After trying multiple times trying to have my turbo brass radiator repaired I finally switched to the thinner Nissans I found at a PYP yard. It worked fine cooling the engine but the sudden increase in hot air when the fan clutch engaged caused the clutch cylinder seals to start leaking and loose pressure. It would come back after things cooled off. The master brake cylinder eventually failed also which was the final straw in me donating the car. Any one else have any problems after starting to use the Nissans?

The aluminum-plastic radiators actually work much better to transfer heat away from the coolant than the brass-copper radiators. I could try to explain how, but it's not easy for me to do. Mostly there are more connections and heat is more evenly/quickly spread around the radiator.

Anyway, the fan is always engaged on these - there's a viscous clutch which will disingage partly when it's cold and engage fully when it's warm. The logic is that a hot fan clutch means a hot engine and a cold one means a cold engine.

If the viscous clutch was leaking, I would think that the fan clutch was not working right - probably not engaging enough when it needed to be. The force of the fan blowing will actually blow hot air OUT of the engine bay. A buildup of heat in anything, like the clutch cylinder, is more likely to be because of a bad/slipping/too-slow-to-engage viscous clutch.

I've never seen a fan clutch fail to where it was spinning too much, only to seize up and be 100% engaged all the time.

How did you know it was a heat issue with the hydraulic clutch?

Happy Bricking

In stop and go traffic it would show up every time like clockwork a short time after the fan clutch engaged. I even tried wrapping the clutch master cylinder in pipe insulation but it did not help one bit. I've been driving stick cars for over fourty years and have replaced my share of clutches, slave and master cylinders. Never had one do this before. It must be heat related though because as soon as the engine cooled down the clutch came back as good as new.

I'm not clear on what's described. The fan clutch engages, so fan is moving? or not moving?

How can there be a rush of hot air??

When the fan clutch engages there is a definite VERY noticable VERY increased sound of rushing air in the engine compartment. After that starts I can almost count the exact number of stop and go clutch uses before I start to loose pressure. I'm only assuming that there is an marked increase in engine compartment air temperature when this happens. There is absolutely NO CHANGE in the engine temp gauge.

Still scratching my head. I can't see how it's related to radiator.

Is the fan installed direction correct?

"start to loose pressure" ?? Coolant is leaking out?

Don't have the car anymore so can't check the fan. The way it comes off with the four bolts means it only goes back one way. I don't think it was reversed but....? I was all ready to replace the flex clutch hydraulic line when I gave up on the car. Had it almost 15 years. No slave cylinder leaking either. Very odd problem.

"I was all ready to replace the flex clutch hydraulic line when I gave up on the car."

Well there's your problem...you had a hydraulic line running to a sealed unit. The fan clutch (I have to assume that is what you are talking about here) is fully self contained and actuated by heat. Was it installed the same time the muffler bearings were changed?

There is no way that a properly function cooling system, including the fan and fan clutch, could cause health master cylinder seals to fail. Even on an old oil-cooled turbo Volvo 240 which could blister the paint without the hood blanket.

Sorry for confusing you. I'm talking about TWO different things here. The fan viscous clutch actuated by heat and the transmission clutch actuated by the hydraulic master cylinder. The Volvo hydraulic clutch system has a section of flexible line going to the slave cylinder. The muffler bearings have absolutely nothing to do with either system.

ahh.... of course, MUFFLER BEARINGS ! ;-) I'm glad someone here still has their bearings...

You kidding...I removed mine immediately and got 20 more torques as a result!

The plastic-aluminum radiators are stock in the car so your problems with seals were elsewhere.
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See the 700/900 "FAQ" at the menu bar top screen left side.

The older late 80's turbos come with a much thicker brass radiator as stock.