Alloy Brake Calipers & Bleed Nipple Problems.

Retrogamer

I know this is probably best on a dedicated motoring forum but as we have a few active members here with lots of experience i thought i'd ask here first.

I went to replace all the brake fluid on my Mk4 Ibiza recently as i found out it hasn't been changed in the last 8 years and was a horrible blackish colour

The front calipers are steel and the rear ones are alloy.
When i was loosening the bleed nipples on the rear they were extremely tight. I'd cleaned them up and used a penetrating oil to loosen them a bit
My old man had warned me about alloy calipers & bleed nipples and i can see why.

I managed to strip the threads of one caliper whilst loosening the bleed nipple. I'm more used to things stripping when being tightened but not loosened.

So i've ordered a new caliper to fit but wanted to know...


Did it strip because it had been untouched for 8 years, or is this a common thing with alloy calipers regardless of how often the bleed nipple is cracked loose?

I've noticed that you can buy stainless steel / titanium bleed nipples online. Someone mentioned steel and alloy aren't the best combination for things exposed to the weather as they "fuse" together. Would stainless steel or titanium be better?
I want to keep the car the next 4-5 years so i'll be doing the fluid on this again at some point

Thanks for any / all advice.

colino

All dissimilar metals oxidise or corrode when placed together with the handy addition of our wet weather. Ironically a mild steel caliper with a mild steel brake nipple would give you less problems. As you go up the metal rankings the problem becomes less acute, but if they are not the same material, you will still get a galvanic reaction and corrosion will eventually occur.
I hope the new caliper was cheap enough if not, despite the, "think of the children brigade" I would have helicoiled it.

Retrogamer

I didn't have the kit to helicoil it myself and was a little pushed for time.

Would you say the problem with the caliper pulling out the threads is less likely to happen if i replaced the bleed nipples with stainless or titanium as opposed to the oem steel ones? Just won't want to have the same issue in another two years

colino

I would just replace them with standard nipples, and before you final fit, make sure they are a good fit by running them in and out completely a few times to make sure you are not compounding the problem with poor machining. I wouldn't go to the extreme of fitting expensive replacements that may or may not benefit you down the line.
Incidentally, when you crack a stubborn connection like this anywhere on the car, undo them a quarter of a turn, retighten, undo a half turn, turn them back a quarter, undo a half turn and continue until it is fully free.
Hopefully you've just been unlucky this time and putting a little rubber bonnet on the nipple and slathering the rest of the visible nipple will make it easier next time.

AdrianC

It's down to time. There's no reason why nipples would seize in two years, which is the correct interval to be changing brake fluid.

If you're worried about it, just put a little smear of copaslip on the thread of the nipple (not the pointed end, just the thread) before fitting it.

facade

Many motorcyclists have found who believe what they read in adverts, and change all the engine bolts on their 'bikes, screwing stainless steel into alloy is a sure fire way of making sure that you can never undo it again. :eek:

Fit the standard plated steel nipples, put a slight smear of aluminium anti-seize on the threads.

(Be warned that the carrier for anti-seize may react with the rubber in your brake cylinders and cause you to lose all the brakes when you are facing a line of basket of kitten wielding Nuns holding the hands of orphaned children. So only a tiny smear on the thread )

Retrogamer

Thanks everyone for the input.
All my previous cars had drums at the back and steel calipers up front so never experienced this before

The brand new caliper came with a new nipple so that's all fine an the other nipple on the near side caliper is still ok. Both were mega tight to loosen and i did loosen / re-tighten both whilst adding plus gas (penetrating oil) in now and then to help but still no joy.

On the plus side, it had to be done. The fluid was black and particles of rust inside in so even though the car had "FSH" you can tell the brake fluid has never been changed.

JustinR1979

There is someone on here running round with 16 year old brake fluid, wonder how his nipples are....

arcon5

Damn, that beats my 13 year old brake fluid :mad:

I'm sure you buy buy re-threading tools for less than a tenner

londonTiger

if you have a workship you will need to drill a bigger hole and use a tap & die set to retread it and use a bigger bolt. Otherwise buy a new caliper.

Master_Blaster

londonTiger wrote: »

if you have a workship you will need to drill a bigger hole and use a tap & die set to retread it and use a bigger bolt. Otherwise buy a new caliper.

Londontiger your comedy posts alway make me :rotfl:.:T