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-   -   960: Brakes help (https://forums.tbforums.com/showthread.php?t=338143)

stiligFox 12-06-2017 03:04 AM

Brakes help
 
Hello all! Having some brake issues that I would like to finally get fixed as I'm tired of having so many scares!

I had the pads and rotors replaced recently, but I don't know what brand my mechanic used. My other mechanic said that they are very hard rubber pads, but about 90% of them are left. I want to replace them because my braking distance is atrocious; it's about half of that of my 1997 S90 or even my dads 1990 F150! I can stop about 4 car lengths shorter in any other car, and it surprised even my Mom who's driven 240s/740s/960s for the last 25 years...

Anyway my mechanic keeps telling me they are fine but I know they can be better. The rotors are warped the heck and back now even though they are new, because the pads are so hard. My mechanic won't turn them as he says the new style rotors are too thin, but I feel like I should probably just replace them as well. I'm also thinking about putting on iPD stainless steel brake lines since A) the original lines are likely old by now and b) the IPD lines are cheaper than getting new Volvo ones!

The other issue I've begun to notice is that when I first start driving, I'll put the car in reverse to leave the house, and I feel a sharp pulsing in the brake pedal for a few yards; it feels sort of like chest congestion in the brake line. While I'm driving every now and then there will also be a soft thud in the brake system. Any idea what these might be? Could it be the ABS sensors getting old?

My main question for the moment I guess is; what brake rotors and pads do you all recommend for good quick stopping power? I'm not doing any racing, but are slotted rotors of any particular help?

Thanks for the advice guys!!

DET17 12-06-2017 07:32 AM

I think your 92 likely has the same front brakes as mine. When I first resto-modded mine, I converted all 4 corners to Zimmerman rotors and a "medium aggressive" pad, like a PB Metal master or similar. I have just removed that front setup and upgraded to 302mm front rotors and later 850 calipers. One of the key improvements I discovered (via the web, not yet experience) is the AKEBONO pads (spelling suspect, not much coffee yet). The reviews on these are excellent; search and you'll see what I mean.

All that said, the early 9 series brakes leave a lot to be desired. Mine have always had normal function, but never impressed me; I'm expecting better performance with the upgrade. The 95+ vehicles in the 9 series family got a braking upgrade, which is claimed to significantly help (details in my build thread).

Since your vehicle is basically stock, I'd get new rotors (my Zimmermans are available) but the key thing will be the improved pads. Beyond that, you're going to spend much more $$ trying to improve the system. Are you sure your brake booster (servo) is working properly?

Janspeed 12-06-2017 08:22 AM

double post, sorry

Janspeed 12-06-2017 08:22 AM

Your post does not mention what car. i assume it is the '92 965 in the sig.?
A car from 1992 is old... and it is a good idea to do a complete overhaul on the brake system because all parts will be old.

Brake pads are never made of rubber... any pad that's available for streetuse should work OK. (Racing pads might need to warm up to perform properly, they are not very suitable for streetuse)
And new rotors will not warp easily , specially not it the brakes perform badly (= not able to put heat in the rotors! Rotors warp because of excessive heat and temperature shocks)
New rotors should be installed on clean rustfree boltflanges. Any rust on those can cause the brakes to feel like they are warped. (attention to detail matters)
On a 900 (and 700) it can also be the case that the mushroom bushings in the lower control arms are shot. Very common problem on these cars. Also the cause of weird movement in the front suspention when driving backwards. These can also be the cause of brake judder and making the brakes feel like the rotors have warped when in fact they are not.

about ABS sensors: they do not wear, they either work (= produce an electric signal) or they don't.
however, It sometimes does happen that corrosion on the ABS tooth rings or debris on the tip of the ABS sensor cause bad signals = problems for the ABS.
It's a good idea to clean the toothrings and sensor ends to ensure proper functioning. The (only!) sensor for both rear brakes is in the rear diff cover.

don't fixate on the pads and rotors. (unless they are obviously totally worn out but that's easy to see). Slotted rotors will not increase the brake performance at all. They are there for cooling and expelling gasses coming from hot pads. Not needed on any road car. The stock brakes should be able to provide plenty of stopping power.

