
Never lasted as long as your noise though, next I can only think the belt pulley tensioner is on its way out and letting off warning signs
just throwing all this out there at random

[happygu]

Hodge,

Have you followed up from the possible dodgy engine mounts thread?

Could they be the cause?

Mic

[Hodge]

Hey folks.
I haven't followed up on any of the stuff as I'm very short on time at the moment, and with this union vs. company s*** happening at work, I'm unsure where I stand financially or with my job for that matter so I'm a little hesitant to start booking it in, getting things looked at and/or replaced. Anyways thats another story...
@ threedogs - No intercooler fan, but speaking of fans, for a moment I though it may be the main engine fan doing "something" while engine gets hot after a bit of a power drive

@happygtu - I had a good look at the mounts my self today with a mate, and there doesn't appear to be any wear or anything, engine doesn't move much under the hood, and the stick has a tiny bit of left/right movement, but more so back and front...

@col.t - Yes! They are the worst of all problems, the ones that come and go, and this one is... well, doing my head in. Engine runs fine, idles smoothly, I have all the power there, nothing sounds out of the ordinary.

[Hodge]

OK bringing this up to top again as today I've experienced this a number of times.
I am beginning to suspect it could be the fan up the front.
I'm not 100% sure how exactly this fan assembly works. So there is a clutch in it (thermal). Once it reaches a certain temperature, it engages and in turn the fan kicks in, is that how it works ???

[Col.T]

Hodgie,
g'day again,
from what I can see, the fan has no wiring so is presumably not thermostat/electrically driven,,,,,presume!!
Therefore it is / should be a clutch operated unit (maybe), which is driven by the water pump which in turn will/may/could be driven by a thermostat .
I'd rather hope that if that is the prob. it should be in a rather loose state and a good tug on the blades would show any free movement in the unit/bearings. Don't be too aggressive though as the plastic gets brittle with age and heat.
This is possibly all rubbish but it's all I've got,
good luck
Col

[threedogs]

its driven when the fluid inside gets to a certain temp it will lock and drive the fan. I know you can replace fluid using a
bottle of Tojo therm fan fluid, but not sure on Patrol, not the cheapest tool in the shed BTW

[Col.T]

G'day Doggy,
does that mean you need to remove the fan/clutch assembly and drain/replace the fluid?
Don't want to appear even dopier than usual but I don't know how that works. That may well be because I've never had that problem. Can you go a bit further?
thanks,
Col

[Maughany]

G'day Hodge,

i know this is a bit of a thread dig and also being my first post on this forum but im trying to do a little research as im also experiencing this problem in my 08 gu st 3L auto,
i have found with mine it is very intermittent but also unlike yours speed or distance travelled seems to have no consistency it can happen immediatly at the end of the street or after a half hour drive a 110km speeds. all i can see is that on my scan gauge on braking at the decrease around 15-30km the revs will drop form the idle 750rpm to around 695-715rpm for a short period of time until i have either come to a complete stop or hit the accelerator again.

ive gone through the same symptoms you list and also expected the same problems whether it be a seizing idler pulley, tight aircon compressor, or even the stall converter in the transmission giving me grief but still havent quite been able to nutt out the problem.

If you have manage to find this or have the problem fixed i would love some feedback.

Cheers for any help or information.
Rob

[Hodge]

G'day mate. Yes I have diagnosed my vibration, although It's more of a rattle than vibration.
My one ended up being a loose exhaust system somewhere along the line. I still haven't pin pointed where. So basically when the system sees some high EGT's for a while and exhaust heats up (long run @ 100km/h), then when I stop it begins rumbling until it cools down a bit.
The reason, I originally assumed it was a vibration related to braking, is everynow and then, when I step on the brake and the car is stopped up a slight incline, the vibration stops, and then when I let go, it returns. Weird, but that's whats happening to mine anyway.

[Maughany]

ahh ok mate yeah i think mine is a little more serious than that but also alot more of an intermittent problem i notice it only really happens when the economy button is on rather than power and maybe its once a week im thinking its when its trying to get into first gear on slow down to a halt im hoping its something simple like a pulley seizing up a little and not a rooted gearbox/stall converter problem.
but cheers for the reply mate

[Hodge]

ahh ok mate yeah i think mine is a little more serious than that but also alot more of an intermittent problem i notice it only really happens when the economy button is on rather than power and maybe its once a week im thinking its when its trying to get into first gear on slow down to a halt im hoping its something simple like a pulley seizing up a little and not a rooted gearbox/stall converter problem.
but cheers for the reply mate

No trouble at all mate. Hope it works out for you.
When I first noticed mine it drove me nuts for ages, as I couldn't replicate the problem to find out what it was. Took me ages to figure out it only happened after car was pushed a little bit...
I'm not mechanically minded enough to even begin answering what could your issue be, especially in autos. Have you checked the oil in the auto ???

