Rythmic thud at 70mph...weird

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musky81

Active Member
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Having managed to get the new prop shaft bearings on before christmas was very pleased. Also managed to get new discs and pads done...mintex,.what an improvement.
Anyway having done a christmas card run, up and down dual carriageway, down country roads etc was feeling very pleased with all beibg sorted. Then on way back along dual carriageway, 70mph for few minutes and I started to hear this rythmic thud....faint but there. Eased off the gas, it went, sped up again and all fine. Went back along after roundabout to check again and all ok. Note discs and pads still bedding in. Prop shaft was put back same way as it came off. Just wondered if anyone had experienced anything similar? A one off for some reason?
 
hi check the front joint onto the gearbox, make sure the boot isn't split and lost its grease ,this causes a drumming in and out at about that speed, gives you headache on a long run, if it has don't let garage tell you, you need front section cos you cant get replacement boot, YOU CAN !!!!!!!!!!!!!! £28 not £400 for front section, hope this helps
 
we`ve had this happen 3 times now if it has gone and you fit it don't over stretch new boot when fitting....
 
Thanks for your info. Just done another check and its the brakes. I though i was having bedding in issues but it seemsive got a sticky caliper thats not retracting. The nearside disc is heating up and warping. The thudding started about 2 or 3 mins after getting to 70mph then when I touched the brakes I could feel the pulsing through the pedal and steering shaking. Itscooling down againat slow speeds and brakes are fine then, no pulsing so no permanent warping luckily....yet.
 
And the issue is caused by using copper grease on the sliding pins and the rubber swells up and causes the caliper to stick and not restract properly
 
Interesting info thanks, pondering whether to order overhaul kit or just get a new caliper. Sliding pins were free when I put new discs and pads in so looks likely piston/seals.
 
jamesmartin said:
if piston pushes back and slides are free then its another issue
Click to expand...

I plan to take out piston tomorrow and check. There were no issues before changing out other than the pads being worn and slight scraping due to corrosion on disk outer circumference. No problems with overheating. Since I changed discs and pads the nearside been hot after runs...hotter than offside. I had a similar problem with a bmw few years back where brakes were sticking on and this was resolved by cleaning pistons. The calipers retracted ok but not really sure if it felt tight or not as I was using a crappy g clamp which made it awkward anyway. I, ll start with re check of caliper and post findings.
 
So..for closure on this issue in case a similar thing happens to anyone else. Went through things one at a time to try to pinpoint problem. All caliper slides were cleaned and regreased, no damage found and all free to slide. No difference on test rub, near side brake getting much hotter than off side and same thudding occurred after few mins at 70mph. Back to the garage and removed pads and shims and cleaned, removed rust build up and regreased all parts to ensure pads would not become jammed in calipers. Again no improvement on test drive. On checking caliper piston movement, found nearside piston was a lot harder to retract than offside using small g clamp. Pushed the nearside piston out using the hydraulics to the end if travel and carefully pulked back the dust seal. Found that indeed the end of the piston had corrosion close to the dust seal recess and some build up of crap around the surface. Cleaned all up using scotch nylon pad til satisfied and re assembled. The piston now pushed back much easier, similar to offside. System bled again. Road test all good and no more hot brakes, and no annoying thud.
 
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