wallifishrmn

Rebuilt the original brake calipers about 7-8 years ago and switched to dot 5. No problems. Now the left rear has started to leak.

Had a mechanic friend check it out to make sure I didn't do anything wrong when I rbuilt them (all 4 calipers). He comments are as follows--"As far as the caliper goes, no you didn't screw up. Took it a part and found all the seals to be installed correctly. I resealed it and bleed the system. Drove the car and then let it sit overnight to inspect. It's still leaking. At this point with no visual issues. Just an FYI all the calipers I buy have a sticker on the box that states that if DOT 5 is used it voids the warranty. I would suggest another caliper and installing DOT 3."

I don't want to replace the original numbered calipers. Also don't want to replace DOT 5. Any thoughts or suggestions greatly appreciated.

Thanks as always for all your help.
Wallifishrmn

540 vette

Why do you want DOT 5.

stingr69

There is not much else than can go wrong unless the bores are trash and need to be sleeved with SS. Might need to replace the pistons if they are worn.

wallifishrmn

DOT 5 is NOT hydroscopic--doesn't pull in water; is more stable over a range of temperatures; does NOT take the paint off like DOT 3 if you get it on the car.

Fredtoo

With DOT 5, and moisture that does get in, stays as water droplets, as opposed to being in solution with DOT 3.
This can cause rust in low spots in the system

The other issue with DOT 5 is that it is harder to bleed. any air bubble that do get in, tend to stay as little tiny bubbles.

I would suggest looking at a DOT 4 fluid, it is less hygroscopic that DOT 3 and does not require flushing as often.

resdoggie

Find out why DOT 5 is not compatible with your calipers. Only thing I can think of is the seals. If so, buy compatible seals.

wallifishrmn

The other 4 brake calipers (both front) and one rear are fine. I didn't know some seals weren't compatible with DOT 5--is that true???

v2racing

I have been using DOT5 since the mid 70's. I have used it in cars and motorcycles on the street, drag racing, land speed racing, and road racing. I have never had one issue caused by DOT5. It doesn't attack rubber, so I don't know why a warranty would be voided by it. It may be that if you aren't careful pouring the fluid in or are too aggressive pumping the brake pedal during bleeding, you can make air bubbles in it that are difficult to get out. Customers tend to blame the last part bought for problems, so maybe that has something to do with it.

If care is taken to have system clean and dry, and you take your time pouring the fluid and bleeding it, you shouldn't ever have problems with it. Gravity bleeding, while slow, works well with DOT5 as you do not introduce air bubbles to the fluid.

If you have a caliper leaking, there is something wrong with the caliper, not the fluid.

Mike

resdoggie

You quoted a statement from your mechanic about not using DOT 5 which voids warranty. Maybe the manufacturer is concerned with air bubbles in DOT 5 if not properly filled/bled. I doubt it has to do with the seals myself but the 'sticker' says not to use it for a reason or your mechanic got it wrong. Its probably leaking from wear and tear as already suggested.

joewill

so your mechanic took it all apart to the point of examining the seals?

just as easy then to spend the money and put new seals in it for a very minor increment in cost? new seals, wipe the bores with Emory cloth.. good as new.

seals sometimes leak for microscopic reasons.. rebuild them again, 8 years is about all you are gonna get out of them anyway unless you are a daily driver to keep them exercised.

yes use dot 3

wallifishrmn

I rebuilt them myself about 8 years ago but don't have the car right now. My friend (a mechanic) looked and notice a leak. Here's what he did:I replaced all the seals and dust boots. Still seeping. The repair is to flush the system of DOT 5 and/or replace the caliper. I saw nothing wrong with your rebuild. There is either a caliper issue or the DOT 5 is the issue. As I said before and my caliper boxes come with a stick that states warranty void if you use DOT 5. Can't believe there's something wrong with the caliper????

FINWOLF

Look I don't have a dog in this fight. I have been using dot5 for 20 years no problem. But listen to this guy. but if this is true then why did only one caliper fail.

Mr D.

Put new seals in the leaking caliper, don't over think this.

wallifishrmn

He replaced the seals and it still leaks. All the brake lines and parts were replaced before installing DOT 5. Any suggestions. Could it be the piston??

v2racing

Yes it could be the piston or a flaw in the bore that your mechanic missed.

Mike

Mr D.

Go to O'Rileys and buy a caliper for $50 and install it, take your OEM caliper and send it out for rebuilding. It can be re-sleeved, new pistons, seals Etc.

resdoggie

Or the mechanic?

v2racing

I've seen O'Riley's rebuilds that the bores were shot in. It took several tries to find ones that had SS sleeves in them. Even then they had blasted the calipers and the bores were not protected. I had to run a hone in in them to smooth them back out.


Mike

Duntov

There has been discussions around DOT 5, warranties, and issues. Essentially the DOT5 manufactures self regulate their formulas to comply with the EPA. About 15-20 years ago the fluid is different than what you can generally buy now. If the fluid was bought recently you likely will have issues. With the new fluid the seals expand causing sealing issues and potential operation issues. Corvette Stainless Steel Brakes has info on their site about this. Also talked with Lucas/Luke about it as well. As others have stated, DOT5 is desirable since it doesn’t absorb moisture, high boiling point, stable composition, etc. It does aerate which causes issues in ABS systems.

I purchased some Milspec (Radco) fluid and used it when I had to replace my master cylinder (later booster and master was installed) and so far no issues. Some new Harley-Davidson motorcycles use DOT5, but I have not been able to find out the manufacturer or if conforms to Milspec guideline.

Raybestos states their rubber is compatible with DOT5, but no data on if it’s been tested recently with actual fluid.

car junkie

I have heard oem style lip seals will leak with silicone fluid in cars that see little use, seems true by my experience. Also heard that switching to O ring style pistons and seals will solve this problem. Did the rears a few years ago and am going to do the fronts. Took about 8 years for the first leaks to develop. This is what I'm up to. Yes my calipers were sleeved many years ago. Anyone else go down this road?