Instead make sure the entire brake system itself is functioning 100% (your post suggests that there is something seriously wrong, a well sorted stock 900 should be able to brake really hard.)

- it is smart to change old rubber flex hoses. They can cause all kinds of annoying and potentially dangerous problems. (internal swelling, cracking due to dryrot causing fluid leaks) if in any doubt, change them.
- the front calipers do 70+% of all brake work. So, if you are disappointed about the performance start by checking the front brakes first for quick wins. Make absolutely sure those front calipers are working perfectly. Make sure all pistons can move freeling inside the caliper, that the pads are not stuck on the edges inside the caliper (remove debris/crud/rust), that they can move freely along any slidepins. Here attention to detail matters.
- Brake fluid is hydroscopic, it attracts water. old brake fluid will have captured water in it. This water will easily boil inside the brake fluid. Boiling water turns into compresseable steam... these steam bubbles prevents you from putting proper pedal pressure on the brakes. That's why you need to flush the system with clean new fresh DOT4 brakefluid and make sure to bleed the system perfectly. Start bleeding the rear brakes first en move your way to the front brakes.
(be careful not to snap any bleednipples. Remove rust with a small wirebrush, give all bleednipples a shot of penetrating oil. Give all bleednipples a light tap on the end to shock them lose. only then try to open any of those for bleeding. If you snap one off you have an annoying problem...
- bleeding tips: tap the calipers to shake lose any trapped airbubbles. Then bleed again. If you keep having problems bleeding the system, try jacking the car up at the end where you want to bleed. It could help air to reach the high point (= your bleednipple) easier.
Brake bleeding can be done with a helper but easybleed toolkits are not very expensive and will make it a oneman job.
- With the engine running check if the brake booster is able to hold vacume , check if the oneway valve inside the brakebooster hose still functions like it is supposed to.

If everything is OK after checking/correcting and you still have a soft pedal that does not hold pressure then you might have a worn (internally leaking) master cilinder. Replace... and bleed the entire system again...

finally: in the whole equasion of braking the TIRES also play a crucial role. If the tires are old the rubber compound will have hardened. (check the 4digit production date code on the sidewalls of the tires) Your car can have perfect brakes but if the brake forces can't be transmitted to the road then the car will not perform very well. The tires will lose grip early while braking and ABS will prevent the wheels from locking up by releasing brake pressure (you can hear and feel it in the pedal)... increasing brake distance...
Fresh new grippy tires will reduce your brake distance.
At least make sure you optimise tire grip by using the right tire pressure (when i had my 940 i found 2.5bar/36psi to be optimal on 205/55x16 and for 195/65x15 i used 2.4bar/35psi for optimal grip.

stiligFox 12-07-2017 05:28 PM

Thank you for all the advice!! I'll start by checking the things you mentioned. Dad was thinking to check for vacuum too, I'll do that as soon as I get her back from the shop. The only reason I was thinking that the rotors are horribly warped is because when I was driving on a freshly paved stretch of highway here in town, she sailed along so smoothly until I slowly put on the brakes, when I could feel a shudder going through the pedal like a foot massage...

My mechanic just called today and said he's replacing the ball joints to help fix a steering noise issue, could that be related?

I'll definitely check the front brakes out, and try cleaning up those, as well as a brake line flush. Might go ahead and re do the lines because these ARE 25 years old! Then will check the brake booster vacuum and go from there...

I do need new tires as... mine are about 5 or 6 years old and the rubber is definitely hard from sitting in the Texas heat; we're going to replace those too in the next couple months.

freevolvos 12-09-2017 12:58 PM

the metal lines should not need replacing unless Rusty. rubber hose yes. and you can bench bleed the master so you don't have to rebleed the whole system

VB242 12-09-2017 02:23 PM

Quote:

Originally Posted by freevolvos (Post 5717278)
the metal lines should not need replacing unless Rusty. rubber hose yes. and you can bench bleed the master so you don't have to rebleed the whole system

Huh? There's air introduced in the lines when you disconnect them from the MC, you still have to bleed them, but you also have to bench bleed the MC.

stiligFox 12-15-2017 04:49 AM

OY! Got her back and it’s gone from bad to worse...

