Brakes Brake fluid reservoir replacement

[91AOD5.0LX]

1991 LX 5.0:
Has anyone ever replaced just the reservoir on the factory master cylinder? If so can you explain how it’s done if not to complicated please.
Wondering if it’s easy enough and not to risky otherwise I will disregard. I’m just looking to get a nice clean reservoir that I can actually see the fluid in. Any info is appreciated.
Assume 1987-1993 is the same or similar if anyone has done this.

 

[evintho]

I replaced the reservoir a few years ago. IIRC, it just popped out and the new one snapped in. I think there're O-rings that seal it in. Memory is kinda faded!

 

[91AOD5.0LX]

I replaced the reservoir a few years ago. IIRC, it just popped out and the new one snapped in. I think there're O-rings that seal it in. Memory is kinda faded!

Ok that sounds easy enough. Thanks for that input!

 

[Mustang5L5]

I did one a long time ago, but it is that easy. If you are doing it on the car, wrap the MC in rags and put some underneath as fluid will splash when you pull that guy off.

 

[91AOD5.0LX]

I did one a long time ago, but it is that easy. If you are doing it on the car, wrap the MC in rags and put some underneath as fluid will splash when you pull that guy off.

Ok sounds easy. I bought an NOS reservoir and are chopping at the big to install but can’t find any videos or info online so hesitating to do so but it sounds like it may be easy. I don’t want to replace the entire master with a Chinese part when mine works fine. Just needs a clean belittle because of my OCD. Lol
Will wrap it up good and go slow. Can’t find the grommets/seals anywhere. They dont come with the reservoir so I wil wait until I hopefully find them. Just doing my research now in advance.
Thanks for your info!
PS: this may be a stupid question also but after the reservoir is installed and fluid filled does anything else have to be done such as bleeding that your aware of?

 

[Mustang5L5]

I've never done one on the car, so I don't know, but the one I did was on a bench and I did bench bleed the MC afterwards.

Theoretically if you introduce air into the MC, it's very difficult to get it to purge out because of the angle of the MC. It tends to trap itself at the highest point shown here in red

I think if i was doing this on my car, i'd pull the MC off and just swap the reservoir and bench bleed it. If you are going to go that far, why not just replace the MC completely? Obviously that's your decison


The reserviours typically come with seals. So if yours are missing you might need to take them from your original or maybe buy a parts store unit and swap them. As with the case with all parts for the fox bodies, slim pickings on who makes stuff these days. Looks like the Cardone 1R4005 is the only unit available these days.

https://www.summitracing.com/parts/aaz-1r4005

 

[91AOD5.0LX]

I've never done one on the car, so I don't know, but the one I did was on a bench and I did bench bleed the MC afterwards.

Theoretically if you introduce air into the MC, it's very difficult to get it to purge out because of the angle of the MC. It tends to trap itself at the highest point shown here in red

I think if i was doing this on my car, i'd pull the MC off and just swap the reservoir and bench bleed it. If you are going to go that far, why not just replace the MC completely? Obviously that's your decison


The reserviours typically come with seals. So if yours are missing you might need to take them from your original or maybe buy a parts store unit and swap them. As with the case with all parts for the fox bodies, slim pickings on who makes stuff these days. Looks like the Cardone 1R4005 is the only unit available these days.

https://www.summitracing.com/parts/aaz-1r4005

Thanks for this diagram. I may just leave it alone but if I get the itch then will consider bench bleeding the MC off the car as you suggested. Something tells me just to leave it alone. Lots of trouble maybe just to change a reservoir. The more research I do the better my decision will be made. I don’t want to swap the entire MC because it’s working fine and the only replacements would be made overseas. As for the seals, I lf it comes down to that then I will swap with a store brand if they fit otherwise try and retain the originals. I may just leave it alone the more I’m thinking. Lol

 

[General karthief]

You could take a turkey baster and remove as much fluid as you can, changing the fluid when it starts to get dark is a good idea anyway but I think I 'd leave it.

 

[90sickfox]

The reservoirs can be a bit of a pain popping off. I get all the fluid out with a mighty vac and pry it off with a small pry bar or a couple screw drivers. Sometimes it'll feel like the plastic is going to crack but I've never cracked one.

 

[7991LXnSHO]

How long has it been since you changed the brake fluid? As it attracts water, I would not be likely to just swap the top tank.

 

[91AOD5.0LX]

How long has it been since you changed the brake fluid? As it attracts water, I would not be likely to just swap the top tank.

Changed it 1 year ago

 

[7991LXnSHO]

Changed it 1 year ago

Well, that complicates the OCD. Just keep the fluid off the paint.

 

[91AOD5.0LX]

Well, that complicates the OCD. Just keep the fluid off the paint.

It sure does! Lol
Will wrap up underneath to prevent spillage

 

[evintho]

Take pics and let us know how it went. That'll help the next guy who has to do it.

 

[91AOD5.0LX]

Take pics and let us know how it went. That'll help the next guy who has to do it.

Will do

 

[91AOD5.0LX]

Nothing is ever straight forward!
Ok, so does anyone know why the attached photos of brake fluid reservoirs are different but both are for a 1991 mustang 5.0 (and other years).
Both have the same part number but as you can see, the original one is slanted, raised but the other (replacement) is flat, not raised. The 2 nipples are different sizes also.
My NOS part was delivered today and I noticed it’s the slanted one but mine in the car is the flat one. Mine is stock and hasn’t been replaced. Not sure why or if this will work? The photos attached are just for reference. The NOS part I bought is the same part number as the one in the photo (original) and the replacement one in the other photo corresponds with the same original part number but looks different.
Any info is appreciated if anyone knows why these are different but if they would fit.

 

[Mustang5L5]

The original MC on my ‘88 looks like your original.

I want to say that slanted/tilted variety is what came on my 93 Cobra MC and the 94-95 SN95 MC. Let me see if I can find a pic.

 

[Mustang5L5]

Yup. The tilted variety is 93 cobra and 94-95 GT and Cobra MC

It’s entirely possible the tilted variety superceeds the older style. I don’t have both in hand to do some test fit so no idea if the “tilt” version is backwards compatible.

 

[91AOD5.0LX]

The original MC on my ‘88 looks like your original.

I want to say that slanted/tilted variety is what came on my 93 Cobra MC and the 94-95 SN95 MC. Let me see if I can find a pic.

Ok thanks! I appreciate that!
The part number on the slanted calls for my car and the replacement reservoir corresponds with the same part number but are different.
Im thinking the slanted is wrong and won’t work with my car.

 

[91AOD5.0LX]

Yup. The tilted variety is 93 cobra and 94-95 GT and Cobra MC

It’s entirely possible the tilted variety superceeds the older style. I don’t have both in hand to do some test fit so no idea if the “tilt” version is backwards compatible.

I’d hate to pull it off and then find out it doesn’t fit. Horrible! I’m thinking it won’t because the NOS has 2 small nipples whereas the replacement has 1 big and 1 small. That slanted likely won’t fit into the original grommets.