Hi everyone
I had a bad leak at a union (feed side). So I replaced the seals but it still leaks.
Am I fitting the seals incorrectly? How should it be done?
Any advice appreciated.

No parts of the old rubber sleeve joints left behind? It should be put over the tubes and when you screw the flange te rubber is pushed wide and closes the gap. New rubbersleeves should be soft and flexible.

Thanks AZL
I did look for bits of old seal. I think the pipe under the union has corroded and cracked and is opening up under pressure.
I've bodged it for the moment with a good leg from annother damaged cooler to test my theory and have connected up with rubber pipe (300 psi) and 5 clips ( flat ones not jubilee). Not leaking at the moment.

I think that joint may fail.
Try these
http://www.ebay.co.uk/itm/Pack-of-2-x-1 ... Sw5ZBWNo2z

the aluminium tubes get very brittle when old. And can crack very easy than.

Thanks guys
SP. Would you consider the compression fitting as a permanent fix?

I would use them, but examine the pipe for fatigue as AZL57 pointed out.

Cheers Pete

You might be checking for some considerable time, as I've had a car running using a compression fitting repair on one of the oil cooler legs for over 20 years.

Anyhow, why should fatigue be a problem?
The tubes are only required to resist an internal pressure that's low relative to their bursting stress; it's crevice corrosion at the capillary joint between the steel bush nut and the alloy tube which is the main problem.

Wrapping the tube with PTFE tape when installing an oil cooler helps to minimise that weakness...

p.s. @Roger,
did you check the 'leaky' pipe to see if its diameter had been reduced at the point where the rubber seal sits?
Over-tightening the bush nut can compress the tube, after which the joint will leak.

Thanks Guys

Ken
I had thought it may be corrosion at the union end, but rather now suspect it to be 'user error' in that I may have over tightened it whilst trying to cure the leak. It was ok for about a week before it leaked again.
I'll fit the compression fitting, then see about getting it cleaned up.

Cheers