ABS light comes on, and I can feel all kinds of popping and groaning when coming to a stop. Speedometer is rapidly fluctuating within +/- 5mph of my real speed. The OBD port under the hood isn’t even registering that the ABS computer exists... I’m going to check the rear speed sensor for the speedo and the over voltage relay for the ABS computer.

Any thoughts? What should I clean the ABS sensors with?

kzoc 12-15-2017 09:41 AM

Who did you take it to?

Only one RWD person in town that would get my business...

stiligFox 12-15-2017 11:01 AM

Quote:

Originally Posted by kzoc (Post 5720154)
Who did you take it to?

Only one RWD person in town that would get my business...

Took it to Redline - Troll swapped both sway bars, replaced the front ball joints, tightened down a lot of stuff. I took her in for knocking while turning in place but it still does that some; new ball joints really tightened up the steering though! Having him check the brakes was a secondary thing and he said they feel fine while the ABS wasn’t working. Going to give him a call today and see if he had noticed the speedo not working when he was testing stuff.

I only trust Cap-V and Redline around here...

stiligFox 12-21-2017 01:42 AM

Okay - so I think I'm pretty sure I found the issue for the speedo and ABS light - the rear wiring harness leading into the speed sensor is completely falling apart; near the plug there is zero insulation and the exposed wiring is green with corrosion. Surprised it's working at all this point! So looking into getting a replacement relay if anyone actually still has it, or I'll make my own.

The ABS is still acting way funky though. Whenever I come to a stop, I feel the system trying to test the system; there's a lot of pulsing going on and I can hear groaning from under the hood. The ABS light will sometimes come on, but I can't pull any codes from the ABS computer; somehow the link between the diagnostic unit and the ABS computer is broken. Does anyone know what I should check to fix this, so I can at least start pulling codes?

DET17 12-21-2017 07:39 AM

Better find the greenbook detail for ABS on your vehicle. Next best online resource.... the 700/900 Maint. Pages from the UK Volvo Club. Search, and ye shall find.......

Janspeed 12-21-2017 07:46 AM

Quote:

Originally Posted by stiligFox (Post 5720175)
Took it to Redline - Troll swapped both sway bars, replaced the front ball joints, tightened down a lot of stuff. I took her in for knocking while turning in place but it still does that some; new ball joints really tightened up the steering though! Having him check the brakes was a secondary thing and he said they feel fine while the ABS wasn’t working. Going to give him a call today and see if he had noticed the speedo not working when he was testing stuff.

I only trust Cap-V and Redline around here...

speedo uses the ABS sensor in the Diff cover. Your ABS-brake problem may be related to the speedo not working.

Janspeed 12-21-2017 08:03 AM

Quote:

Originally Posted by stiligFox (Post 5722745)
Okay - so I think I'm pretty sure I found the issue for the speedo and ABS light - the rear wiring harness leading into the speed sensor is completely falling apart; near the plug there is zero insulation and the exposed wiring is green with corrosion. Surprised it's working at all this point! So looking into getting a replacement relay if anyone actually still has it, or I'll make my own.

