Some of this has been touched on in other threads but there's never been complete resolution to a problem that isn't air/bleeding related.
What I'm going to be asking for here is if someone knows where I can obtain just the internal seals for the master cylinder so that I can contact them and beg them to post them in an envelope to me in the UK. I'm on my second MC from Rock Auto, certain it will fail as the other did, and the warrant is next to useless as It costs as much to return as buy a new one. So far, each MC costs me around £70 ($100) and last no more than a few hundred miles. (Rock Auto did offer repair kits but not currently showing on their site).
Brief recap and observation of the failures so far.
Original MC: the pedal would slowly sink to the floor with the engine running and stationary but always stopped the truck. One day it sank to the floor quickly but there were still brakes enough to stop.
Replacement MC from Rock Auto: same as before ie, the pedal would slowly sink to the floor with the engine running and stationary but always stopped the truck. This MC never completely failed and was replaced with another from Rock Auto (same Raybestos type as supposed warranty claim).
Second replacement MC from Rock Auto: same as before ie, the pedal would slowly sink to the floor with the engine running and stationary but always stopped the truck. Until last week when it failed in the manner of the original MC.
How it failed may be pointer to something other than being supplied with bad MCs.
I was sat in N holding it on the brakes (something I never usually do as I usually use the parking brake) to stop it rolling forwards on a slight incline waiting for a stop light to go green. For the next 2 miles I never touched the brakes (plenty twists but I just carried the speed) until I came to the end of my driveway and used them lightly to check the last bit of speed (I'd coasted in for the main part) for the tight turn. Right down to the speed the EVO starts giving full assistance and the pedal fell to the floor. And again on the driveway as I brought it to a halt.
Given that the pedal sinking (as far as I can ascertain as when braking at speed the truck will stop before any pedal sinking) is always at a speed where EVO fully boosts the steering, is there some connection there? Why is my truck killing MCs?
For now, I have the first Rock Auto replacement MC back in but I'm expecting it to fail completely also and re earlier warranty comment throwing new MCs at this isn't achieving anything.
Even if the MCs are bad, I'm not getting the warranty cover for replacements. One thing I'm convinced of is that while the Chinese can do some things well, they are rubbish at elastomers (eg, their driveshafts are mechanically good but the rubber boots fail in a year or two). Given the effectiveness of an MC is in its elastomer seals....
So, I have two MCs sat on the bench I could rebuild if I could get good quality seals. Any ideas?
And any thoughts on whether my problem is solely MCs with poor seals or is there the possibility my truck is killing MCs. Or the possibility of some other fault eg, ABS unit?
Calipers are fine (just rechecked them), new front hoses and slave cylinders. Not a bleeding issue - I know the difference between a springy air pedal and and fluid being forced through a tight gap in the manner of hydraulic damping - which is how the pedal feels. ABS operates as it should when pushed. (Don't have scan tool to bleed ABS unit but have had it operating and no difference. Anyway, ABS is out of the loop when pedal is sinking and not bleed issue). None of the MCs when removed showed any signs of external leakage, no other external leaks and fluid level never drops.
Apologies for then length of this post - but as you can appreciate, I need to get on top of this. Throwing a new ($100) MC at it every few hundred miles isn't a viable option. I need at least to be able to rebuild the MCs I have until a permanent solution (if better seals aren't the answer) is found.
Or are the MCs bad?
What I'm going to be asking for here is if someone knows where I can obtain just the internal seals for the master cylinder so that I can contact them and beg them to post them in an envelope to me in the UK. I'm on my second MC from Rock Auto, certain it will fail as the other did, and the warrant is next to useless as It costs as much to return as buy a new one. So far, each MC costs me around £70 ($100) and last no more than a few hundred miles. (Rock Auto did offer repair kits but not currently showing on their site).
Brief recap and observation of the failures so far.
Original MC: the pedal would slowly sink to the floor with the engine running and stationary but always stopped the truck. One day it sank to the floor quickly but there were still brakes enough to stop.
Replacement MC from Rock Auto: same as before ie, the pedal would slowly sink to the floor with the engine running and stationary but always stopped the truck. This MC never completely failed and was replaced with another from Rock Auto (same Raybestos type as supposed warranty claim).
Second replacement MC from Rock Auto: same as before ie, the pedal would slowly sink to the floor with the engine running and stationary but always stopped the truck. Until last week when it failed in the manner of the original MC.
How it failed may be pointer to something other than being supplied with bad MCs.
I was sat in N holding it on the brakes (something I never usually do as I usually use the parking brake) to stop it rolling forwards on a slight incline waiting for a stop light to go green. For the next 2 miles I never touched the brakes (plenty twists but I just carried the speed) until I came to the end of my driveway and used them lightly to check the last bit of speed (I'd coasted in for the main part) for the tight turn. Right down to the speed the EVO starts giving full assistance and the pedal fell to the floor. And again on the driveway as I brought it to a halt.
Given that the pedal sinking (as far as I can ascertain as when braking at speed the truck will stop before any pedal sinking) is always at a speed where EVO fully boosts the steering, is there some connection there? Why is my truck killing MCs?
For now, I have the first Rock Auto replacement MC back in but I'm expecting it to fail completely also and re earlier warranty comment throwing new MCs at this isn't achieving anything.
Even if the MCs are bad, I'm not getting the warranty cover for replacements. One thing I'm convinced of is that while the Chinese can do some things well, they are rubbish at elastomers (eg, their driveshafts are mechanically good but the rubber boots fail in a year or two). Given the effectiveness of an MC is in its elastomer seals....
So, I have two MCs sat on the bench I could rebuild if I could get good quality seals. Any ideas?
And any thoughts on whether my problem is solely MCs with poor seals or is there the possibility my truck is killing MCs. Or the possibility of some other fault eg, ABS unit?
Calipers are fine (just rechecked them), new front hoses and slave cylinders. Not a bleeding issue - I know the difference between a springy air pedal and and fluid being forced through a tight gap in the manner of hydraulic damping - which is how the pedal feels. ABS operates as it should when pushed. (Don't have scan tool to bleed ABS unit but have had it operating and no difference. Anyway, ABS is out of the loop when pedal is sinking and not bleed issue). None of the MCs when removed showed any signs of external leakage, no other external leaks and fluid level never drops.
Apologies for then length of this post - but as you can appreciate, I need to get on top of this. Throwing a new ($100) MC at it every few hundred miles isn't a viable option. I need at least to be able to rebuild the MCs I have until a permanent solution (if better seals aren't the answer) is found.
Or are the MCs bad?
