Flushing the brake system

[Old Guy]

My go-to solution for brake system flushing is usually a pressure bleeder. Unfortunately, the pressure bleeder that I have used on other vehicles doesn't have a screw on adapter that fits the NSX (has to be the worlds largest diameter MC reservoir). As other Primers have reported, it seems impossible to get the flat plate clamp over the top with a chain around the bottom style pressure bleeders to seal on the MC top, so doing this single handed I elected to use my Mity Vac tool.

Having helped my son do a brake flush on his RSX with the Mity Vac, I knew that the Mity Vac process was a bit slow compared to a pressure bleeder. Well on my 2000 NSX slow was not the appropriate description. Glacial is more like it. I probably had to pump for about 25+ minutes on each caliper to extract about 250+ ml of fluid from each caliper port. Has anybody else used a Mity Vac to flush their brake system? If so, is there some magic trick that I omitted that would speed this up or is this just the way it is?

For what it is worth, my last brake fluid flush was 4 years ago (I had the dealership do it). The fluid that was coming out of the calipers this time was pretty much indistinguishable from the Honda DOT 3 fluid that I was adding into the MC with no sediment at all. I don't know whether that speaks to the Honda fluid, the brake system or my driving; however, based on what I saw, for a non tracked vehicle I would be pretty comfortable extending the flush interval out to 5 years.

The up-side is that I had a really good right fore-arm workout. The down-side is that its probably going to be about a day before I can sign my name and have it legible.

 

[jwmelvin]

I use one of the Venturi vacuum pumps so I can’t speak to the pumping required but, with my tool, the brake fluid flies through the system at a rapid rate.

 

[goldNSX]

Pressure bleeder: hard to seal at the top, loss of pressure, mess.
Vaccum bleeder (very cheap one): great! BUT if you don't use a sealant around the screw threads you'll loose pressure, just suck the air around the bleeder screw (kind of shortcut) and pump your hands off. I've coated the bleeder screws with the sealant Speedbleeder uses. With the sealant it's maybe half as fast as with pressure bleeding. The more fluid you extract to lower the pressure goes, so you have to pump it up as soon as the canister is 1/2 to keep the fluid speed at a high rate. An electric vacuum pump would be on my wishlist for the next time.

Not having the right tools is no reason to extend the interval to 5 years. :wink: I do it every spring including the clutch system which is quite dirty around the slave after only one year.

 

[Old Guy]

My Mity Vac easily pulled a vacuum of 400 - 500 mm (assuming the gauge is correct). The theoretical max is around 750 mm (less if you live way above sea level) so its not obvious to me that an external vacuum pump capable of pulling a better vacuum would have been a whole lot faster. It certainly would have been a lot easier. [MENTION=10201]goldNSX[/MENTION] 's observation about sealant on the threads is interesting because during the bleed process it is apparent that air is being admitted through the bleed screw. Do you think this is just a regular pipe thread sealant or something special. I could see that sealing the threads might be the ticket to getting a faster vacuum bleed.

In addition to a proper screw on bleeder attachment that I have used on other cars, I tried one of the flat top adapters like the Motive (mine was a different brand and different color but effectively the same) described here:

http://www.nsxprime.com/forum/showthread.php/159552-DIY-NSX-Brake-bleed-using-Motive-power-bleeder

Just as other people had described, regardless of what I experimented with for a sealing gasket, I could never get it to seal. However, in the final post in the above thread [MENTION=29720]jizheng[/MENTION] modified the cap to use two hold down chains, perhaps distributing the clamping force around the top of the reservoir better. I may retrieve that flat adapter from the garbage bag where it went yesterday and modify it the same way for the next time I try this.

My observation about extending the flush interval was not based upon the difficulty of doing the flush. It was based upon the fact that what was coming out of the calipers looked exactly like the fresh stuff that I was pouring in to the reservoir. I agree that appearance is not a guarantee about degradation that may be occurring in the boiling point. If I was going to the track I would be using short change intervals.

 

[goldNSX]

[MENTION=10201]goldNSX[/MENTION] 's observation about sealant on the threads is interesting because during the bleed process it is apparent that air is being admitted through the bleed screw. Do you think this is just a regular pipe thread sealant or something special. I could see that sealing the threads might be the ticket to getting a faster vacuum bleed.

