3 issues - Clunk when braking + exhaust fumes + soft brake pedal after track

[Dominic]

Guys,
I have one issue that is new to me and others that I've observed since I've had the car.

New issue - When I apply the brakes, I hear a single clunk that sounds like it's coming from the left rear of the car. When I release and then reapply the brakes, I hear the clunk again. Any ideas on what to look for?

Old issue #1 - I get exhaust fume smells in the car whenever I have any window open, either side or the sunroof. I used to have a torn vent flap in the trunk, but I replaced it and the smells still occur. I don't notice the fumes when driving around with all the windows closed. Additional info that might be helpful - the bulkhead behind the rear seat was cut out by some crazed speaker installer in the past. I now have a rear seat installed, but I do have holes cut in the seat for my roll bar tubes that pass through into the trunk (don't worry, I picked up a regular e30 seat to cut up).

Old issue #2 - My brake pedal seems to go soft after a single day on track. I'm using ATE fluid (super blue or typ 200) which is supposed to be good stuff, but it seems that I get air in the system, presumably from boiling the fluid, after just a couple sessions on track. I wouldn't think this quality fluid should boil that easily. I'm running stock rotors, calipers, and guide pins, with Hawk HT-10 pads. I do have brake ducts, with a hose running to the backing plate. I don't have a fancy backing plate, but I have cut an opening in the stock plate. If I bleed the brakes, the pedal comes back up, so it does seem to be an issue with air in the fluid somehow. Any thoughts?

It has been awhile since I've posted any questions and as always I appreciate your help.

Thanks guys!

[JZM3]

issue #2

not sure if this will help but I have the same problem, found a really small exhaust leak that I am going to get welded which we think is the culprit.

also I found this thread today
http://www.s14.net/forums/showthread...t=sunroof+seal

[Mmark]

#1 Look into an exhaust leak or a clogged/leakingVapor recovery system (fuel tank to evap canister).

#2 Look into glazed front pads... Unusual but possible. If you are not using Race pads at the rear, get some.
Bleed, bleed , bleed again with NEW fluid from an unopened container.
Get another set of front HT10s

Watch out for a failing brake master cylinder.

m

[mtony]

Probably have some issue with pads or sticking calipers, but if not, I would use a better brake fluid such as Motul RBF 600. My e46 M3 is hard on brakes at the track and the ATE Super Blue was no better than the stock brake fluid at the track. I changed to the RBF 600 and have not had any problems since.

[Dominic]

I do in fact have some exhaust leaks that I'm aware of. There is a little bit of soot that I can see near the welds at the bottom of the header near the flange, so there's a small leak there. I also have a leak where I installed my Stromung muffler to the stock center section. The spacing between the pipes is so small that I couldn't fit a real clamp there, so they're just basically pressed together with hose clamps. Any suggestions on where to find a quality thin clamp that will fit and seal? Will any slight exhaust leaks under the car result in fumes inside?

I'm familiar with the evap canister near the power steering reservoir. How can I check to see if it is clogged or leaking?

For the soft pedal issue, bleeding definitely corrects the problem when it occurs, but what surprises me is how quickly the problem comes back when I get on track. Just a few driving school sessions and at the end of the day I'll notice the soft pedal. This has happened with several different sets of pads over time. I used to run the Turner Motorsport Cool Willy pads, and now I'm running HT-10s. I have wondered whether the master cylinder could be contributing. How can I tell if I have a failing master?

I don't know when my calipers were last rebuilt, so I suppose I ought to go ahead and rebuild them to make sure they're up to snuff. I think they're ok because I have even pad wear on both sides of the car. Surprisingly the rubber boots seem to be holding up to the heat so far. Has anyone else needed or found "upgraded" caliper boots designed to better handle the heat from track work? I was wondering if the ATE just isn't holding up, but lots of people run it without issue I think. I was hoping to avoid having to go to the really expensive Motul fluid.

[M3 Adjuster]

Change your fluid to a better fluid.. by your location, I presume you are running some decent tracks like VIR, and/or Road Atlanta.. ATE Super Blue/Type 200 is to brake fluid as Hawk HP+ is to brake pads... Essentially it's a step up over stock fluid that's good up to intermediate use. There are some very advanced drivers and even racers that continue to use ATE and make bleeding the calipers at the track a daily procedure as part of their track regimen. If that's your style, then that's fine...Personally, I'm not sure how one can be continually using an unopened can of fluid though, and do this method... ??

So.. you can continue to flush OFTEN, (which is fine, it's just your time involved) or you can step up to a better fluid and make your life easier. I personally use Castrol SRF, and I flush my brake fluid on an annual basis.. For DE purposes, always within the last six month of course! SRF is something like $80 a liter, but if you look at it's wet boiling point vs the dry boiling points of other fluids, and you will see how impressive it is! Either you pays a little and bleed often, or you pays a lot and you have little maintenance at all... I'm admittedly lazy, so the choice is easy for me, but I'm not complaining about my brakes either HAHAHA! :smile2:

Motul RBF 600 is a good step up and is relatively inexpensive. It has higher wet and dry temps and I think it even comes in half liter bottles, which is good for the frequent bleed types... At the very least I would change to this and see if the issue goes away or not.

