1st gen VR4 brake conversion big issues :(

[TUFFTR]

1 Master cylinder maybe? 2 Have you asked this question on AMC? 3 I'm sure there have been others fitting GTO brakes to a Magna? 4 After going for a drive when you look at the caliper is the pad floating free from the rotor or does it look normal? 5 I assume you bled them in the correct sequence? rear left, rear right, front left, front right? 6 Have you inspected your brake lines? 7 no swelling brake lines that might be expanding under pressure?

1) Well could be, but my brakes worked totally fine before the conversion!
2) Sorta banned on there for a while, Plus no-one really knows anything on that website anyway
3) Actually AFAIK I'm the first!
4) It looks normal to me, but I will have the car on jackstands tomorrow and while it running get someone to press the brakes while I look at the caliper
5) Yes, always bleed in that order. Except when the new brakes when on the front I only bled the front. Rears were only done 500km's ago so no need to do all 4 again.
6) Again yes, My lines AFAIK are in good order. No signs of visual wear front or rear.
7) I doubt it, although anything is possible. if it was swelling under pressure, it wouldnt explain the master cylinder puking the fluid out.

Am I right in thinking I either need a bigger master cyl or one - or both - of these calipers need to be taken apart and inspected?

[tabasco122]

you generally need a larger MC when upgrading to more pots. It requires more fluid to get the same amount of pressure as your old brakes, so you old MC generally wont be up to the task. I dont think that would cause the fluid to come out the MC though, it would just give you bad brake performance.

[TUFFTR]

Understood. So It's strange how I have both symptoms. May start looking at a rebuild kit for these calipers. Knew I should of done this when i got them. ARGH.

[tabasco122]

i dont have any experience with 3s brakes, but that is how it goes when upgrading from the 4 (total) pot 240sx calipers to the 12pot 300zx system (front and rear). it sucks if you upgrade the brakes without doing the MC. you can usually get away with just the front brakes, but if you upgrade the rears too you need a larger MC

[TUFFTR]

Steve, Why do I need to bleed the rear ones if I only disconnected the hoses from the front and re-connected the new hoses right away? Would this in anyway cause what is happening?

[GTOJOE]

It's always a good idea to bleed all of them after working on the braking system. Better to be safe than sorry.

[TUFFTR]

I'll give that go on the weekend then. No big issues there, 5 minute job. I'll put it up on the stands tomorrow and see whats going on when I stomp on em. I would of thought the standard master cyl would of had enough force to push them. Who knows maybe both calipers do need a rebuild?

[GTOJOE]

I was more refering to what the pads look like after a drive. I was thinking that maybe the pads are being pushed back which would push the pistons back and cause the fluid leakage you are having issues with. However I'm sure you would feel it if there was warped rotors or movement etc.

[TUFFTR]

Definitely no movement. Rotors have just have been machined so yeah....HmMMMMMmMMmMMM

[Rocket]

If it was one brake I would say a bad rubber house going to the caliper. If it is all of then and you are pushing fluid out the mc then it almost has top be a plugged line. air in the system would give a soft peddle but shouldn't cause overflow from the mc. Bleed the rears and see how that goes.

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