Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) brake fluid

just been to the local motorist shop to buy some dot4 brake fluid, but it is all synthetic and you have to really scrutinise the label to discover this.

where is the best place to get mineral dot4? or what make.. it's for a 1985 +8

DB

My understanding is that DOT4 is a synthetic brake fluid and is what will be in your +8

Mineral brake fluid is only used in a small handful of cars.

thanks for the reply tbm, I understand you can't mix mineral(older type brake fluid)with what is now referred as fully synthetic, Opie oils say that all brake fluid is glycol based..

so I am trying to differentiate between the two but it doesn't help. when the brands do not always say fully synthetic on the label.

DB

ps. it is synthetic Silicone brake fluid I am trying to avoid, sorry if I have been misleading ,

DB

Silicone fluid is DOT5 - that does not play nicely with DOT4.

But if it's marked as DOT4, it will work perfectly well with your current DOT4.

DOT 5.1 is the synthetic non anhydrous brake fluid that's compatible with DOT 4 although I would flush to use either one or the other and not mix. DOT 5 should be avoided if brake/clutch components were not designed for it, as is the case with trad Mogs.

Having just bought some yesterday I can add that the current "synthetic" labelling of DOT 4 seems to be a marketing ploy. Its always been a glycol based synthetic and current labelling does not signify a sudden change.

I run DOT 5.1 in Monty, as already covered by RichardV6 if you're stuck you can top up with DOT4 no trouble at all.

DOT 5 on the other hand is silicone fluid and definitely not compatible with 4 & 5.1, I'm just back from the Le Mans Classic and that mistake (by a well meaning mechanic) nealy took the Aston out of the game.



I flushed it through and bled it up on good old DOT 4 and I did get the clutch back, but the slave seals were very swolen and knowing that situation would only get worse I was surprised we we're able to complete the trip. TBH I would'nt have wanted to do another day more because by day six we were getting through a whole resevoir of DOT 4 a day!

Don't mix it folks, as soon as I saw the tell tale 'oil & balsamic viniger' spots in the empty reseviour I knew exactly what had gone on, a classic case of... "A little knowlege is dangerous"

Of course the good old TR3 saved the day, a quick trip to the local mechanic and we were back at the Aston holding a fresh half litre of DOT 4

Sorry to read of the issue and related adjustments to your plans. The brake fluid numbering system seems designed to cause confusion leading to failures and great inconvenience if not worse....My old Mog has run with Automec SBF dot 5 brake fluid in it since circa Y2K, only changed once in that time during a brake overhaul.... Truth be told I have no idea what fluid is in the clutch m.c. though pretty sure Kevin the chap who rebuilt what is now my Mog, would have used the same fluid in both.... The clutch fluid has never been changed, though only covered about 30k miles over the years... Sigh!

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