It's possible that adding track pads in the rear may reduce some of your front braking, but if you are happy with your driving/braking style, it's not necessary in my opinion. Many people drive with more aggressive pads in the front than the rear, including me!

[AndrewK]

Hey Dominic, soft brake pedal or not you were running some quick laps last weekend! Congrats again on winning the Time Trial both days! I had a blast running with you that one session and we definitely need to do that again. First, post your on-board so I can figure out how you kept catching me at Hogpen. haha

I would start with a caliper rebuild all around. Easy job and you may be surprised what you find inside the caliper. I've found some nasty goo in previously neglected brake systems even though the fluid was coming out clean. The stock caliper boots will hold up fine. There's a trick to installing them so they won't pop out. Look into the stainless pistons from Bimerworld. As for brake fluid I'm one of those advanced guys still using SuperBlue. I've never had a problem, but maybe I need to man up and use the brakes harder! My friend Jason (was at VIR with me) did have problems with SuperBlue in his e36 and recently switched to RBF 600. He's happy with the switch and says his brakes have never felt better. Although we did shave over 500lbs out of his car this winter. :tiny:

As for the clunk I assume it's not something loose in the trunk? Have you checked the usual suspect...shock mounts? I'd also check sway bar links/mounts, exhaust hangers, and put a torque wrench on everything within reach. If I'm not mistaken your subframe mounts and trailing arm bushings are all relatively new?

[UNHCLL]

If your main trunk lid gasket is torn/worn you may also get exhaust fumes in the car.

[BingM3]

Guys,
I have one issue that is new to me and others that I've observed since I've had the car.

New issue - When I apply the brakes, I hear a single clunk that sounds like it's coming from the left rear of the car. When I release and then reapply the brakes, I hear the clunk again. Any ideas on what to look for?

Old issue #1 - I get exhaust fume smells in the car whenever I have any window open, either side or the sunroof. I used to have a torn vent flap in the trunk, but I replaced it and the smells still occur. I don't notice the fumes when driving around with all the windows closed. Additional info that might be helpful - the bulkhead behind the rear seat was cut out by some crazed speaker installer in the past. I now have a rear seat installed, but I do have holes cut in the seat for my roll bar tubes that pass through into the trunk (don't worry, I picked up a regular e30 seat to cut up).

Old issue #2 - My brake pedal seems to go soft after a single day on track. I'm using ATE fluid (super blue or typ 200) which is supposed to be good stuff, but it seems that I get air in the system, presumably from boiling the fluid, after just a couple sessions on track. I wouldn't think this quality fluid should boil that easily. I'm running stock rotors, calipers, and guide pins, with Hawk HT-10 pads. I do have brake ducts, with a hose running to the backing plate. I don't have a fancy backing plate, but I have cut an opening in the stock plate. If I bleed the brakes, the pedal comes back up, so it does seem to be an issue with air in the fluid somehow. Any thoughts?

It has been awhile since I've posted any questions and as always I appreciate your help.

Thanks guys!

Also lift your shift boot and see if any fumes may be coming from there, common.

[Mmark]

Hey Dominic, soft brake pedal or not you were running some quick laps last weekend! Congrats again on winning the Time Trial both days! I had a blast running with you that one session and we definitely need to do that again. First, post your on-board so I can figure out how you kept catching me at Hogpen. haha

you're obviously(now) fast enough to win with an old car, so you need more brakes.
1,Get backing plates to maximize the efficiency of the brake ducts.
2, you need more pad all around, plus look into the caliper rebuild suggestions.
3, You'll need better brake fluid, to cope with the high front brake temps.

m

[Dominic]

If your main trunk lid gasket is torn/worn you may also get exhaust fumes in the car.

Also lift your shift boot and see if any fumes may be coming from there, common.

Good ideas guys, I'll visually check both those areas.

Change your fluid to a better fluid.. by your location, I presume you are running some decent tracks like VIR, and/or Road Atlanta.. ATE Super Blue/Type 200 is to brake fluid as Hawk HP+ is to brake pads...

I love VIR. :heart:
I never thought about ATE that way but it's a perfect way to put it into perspective. Thanks!

you're obviously(now) fast enough to win with an old car, so you need more brakes.
1,Get backing plates to maximize the efficiency of the brake ducts.
2, you need more pad all around, plus look into the caliper rebuild suggestions.
3, You'll need better brake fluid, to cope with the high front brake temps.

m

I'm going to look into all these things, and trying out some better fluid is at the top of the list. I was actually hoping that the issue was that I was simply overtaxing the abilities of the ATE and I'm glad to hear some independent confirmation that it seems to be the case.

