'98 V70 Brake Reservoir Cap Leaking

[bmdubya1198]

Well, I bled my brakes about 3 times yesterday alone after replacing my master cylinder, along with 5-6 other times within the past couple weeks, and the brakes finally feel a bit like they're actually doing something and not pressing sponges against my rotors. Maybe the brake pedal is supposed to feel soft in this car, I don't know. The brakes haven't been right in this car since I bought it.
Anyway, the brakes had gotten consistently worse since I replaced the rotors and pads a month or two ago, and recently to the point where they're terrifying. My brake pedal was going almost to the floor and the brakes felt like sponges. I figured there was just air trapped in the system, but realized after a few bleeds that can't be the case. After reading around on here, I decided to pick up a master cylinder yesterday, and after bleeding a couple times, like I said, they feel a little better. But now I'm afraid there is air getting in from the reservoir cap.
I replaced the cap last week for the same reason, but now this one is leaking. Am I doing something wrong? Like tightening it too much possibly? Anyway, I got this cap from the junkyard after I looked it up on Lisle and discovered it's $60!!!!! That's nuts for a brake reservoir cap.
Does anyone know if there's some kind of fix to the seal maybe? I don't want to spend that kind of money on a reservoir cap when I have to replace my parking brake shoes (they don't work at all, but that's another thread for another day...), front brake lines (they're just a little worn at the ends, I don't think they are leaking), and a bunch of other stuff. Just to add, I'm not losing any brake fluid anywhere else. The level stays at max, the only fluid leaking is on the cap.

[abscate]

Air from the cap won't affect the braking, so if you are feeling funkiness you have air somewhere else. How full is the reservoir? It should only be full up to the MAX line, not topped off to the top of the reservoir. If you do that, when you stuff the float back in, it will overflow!

Are all of your calipers sliding freely? Up here in salt country, we have to wire brush and grease our caliper slides on a brake job or else the stick and will give that weird feeling

[bmdubya1198]

Air from the cap won't affect the braking, so if you are feeling funkiness you have air somewhere else. How full is the reservoir? It should only be full up to the MAX line, not topped off to the top of the reservoir. If you do that, when you stuff the float back in, it will overflow!

Are all of your calipers sliding freely? Up here in salt country, we have to wire brush and grease our caliper slides on a brake job or else the stick and will give that weird feeling

Yeah, I thought so, but I figured it was a leak, a broken seal in a sealed system. It was something to look into.
The reservoir is filled to the MAX line. I'll admit, it's a little hard to see since I have such nice clean fluid in there now, but I don't think it's over MAX. It's not so full that the float is causing it to overflow.
As far as I know, the calipers are sliding freely. However, when I'm driving I occasionally get a rattling/screeching sound from the front brakes. It's been there since I replaced the brakes, and at first I figured they were just setting, but I don't think that's the case. It's still driving me nuts after about 2 months. FWIW, I did notice after a very short drive (<2 miles) that there was probably 1/2" of rust still on the front left rotor (it rained the previous night). I wasn't doing a lot of braking, but it was noticeable. The front right was clean of rust. Don't know if this is normal or not after 1,000 miles on new brakes, but the machining marks are still there.
When I did the brakes, though I did make sure to grease the guide pins and all contact surfaces of the pads with some disk brake lube.

[abscate]

Uh oh, thats not good. Watch it closely - if it does not polish off, it means the piston is sticking in the caliper, or the pad is hanging up in the slide. That will also give you a bad pedal feel.

[bmdubya1198]

Uh oh, thats not good. Watch it closely - if it does not polish off, it means the piston is sticking in the caliper, or the pad is hanging up in the slide. That will also give you a bad pedal feel.

Well as of the last time I looked, it was clean. I just washed my car, so the rotors are probably rusty now, so I'll check them in a little bit as I'm about to go to the store.
I plan to replace the seals in the front calipers anyway, so hopefully they're just starting to go out and it's not a huge problem yet. I'll keep an eye on it!

[abscate]

Do you have >200 miles on the new pads yet? They take a while to bed in the rotors.

And, avoid hard braking during that time. (Thats always on the brake pad box, but it is a really stupid thing to say, isnt it?)

[bmdubya1198]

Yes, I have about 1,500 miles on the pads and rotors. I did a bed-in process that I saw online probably a day or two after putting them in which involved stopping from 30 once or twice, then 45, then 30, then a 2 hour cool down time.
Just checked the rotors after my Harbor Freight run and they are all 100% clean. They were all rusted before I left.

[theWIFES_S70]

hey bmdubya1198, did you ever get around to fixing the leak around your master cylinder cap?

I can't believe the cap is $60...

[bmdubya1198]

hey bmdubya1198, did you ever get around to fixing the leak around your master cylinder cap?

I can't believe the cap is $60...

It seemed to stop for a while, but I just noticed yesterday it was wet again. I just can't justify spending $60 on a cap though, it's ridiculous.
I had one I got at the junkyard, but that one did the same thing. I thought maybe I hadn't clicked the two parts together (sensor connector and threaded cap part) but that's not the problem now.

[theWIFES_S70]

Yeah, I'm in the same boat, too. I wonder if it's just the rubber washer that has torn somehow because of opening and closing it... There's got to be a way to DIY this. Of course, without spending the $60. (Though, it would be guaranteed for life, right?)