question DOT 4 Synthetic Brake Fluid

[Surveyor]

Can any one advise if there is much of a difference with the military specification and civilian specification for brake fluid?

Penman have advised to use H-542OX-8 for the trailer, I am assuming this would be the same as for the 110 Land Rover, if there is a difference would it pay me to drain the systems of both and use a civilian one.

Still trying to learn what that big lump of metal does under the bonnet

[fv1609]

"H-542OX-8" is a compression of the NATO designation H-542 & the MOD Defence Standard OX-8

 

There is some coverage here:

 

 

http://www.hmvf.co.uk/pdf/POLcompact.pdf

[Surveyor]

"H-542OX-8" is a compression of the NATO designation H-542 & the MOD Defence Standard OX-8

 

There is some coverage here:

 

 

http://www.hmvf.co.uk/pdf/POLcompact.pdf

 

Clive

thanks, my concern is if I go for the brake fluid mentioned in Haynes for the Land Rover and it turns out not to be compatible to what is already in the system as the beast is direct from MoD, I have heard horror stories about having to replace complete brake lines.

[fv1609]

I try to rely on the military spec laid down in the Servicing/Maintenance Schedule, if I can't get that match it to the SAE spec rather than rely on a civilian do-it-yourself book. What trailer do you have?

[Surveyor]

I try to rely on the military spec laid down in the Servicing/Maintenance Schedule, if I can't get that match it to the SAE spec rather than rely on a civilian do-it-yourself book. What trailer do you have?

 

I have a Penman Trailer and Penman gave me the brake fluid spec, being frugal with money was hoping that the Land Rover had the same spec, at the moment cant lay my hands on an MoD manual to confirm, FOI Request says refer to land Rover

Edited October 12, 2016 by Surveyor
spelling

[DMC 7RU]

Maintenance Instructions for both Penman Trailer and Land Rover TUL/TUM show OX-8 to be used in hydraulic systems

[fv1609]

I use DOT-4 in my Wolf & trailer, what you need to avoid introducing is DOT-5 which is silicone.

[Surveyor]

Maintenance Instructions for both Penman Trailer and Land Rover TUL/TUM show OX-8 to be used in hydraulic systems

 

Many Thanks

[Surveyor]

I use DOT-4 in my Wolf & trailer, what you need to avoid introducing is DOT-5 which is silicone.

 

Clive

many thanks, I see on EBay some one selling a NATO issue brake fluid which seems to comply,

[Sean N]

I always thought OX8 was just standard mineral brake fluid to DOT3, and later DOT4, spec - nothing special. Is there any reason why you can't just buy a bottle of DOT4 off the shelf at the local factors, or am I being naive?

[Richard Farrant]

I always thought OX8 was just standard mineral brake fluid to DOT3, and later DOT4, spec - nothing special. Is there any reason why you can't just buy a bottle of DOT4 off the shelf at the local factors, or am I being naive?

 

In the 1991 issue of Defence Standards, OX-8 was to spec SAE J1703 which is DOT3, but I always use DOT4 which is to SAE J1704

[Surveyor]

I always thought OX8 was just standard mineral brake fluid to DOT3, and later DOT4, spec - nothing special. Is there any reason why you can't just buy a bottle of DOT4 off the shelf at the local factors, or am I being naive?

 

Sean

That's why I posted the question, following research online and the horror stories I thought I would ask the question of those with more experience of working on vehicles than me.

Knowing my luck would buy one off the shelf and find issues once it went in the system and then have to strip out all the brake lines and renew them

[Sean N]

In the 1991 issue of Defence Standards, OX-8 was to spec SAE J1703 which is DOT3, but I always use DOT4 which is to SAE J1704

 

Richard, that makes sense; I don't have a later Def Stan either, but I suppose one might have expected it to be updated to DOT4 as DOT3 is now somewhat obsolete.

 

Sean

That's why I posted the question, following research online and the horror stories I thought I would ask the question of those with more experience of working on vehicles than me.

Knowing my luck would buy one off the shelf and find issues once it went in the system and then have to strip out all the brake lines and renew them

 

My understanding is that DOT3, DOT4 and DOT5.1 are all PEG based fluids and can be mixed safely. DOT3 is somewhat old fashioned and obsolete these days.

 

In recent years synthetic DOT4 and DOT5.1 formulations have appeared, but just as with synthetic motor oils, that doesn't change their compatibility.

 

DOT5 is the silicon brake fluid and can't be mixed with any others. A lot of people moved to it when it came out because it's not hygroscopic, but it turned out it had a lot of other issues and is probably best avoided in standard braking systems. The horror stories you report might be to do with DOT5.

 

I've seen suggestions that DOT4 might not be compatible with seals in certain originally DOT3 systems because of the ester content. Some of the brake fluid and brake system manufacturers recommend sticking to the fluid originally specified for that vehicle in case of compatibility issues, as system components will have been designed to work with the mix of chemicals in use at the time. In general that's a good principle to use; having said that, I've never actually come across any problems despite many years working on vehicles.

 

When I started driving DOT3 was pretty much standard; I was doing a lot of motorsport at the time (getting brake discs glowing orange with use), moved to DOT4 for the higher specified boiling point.

 

I haven't heard any horror stories about DOT4 vs DOT4 synthetic, but then I've never chased them online. I suspect the horror stories might be to do with DOT(x) vs DOT5.

 

I would have thought if Penman specify synthetic DOT4 there's nthing special about it and you could probably get any synthetic DOT4 from the motor factors and it will be fine, but this is only my opinion - the usual disclaimers apply.

 

It's likely the brake system was not made by Penman but by Lockheed, Girling, Lucas, TRW or one of the other brake system makers. If you're still unsure, you could go to them and ask.

[Surveyor]

Sean

I was at Penman today, have to say the aircraft hanger was a great piece of engineering, The charming Jennifer actually made a comment regarding the fluid affecting the seals which was a point made earlier

[Peakrec]

Sean

I was at Penman today, have to say the aircraft hanger was a great piece of engineering, The charming Jennifer actually made a comment regarding the fluid affecting the seals which was a point made earlier

So what problems occur with synthetic dot 5, I was wondering, as a cure to stop cylinders seizing on a ferret ?

[fv1609]

Also bear in mind there is DOT 5.1 that is compatible with DOT 4, but not DOT 5

 

http://www.epicbleedsolutions.com/resources/faq/difference-between-dot4-and-dot51-brake-fluid/

[Richard Farrant]

I was wondering, as a cure to stop cylinders seizing on a ferret ?

Re. Ferret: As there should not be any fluid around the piston, unless the seal is leaking, the liberal use of Red Brake Rubber grease around piston and handbrake piston and in bore, should help. That is what I always do and not had a 'come back' yet.

Edited October 17, 2016 by Richard Farrant

[Surveyor]

So what problems occur with synthetic dot 5, I was wondering, as a cure to stop cylinders seizing on a ferret ?

Jennifer was not specific about fluids but mentioned that there may be an issue with the seals being affected