Can I replace syntetic brake fluid with Dot 3 fluid if I va***n out the syntetic first? Will there be issues with seals? reason im asking is I believe im having problems with air in the system and im not able to get a good brake pedal. I am thinking of changing to Dot 3 in hopes of not having air and moisture issues.
Have you tried opening the bleeders one at a time and letting them gravity bleed? As it sounds like you already know Dot 5 is very suseptible to air bubbles. Do every thing you can, even while pouring to keep this from happening. If you change to DOT 3 or 4 as mikeco said make sure you flush the system.
You don't have moisture problems with dot 5, you must be sure that you don't induce any kind of bubbles into dot 5 as the previous guy said, its hard to remove and gravity bleeding is the best way with dot 5. I use dot 5 in all my old cars and don't have any problems. I just went to a corvette restoration and repair shop and dot 5 is all they use. good luck
I've had the Dot 5 in Two of my vehicles, the Ranchero for around Eight years, the 46 Truck for over Eighteen with no problems. It is hard to bleed the system with the Dot 5, but worth the results,
Instead of debating the values of each, I'll answer the question. Yes, you can convert, but you must make sure you get all the old fluid out - they don't like each other and can turn things "Gummy". Open all the bleeders and drain the DOT5. Then pump any remaining fluid out. Now put in the DOT 3 and flush the entire system one wheel at a time, i usually push a complete M/C reservoir worth of fluid through each wheel to be sure all the offending fluid is gone. Then bleed as normal. BTW, I like DOT 5
Using DOT 5 in both of our hobby cars. I like the fact that it don't draw moister, don't eat paint, and we've never ran into any kind of problems while bleeding the systems.
So if I keep the Dot 5 in the system, I can try gravity bleeding the cylinders one at a time. you just open the bleeder and let it run making sure the master stays full correct? How do you know when to stop bleeding this way? no need to pump or hold the pedal down? thanks for the info!
There seems to be some misinformation about the Dot 5 & moisture. Unlike the Glycol based Dot 3 & 4, Dot 5 will not absorbe moisture or disperse it which leads to corrosion problems. It was designed for hi temp / racing conditions where the fluid is changed quite often. It is more prone to air problems and is more compressable resulting in a spongy pedal. The only advantage of using it on a street car is that it won't eat paint or plastic. I would stick to your original plan & replace it with Dot 4 for a number of reasons.JMO.
JFYI, synthetic brake fluid refers to, and is technically, DOT 3, 4, and possibly DOT 5.1, all glycol based, and not silicone, which is DOT 5. Bob
Yes you are correct but I was refering to the other comments re: Dot 5. If infact he is just using synthetic & not silicone, then he could mix the 2 but I would still flush the system. I might have mistakenly ***umed (ya know how that goes) like the others that he meant silicone. Sorry for the confusion!
Have Dot 5 synthetic in one of my cars and WILL NEVER DO THAT AGAIN> Lousy pedal, absorbs air and you can never fully get rid of it.
Thanks it is confusing as the OP asks farther down if he could keep the dot 5 in & gravity bleed the system. I hope we haven't confused Ramrod,guess he needs to clarify which he has.Synthetic or Silicone ?
We switched a clients car over from silicone to 3. We drained it, flushed it with alcohol, let it evaporate (left the master cylinder and all bleeders open) over a couple of days, then re-filled and bled the system several times to make certain of no residual silicone or alcohol. This procedure worked very well for us.
I believe that if one checks the tech sheets and advi*****ts on switching fluid one way or the other flushing with alcohol is involved. Note: if there is a vet supply store (farm animal) in the area they usually sell 70% alcohol by the gallon for a lot less then you get the smaller bottles for at the drug store. From what I remember from the workshop that the NAPA brake gurus gave back when Silicone brake fluid came out it is get the fluid level down in the master cylinder and fill and flush well with alcohol and then fill and flush with the new fluid per what Special Ed mentioned before.
Sorry for making this confusing. I have synthetic brake fluid in the system right now. because im either lazy or hope to not have contamination I want to try and get the air out of the system right now. So ill ask again, when gravity bleeding the system do you just leave the bleeder open allowing fluid to drain? if so how long ? do you bleed the brakes after by pumping as well?
i only pump enough to get a little pedal then bleed. don't pump more than you have to then let it sit for a bit and do the next. i use dot 5. the other option is get a screnge and hook a hose to it and blow fluid up through the system to remove any bubbles since they like to rise. don't forget to close bleeders when you finish each wheel cylinder.
Not you fault you said synthetic & we all just took it as Dot 5 silicone which is different. Do you have a spongy pedal,or to much travel? Will it pump up hard and go down while steady holding the pedal? I have never bled a system by gravity bleeding. I know you can crack the cylinders & let it flow but you have to make sure the m/c doesn't run dry. Is this a new system? Did you bench bleed the m/c? Just trying to get an idea of what you have tried/done.
Ok first this is a new system. I installed a new power booster master cylinder and ran all new brake lines. 2 lb and 10 lb checks, proportioning valve for the rear. heres what happened. I was having an issue with sensitive brakes and the fronts locking up almost putting you thru the window. I realized I had not adjusted the rear brakes so I did that and checked again. now the pedal felt better but the front right (p***enger side) was locking up. I pulled the wheel removed the caliper cleaned the rotor and took a piece of emory to the pads as well thinking maybe some dirt , grease was on them. when I did that I compressed the caliper to reinstall the pads. after that when I step in the brakes they go to the floor, now I bleed the wheels again and have what seems like good pedal if I pump and hold the pedal it stays firm. if I release the pedal it will go to the floor and I have to pump it at least once to get pedal again. this is why im thinking I have air. but whats interesting is that before I compresed the caliper the pedal seemed fine other then the locking up. What am I missing??????? I did bleed the master on the truck prior to hooking up the brake lines so I would say yes the master has been bench bleed.
It does sound like air in the system but I would double check the caliper you had off & make sure the pistons are not stuck & are moving the pads. Then I would rebleed the system like Buck Sharp said pump slowly & only enough to get a good pedal. Do the calipers have more then 1 bleeder on them & are they at the top? I'm guessing that the m/c is under the floor & thats why your running the check valves.
So I was able to find a few hours to work on the brakes today. I bleed the brakes several times using a va***n pump. andstill couldnt get a good pedal. I kept thinking that I had an issue with the caliper but did not see any leaks. well I went out and got new calipers for both sides and new pads. installed them and bleed the brakes again. now im getting better pedal! I still want to bleed the brakes again but I want to pump the brakes and bleed them. just to make sure im good to go! Hope this corrects the locking up issues and the poor to no pedal issue. thanks for all the input! Also I have kept the syntetic brake fluid for now.
Thanks for the update. It sounds like you found the problem. Theres something else I thought about but if things are good no point.
It's a no-brainer to me. I've always used dot3. Never had any problems. I hear about people having problems with dot5. Why would I even consider using it?
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