[Maughany]

hey mate yeah i here ya i fitted the 3" exhaust on sunday morning last week and it was rattling on one spot doing my head in so fixed it the next night after work, now after alot of driving this weekend its slighlty rattling at the rear tail piece from sliding across on the rubbers gotta sort that out nothing worse that a rattling noise haha.
the oil in the auto is fine and i have new filters and fan belt on the way atm waiting for it to be delivered and ill give it a service next weekend and hope it sorts it out, if not i will start the enjoying process of trying to diagnose it lol

[Hodge]

hey mate yeah i here ya i fitted the 3" exhaust on sunday morning last week and it was rattling on one spot doing my head in so fixed it the next night after work, now after alot of driving this weekend its slighlty rattling at the rear tail piece from sliding across on the rubbers gotta sort that out nothing worse that a rattling noise hahal

Mine is somewhere around the gearbox area or after... When it does it, it resonates so loudly it's hard to pin point where exactly it's coming from. Putting something up against it stops it. But I cannot see it contacting anything metal at all. One day I'll get the culprit!

[Maughany]

Mine is somewhere around the gearbox area or after... When it does it, it resonates so loudly it's hard to pin point where exactly it's coming from. Putting something up against it stops it. But I cannot see it contacting anything metal at all. One day I'll get the culprit!

Wellllllll i believe i may be able to help you somewhat with this. my first drama with the exhaust rattling was because the is a bracket on the side of the gearbox which has a mount for the exhaust, now my bracket for the new exhaust was roughly 3mm off so i couldnt get the bolts in again but i seemed to have enoughed clearance so i didnt stress but what was happening was without that bracket being bolted to the gearbox mount the flexible join in the exhaust had shifted over about 10mm towards the gearbox tunnel and was rattling on there. now the bolts there are an absolute f**k to get to and i found it best using a ratchet spanner but because its so hard maybe have a look if they have bolted it back in or if there is eve a bracket on that system to bolt it into the factory position again.

so if you slide underneath the car level with the gearbox support bracket you should see the flexible mesh join, see if that has enough movement left and right to hit on the underbody??

[Hodge]

so if you slide underneath the car level with the gearbox support bracket you should see the flexible mesh join, see if that has enough movement left and right to hit on the underbody??

Just popped open another stubby, and will go get the creeper out and have a look at this !

[Maughany]

yeah let us know how you go, you will see the bracket for the exhaust on the passenger side of the gearbox tucked right up near the top of the tunnel towards the front of the car side of the gearbox support bracket which runs from one side to the other of the gearbox tunnel. confusing to read but ill take a pic and post it for you if you cant find it :)

[Hodge]

Is this it mate? If so mine is pretty solid. Although I need to check it when is hot and actually rattling. It's the bracket coming off the exhaust and goes up and tucked away next to gearbox. getting dark here hard to see 100%.

[Maughany]

yeah mate that's it my bracket was designed differently but basically yeah i found it was rattling from that area to the side of the tunnel.

[Hodge]

I'll take a closer look tomorrow and put a spanner to everything relating to exhaust.
My rattle is loudest if it's hot, and when I arrive home. My driveway has a bit of an incline. So once I park the car, it sit's pointing upwards somewhat. The moment I stop I can hear the rattle big time while holding the brake. Then, putting on the hand brake, and releasing the brake the car settles a bit backwards and the rattle goes completely away.
So something along the driveline becomes fully rested against the exhaust that dulls the rattle away.

[Hodge]

Also in regards to your issue mate, I recommend you create your on post/thread about it, as you'll get more views that way , surely somebody might have an idea.

[Maughany]

yeah very interesting might even be from the the s-bend from the turbo going to the underbody, once warm and on the slight incline + the torque on the driveline while in drive might shift the exhaust just enough to kiss the body, hopefully it is something able to be tightened or cut and re-bolted(which was my case) and not just a flaw in the exhaust making it too close. mate of mine who fitted exhausts for 5 years was saying whole sale they would get 15% off from buying an exhaust if they had a pipe bender on site so they could make slight adjustments without the need to send them back, as he said 95% of pre made exhaust were not a perfect fit.

[Hodge]

95% of pre made exhaust were not a perfect fit.

Definitely. Every car of same make and model is identical, yet different.
I had the same issue with my D22, which also had a rattly Beaudesert exhaust. Was banging loudly against the firewall. Had to take it off the turbo, do some bending and re-fit. And to get to the back of the turbo on the new 2.5L D22's is not a nice task.
Which reminds me my Patrol rattle also happens a lot when in reverse, so putting some strain on the driveline that way.

[Maughany]

Which reminds me my Patrol rattle also happens a lot when in reverse, so putting some strain on the driveline that way.

yeah that makes me think the problem maybe there rather than next to the gear box, also just a thought there was another bracket on mine that mounted to the side of the engine block which once again was a couple mm from lining up so i took to it with a grinder and cut it of not sure if your system will have that or not?