The ABS is still acting way funky though. Whenever I come to a stop, I feel the system trying to test the system; there's a lot of pulsing going on and I can hear groaning from under the hood. The ABS light will sometimes come on, but I can't pull any codes from the ABS computer; somehow the link between the diagnostic unit and the ABS computer is broken. Does anyone know what I should check to fix this, so I can at least start pulling codes?

seems you have found a real problem . Wiring should not be exposed. Start by fixing that issue before changing any relay.

about diagnostics: Each sub-system (fuel, ignition, ABS) uses it's own terminal. have you stuck the pigtail in the correct ABS-terminal? https://www.matthewsvolvosite.com/wp...40-gearbox.gif

i still think you should flush the brakefluid and do a good bleeding session.
Brake fluid that is older then , lets say 4 years is OLD and no bueno.
When i was still a rally mechanic we flushed brake fluid every friggin' rally! Just to be absolutely 100% sure that the brakefluid was good and that there was no air in the system at all. This ensured dependable brakes even when they are glowing red from the heat.

stiligFox 12-21-2017 04:24 PM

Quote:

Originally Posted by Janspeed (Post 5722783)
seems you have found a real problem . Wiring should not be exposed. Start by fixing that issue before changing any relay.

about diagnostics: Each sub-system (fuel, ignition, ABS) uses it's own terminal. have you stuck the pigtail in the correct ABS-terminal?

i still think you should flush the brakefluid and do a good bleeding session.
Brake fluid that is older then , lets say 4 years is OLD and no bueno.
When i was still a rally mechanic we flushed brake fluid every friggin' rally! Just to be absolutely 100% sure that the brakefluid was good and that there was no air in the system at all. This ensured dependable brakes even when they are glowing red from the heat.

Okay - will fix that asap. The wiring harness is NLA but it's just a pair of twisted wires, will be an easy repair.

I did check to make sure the post was correct; the engine and transmission ports both light up dully when the probe is inserted and brightly when the button is pushed - and they both return 1-1-1 codes. The ABS port doesn't light dully at all but the test light does come on when pushing the button, but it doesn't return any codes.

I guess I could redo the brake fluid; it's been 12,000 miles and 2 1/2 years since I had the brakes done all around and flushed.

stiligFox 12-21-2017 11:04 PM

Harness pics: https://imgur.com/a/I7QVY

Well shoot, I got the harness apart and fixed up but now the speedo isn’t working at all - just registers 0mph and of course the ABS light is on.

Will diagnose tomorrow and see if the wires are still getting connectivity all the way through.

In the rear fender well where the ABS harness connects to the main harness, the connectors are sealed up in a plastic box. I’m guessing this is for security reasons (preventing tampering?) but does anyone know how to get the box open without destroying it?

Janspeed 12-22-2017 05:45 AM

double post

Janspeed 12-22-2017 05:48 AM

maybe check if the ABS system uses a fuse. Maybe it is blown? caused by those naked wires.
If you have fixed those wires and if you have located a blown fuse just try a new fuse and see if the diagnostic port is working again, then erase any existing error code.
Then drive and see if the code stays away.

stiligFox 12-22-2017 02:42 PM

Quote:

Originally Posted by Janspeed (Post 5723355)
maybe check if the ABS system uses a fuse. Maybe it is blown? caused by those naked wires.
If you have fixed those wires and if you have located a blown fuse just try a new fuse and see if the diagnostic port is working again, then erase any existing error code.
Then drive and see if the code stays away.

Ah good point, maybe while I was working on it I blew something. Cheers! I'll check that; I was about to tear the whole harness apart again haha

stiligFox 12-27-2017 05:47 PM

Okay! Good news - I found the problem, and repaired it temporarily!

Stripped everything off the wires and found that the brown wire was broken clean through half way up the harness:

https://i.imgur.com/TDVQnP5l.jpg

Fixed!

https://i.imgur.com/pdQhmgCl.jpg

It's missing some of the protective cover now, but only on the part that's inside the car. The copper wire is corroding badly inside; I cut the white/green wire in the same place as well to add heat shrink where it was needed, and the copper was black. The copper is black all the way through the whole harness! Anyway, after soldering the wires back together (and burning off some nasty smelling corrosion there) the harness is working fine for now!

A side affect of this is that the ABS isn't constantly testing itself at every stop, and the popping and groaning is gone.

I still can't get and signs of life at the diagnostic computer though; I guess I'll have to trace the diagnostic line back to the ABS computer and look for any breaks there...


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