The sealant is crucial when you use a vaccum bleeder tool. Most suppliers won't tell you about this, so most tools end up in the waste bucket. Try teflon, Hondabond or a light Locktite or maybe the best of all of them: the original Speedbleeder sealant. http://store-speedbleeder-com.3dcartstores.com/-Accessories_c_1.html The trick is that the sealant is still working after 5 or 10 you've opened the valve.

My observation about extending the flush interval was not based upon the difficulty of doing the flush. It was based upon the fact that what was coming out of the calipers looked exactly like the fresh stuff that I was pouring in to the reservoir. I agree that appearance is not a guarantee about degradation that may be occurring in the boiling point. If I was going to the track I would be using short change intervals.

I'm more concerned about water and the seals. The boiling point will be maxed out anyway/too...

 

[jwmelvin]

I always smear some grease around the base of the bleeder screw when vacuum bleeding. It’s a critical part of the process and is effective to stop the leak, though you generally have to manipulate the grease after unscrewing the bleeder to get it to seal.

 

[dirtbag]

I haven't had extreme difficulties using the generic plate with pressure bleeding. What I did discover is if you lubricate the rubber gasket, it seals much easier. The chains are kind of a pain to loop properly.

Next time I go through the bleed process, I'll create a 3d printed cap, or modified aftermarket cap for our NSX's for free download or hardware purchase if a one hasn't already been developed by then. That seems like a fairly simple project.

 

[Old Guy]

Next time I go through the bleed process, I'll create a 3d printed cap, or modified aftermarket cap for our NSX's for free download or hardware purchase if a one hasn't already been developed by then. That seems like a fairly simple project.

That would be nice.

I had thought about getting a reservoir cap from a pick and pull and fitting it with an adapter to accept an air line. NSXs in pick and pull yards are non existent; but, I figured that there must be other Hondas that shared the same reservoir. There were; but, not many. As far as I could determine, the only Hondas that shared that reservoir were some Accords in the late 80s and some Preludes in the early 90s. These are also equally rare as they are old enough that they have all probably been crushed and turned into pipe for the Keystone XL pipeline.

If push comes to shove new caps are still available from Honda for about $40.

 

[Old Guy]

So a little bit of success on the reservoir cap front. Parts cross matching suggested that 1999 to around 2004 Odysseys had the same MC reservoir cap and as it turned out, our pick and pull had a selection of Odysseys to examine. I went out to the pick and pull this morning; but, before I ever made it over to the Odysseys in the yard I came across a selection of 90s Integras and all of those that still had their MCs in place had the same cap as the NSX. One of them also yielded a matching clutch reservoir cap. So now I am potentially set up to do a pressure bleed on both the brakes and clutch on the NSX. I also stumbled across a Pilot and a really picked over RSX so I am also potentially set up to pressure bleed our daily driver Pilot and my son's RSX. I never did make it over to the line up of Odysseys to confirm whether they also use the same cap as the NSX.

Examination of the caps indicates that the caps do not seal on the top surface of the reservoir. They have an insert under the cap which fits down into the reservoir and sealing is accomplished by an O ring around the periphery of the insert which presses against the inside of the reservoir. Perhaps explains why the universal fit bleeder adapters work so poorly on the Honda reservoirs. This arrangement may make 3D printing an adapter cap significantly more complicated.

Modifying the caps to work with a pressure bleeder is not a slam dunk. The caps are vented to atmosphere between the inside insert and the grey plastic cover that is visible. So the grey plastic cover does not form an air tight seal on the reservoir. This is going to require the use of some sealant between the insert and the cover to make an air tight arrangement for pressure bleeding. The Pilot is up next for the brake flush so we will see how the cap modification works out.

 

[nsxspdfreak]

This is what I use and it works great, but you do need a high volume compressor. The feed bottle rests on top of the reservoir and will automatically keep the reservoir full as fluid is sucked out (as long as don't let the bottle run dry). https://www.amazon.com/8milelake-Pn...9101456&sr=1-12&keywords=vacuum+brake+bleeder