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TD5 PAS hydraulic fluid - operating temperature


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If you can hold your hand on it, it would be too cold to be efficient. The hotter it gets the more heat energy it can get rid of.

Most of my hydraulic customers start to get twitchy at seventy degrees centigrade. If you are worried, the best way to start is to put a temperature reader on it, so you know your exact hot value. If it is getting to eighty when it is really working hard then it will be pretty thin and maybe time to send some fresh air at the pump?

The old tin can reservoirs were much better at keeping oil cool, but the oil is better at running hot these days.

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The above link may give you an ideal of the viscosity change

Because ATF is used in power steering systems guidance is best sought from the automatic transmission experts which tend to be the Americans. The below link gives some guidance on the effect of oil temps and transmission longevity


These are just some guidance links. Not endorsing them but you get the general idea and you can probably find something more specific or detailed on google with a search. Would not have thought oil temp on power steering in normal driving would be an issue but maybe different if doing a lot of manoeuvring in a trial for example in hot climates like the Mohave maybe??

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Thank you for the data links, robertspark.

I thought the Transmission Temperature vs Miles to Transmission Failure particularly interesting.

Do have a look at my post of earlier today (Not a problem to be resolved, etc. ) to see what was at the root of my earlier question about hydraulic fluid temperature!

Likewise, Team Idris, I was reassured by your 70 deg C figure (above) having measured 65 deg C on my newly overhauled pas system after a good run.

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