Gravity feed bleeding?

[davidf]

When I installed my front BBK way back I decided since I was by myself I would try the gravity feed type bleeding. I must say it worked flawlessly. As it dripped in the pans, I kept watch and kept the resorvoir full until it was crystal clear. I had instant brakes when I hit the pedal. Now heres my delima!! My clutch master and slave have both been replaced before and it's time to flush. Can the system be gravity bled as the brakes were? Things are working flawlessly but I need to know it's been flushed. Thank's for any constructive input.:smile:

 

[grybrd]

I am about to do my brakes and appreciate the confirmation that gravity bleeding works as well on the NSX as it does on boat trailers (with which I am quite familiar). We always used that system when rebuilding trailer brakes.

 

[bonds]

When I installed my front BBK way back I decided since I was by myself I would try the gravity feed type bleeding. I must say it worked flawlessly. As it dripped in the pans, I kept watch and kept the resorvoir full until it was crystal clear. I had instant brakes when I hit the pedal. Now heres my delima!! My clutch master and slave have both been replaced before and it's time to flush. Can the system be gravity bled as the brakes were? Things are working flawlessly but I need to know it's been flushed. Thank's for any constructive input.:smile:

Best way to bleed the clutch is have a friend pump the clutch, than hold, as you pop the 8mm bleed screw, use a full bottle of dot 3 fluid or whatever you like, you may need a bottle and a half. After you have bleed through a full bottle of fluid through the clutch master cyl. Start the car than in neutral, than engage the clutch, put in first gear than fan the clutch a bit, it should grab about 2.5-3 inch from the floor. the clutch may feel a bit strange at first but after you drive couple of miles it will feel normal, if not than you have some air in the clutch line and you may have to bleed again.

 

[davidf]

Best way to bleed the clutch is have a friend pump the clutch, than hold, as you pop the 8mm bleed screw, use a full bottle of dot 3 fluid or whatever you like, you may need a bottle and a half. After you have bleed through a full bottle of fluid through the clutch master cyl. Start the car than in neutral, than engage the clutch, put in first gear than fan the clutch a bit, it should grab about 2.5-3 inch from the floor. the clutch may feel a bit strange at first but after you drive couple of miles it will feel normal, if not than you have some air in the clutch line and you may have to bleed again.

Ok, worst case senerio, I can't get help pumping. Will gravity work? The reason I ask, with gravity, no air gets into the system.

 

[goldNSX]

I did it with the gravity method and it works even better than on the brakes.

 

[ATERPAK]

Well think about it a little. What happens when a brake hose cracks with no brake pressure and starts leaking? Isn't that because gravity is forcing the fluid out. As long as the reservoirs are higher than the items you wish to bleed, this should work although it will be slow. This can only work if the master cylinders are above the items you wish to bleed. Some race cars, such as FM' or FF's have their master cylinders below the brake calipers or clutch slave cylinder. Gravity feed would not work for them. If you can afford $50 and have an air compressor, then go for one of the vacuum bleeders out there. It works great and the whole thing will go a lot faster. This is especially handy if you track the car a lot and have to bleed the brakes often.

Al

 

[Swift]

WARNING:

ASE tech so please be listen before doing your own brakes to some advice.

I once replaced rear wheel cylinders on a jaguar. I pinched off the hoses(to make less mess) and replaced them. While i was taking care of other things i let gravity bleed(went to min. line then on master and closed bleed screws). I took for a test drive and couldn't be happier. Nice firm peddle, no fading, nothing to indicate a problem. A few hours later a coworker went to move the car and it had NO pedal. So yeah scratch your head on that one for a while


So if you are alone and want to save money. Yes, gravity bleed to "flush" the system HOWEVER ,please at the very least, put a short piece of wood or anything up against brake pedal(to establish pressure), crack bleed screw, then close, then take the object of choice of brake pedal. do that about 3 times and you are set!

For bleeding clutches it is essential you do it slow like this. Most techs have another guy hop in real quick , stab at the brake pedal real fast three times, crack bleeder and repeat. This will not work on a clutch. You have to do SLOW pumps. It only takes a few pumps once you have let it gravity bleed to know you have a nice firm clutch pedal.

good luck and be safe. your steering can fail and you have brakes, your gas gets stuck open you have brakes, your tranny fails you have brakes, your brakes fail..............you have prayers.

Ps- if you replace master cylinder there is a cheap DIY kit at orielly's that you use to bench bleed it before installing

 

[ATERPAK]

If you were working on an early Jag., then can I ask what type of brake fluid did you use? Early British cars used a different brake fluid than American cars. Our fluid is glycol based and theirs were ether based fluids. Now what does that really mean. Primarily when you change the brake fluid of a British vehicle you better use the correct type of brake fluid or your asking for some major problems. What happens is the glycol based fluids start eating into the seals in the master cylinder, brake cylinders and any place else where any seals come into contact with the fluid for the British cars. This causes any pressure build up in the system to push right pass the seals and thus little to no brake pressure. This also means you will have to replace all the seals and re-bleed the entire system with the correct type of fluid for the system to work properly again. American systems not only use a different fluid but their seals are more synthetic than the British of the period which primarily used a more natural rubber type of seal. Today everyone uses the same basic DOT standard and seals are all compatible as long as you stay away from DOT 5.1 which should only be used if the system is completely new or you want to use it for a classic restoration and don't want water absorbing into the fluid over a long period of time and non-use of the cars brakes.


Al

 

[grybrd]

Great comment on the differences in brake fluid.
I remember my 71 TR6 where I had to rebuild the brakes top to bottom after adding the incorrect fluid and seeing the reservoir turn brackish. I disolved the seals but caught it before I drove the car that way.

 

[davidf]

Someone recommend me some excellent brake fluid. I have Prestone DOT 3 synthetic but want the best for this application. Thanks.

 

[BrakeExpert]

Several track racing buddies of mine including an ITR driver use Valvoline. Its a DOT4, its full synthetic, and its cheap, like 6 bucks for a quart and its a DOT4. You can get it at Autozone.

 

[davidf]

Thanks, off to the Zone.:smile:

 

[pgilliam1]

I have had better luck gravity bleeding the clutch and brakes on my NSX ( I tap on the caliper with a rubber hammer to dislodge any bubbles after I open the bleeders). I use Valvoline synthetic and have had no problems on the track or the street. Happy Motoring!

 

[shawn110975]

I cant find where to buy DOT 4 about a month ago I tried to buy some went to 3 different stores and they didnt carry it,, asked them where i might find someone that stocks it they had no clue!!

 

[pgilliam1]

I cant find where to buy DOT 4 about a month ago I tried to buy some went to 3 different stores and they didnt carry it,, asked them where i might find someone that stocks it they had no clue!!

Valvoline Synthetic is DOT 4 and can be found at any Auto Zone.