Hey Dominic, soft brake pedal or not you were running some quick laps last weekend! Congrats again on winning the Time Trial both days! I had a blast running with you that one session and we definitely need to do that again. First, post your on-board so I can figure out how you kept catching me at Hogpen. haha

I would start with a caliper rebuild all around. Easy job and you may be surprised what you find inside the caliper. I've found some nasty goo in previously neglected brake systems even though the fluid was coming out clean. The stock caliper boots will hold up fine. There's a trick to installing them so they won't pop out. Look into the stainless pistons from Bimerworld. As for brake fluid I'm one of those advanced guys still using SuperBlue. I've never had a problem, but maybe I need to man up and use the brakes harder! My friend Jason (was at VIR with me) did have problems with SuperBlue in his e36 and recently switched to RBF 600. He's happy with the switch and says his brakes have never felt better. Although we did shave over 500lbs out of his car this winter. :tiny:

As for the clunk I assume it's not something loose in the trunk? Have you checked the usual suspect...shock mounts? I'd also check sway bar links/mounts, exhaust hangers, and put a torque wrench on everything within reach. If I'm not mistaken your subframe mounts and trailing arm bushings are all relatively new?

Caliper rebuild with SS pistons is going on the to do list. You're right about the bushings all being new. I will check the shock mounts and tighten everything in sight, good suggestions. By the way, thanks again so much to you and your lovely wife Erika for helping me bleed the brakes Sunday morning! I'm sure she was happy to have beautiful weather for her 2nd DE.

As far as the video, unfortunately I ended up with pretty crappy images and not much from that session. It was an amazing session and I was hoping to share it with folks here who would appreciate two real M3s carving through high horsepower traffic. Sadly I only got one lap of us running together before the camera battery died, and it's when we're still stuck in traffic. Here's what I did get:



I also cut down a quick clip of the more interesting part of the time trial session when I started to catch some cars from the back of the group:




Thanks again for the input guys.

[jht3]

1: a) check your caliper mounting bolts. all four. use red loc-tite for the saddle mount bolts.
b) check your diff bolts

2: not sure. i've had exhaust leaks but never smelled it in the car. i also have no rear deck and a torn shift boot and still no smell

3: i've never had a "soft" pedal like how i would describe brakes going away, but i've had a low pedal that i didn't like. i changed the brake master and adjusted the pedal freeplay with remarkable success in fixing my pedal. it may have been one or both, i don't know. but no matter what pads, age of rotors, fluid type, or mass bleeding ever fixed the issue.

[junkyard_sal]

I am bumping this old thread.

I have issues 2 & 3 on my track car. I am planning to replace the shifter boot and the trunk seal. How do I determine if the vapor canister is plugged or if the line is clogged? I have a new Supersprint header back exhaust on the car.

On the brake issue, I rebuilt my front calipers after Oktoberfest and installed the brass bushing kit. The driver's side needed it but the passenger side was good (but rebuilt anyway, it was good to see the difference between a failing caliper and a good one). I still use Ate type 200 (just changed, complete flush on rebuild). After a hard weekend at the track my brake pedal is definitely longer and softer. For added information, on the drive home I heard what sounded like a bit of brake dragging howl from the driver's front when speeds were in the 80-90 range(Maybe I did not get it clean enough on rebuild?). How do I tell if I have a failing master cylinder? Lines are in good shape and braided stainless. Pads are HT-10s New in front, older in rear). Final piece of information during the tech inspection, we noticed that the driver's front wheel turned with the brakes off but required more input than we thought it should. Wheel bearings are solid and are new this year.

[RDCD12]

Guys,
I have one issue that is new to me and others that I've observed since I've had the car.

New issue - When I apply the brakes, I hear a single clunk that sounds like it's coming from the left rear of the car. When I release and then reapply the brakes, I hear the clunk again. Any ideas on what to look for?

Old issue #1 - I get exhaust fume smells in the car whenever I have any window open, either side or the sunroof. I used to have a torn vent flap in the trunk, but I replaced it and the smells still occur. I don't notice the fumes when driving around with all the windows closed. Additional info that might be helpful - the bulkhead behind the rear seat was cut out by some crazed speaker installer in the past. I now have a rear seat installed, but I do have holes cut in the seat for my roll bar tubes that pass through into the trunk (don't worry, I picked up a regular e30 seat to cut up).

Old issue #2 - My brake pedal seems to go soft after a single day on track. I'm using ATE fluid (super blue or typ 200) which is supposed to be good stuff, but it seems that I get air in the system, presumably from boiling the fluid, after just a couple sessions on track. I wouldn't think this quality fluid should boil that easily. I'm running stock rotors, calipers, and guide pins, with Hawk HT-10 pads. I do have brake ducts, with a hose running to the backing plate. I don't have a fancy backing plate, but I have cut an opening in the stock plate. If I bleed the brakes, the pedal comes back up, so it does seem to be an issue with air in the fluid somehow. Any thoughts?

It has been awhile since I've posted any questions and as always I appreciate your help.

Thanks guys!

For New Issue - Check the caliper and guide pins from where the noise is coming from. Clunking from brakes usually mean the caliper is on it's way or something is loose, ie; pads loose in pocket or bracket loosening.

Old Issue #1 - Check all the brake lines for any sign of a leak. If you find none and are bleeding it correctly, I would probably start with the master cylinder first and then see what happens.

[88_MMM]

As for the new issue I would check the dif bolts connecting to the inner CV. I had a clunk under braking and shortly after the axle disconnected at while driving scaring the Shi* out of me. After the repair there was no more click. I now torque these bolts every time I do an oil change.