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CJwranglerjeeps 03-04-2013 11:24 PM

Coolant Pressure Test ??? Proper radiator cap psi???
Hi there,

1988 Jeep Wrangler YJ re-manufactured 258cu/4.2L, Offenhuaser,Holley 4 barrel- Wrangler tub on a CJ frame, lifted 6"

Water pump gasket was leaking a bit & thermostat gasket. New gaskets, pump installed ...

Now doing the pressure testing again to check my work...

How long should I leave the pressure tester in to test it?

How many pounds should I bring it to?

Should I do test cold or semi hot ?

Should I pressure test it over night, for a 10min, or a few hours?

I've been testing it at 10-12lbs for about 10min, seems to be holding pressure longer then 10min w/ very little drop in pressure. , all seems to be fine, brought it to 15psi, bottom hose leaked a bit.

what is the proper Radiator Cap PSI for a 1988 YJ 4.2L ???
Ive read from 13lbs and or 15/16lbs

Thanks for any help guys, sorry for all the questions....

Cheers AC

jeep63 03-05-2013 05:41 AM

My understanding is 13lbs.

pete1991YJ 03-05-2013 07:10 AM

I've always used 13 or 14 lbs with no probs

CJwranglerjeeps 03-06-2013 07:42 PM

Thanks everyone! Any suggestions for other questions about pressure testing ? Thanks

Que89YJ 03-07-2013 08:55 AM

The pressure test is easy.You pump it up and see if the pressure starts dropping. There is also the running presssure test which is for checking a headgasket leak to the coolant. Sometimes it fails and does not go through the oil jacket just to the coolant. What happens is you will see the pressure on the guage bounce if you run the Jeep while you are checking pressure.

atldude 01-17-2014 02:18 PM

Googled and came upon this old thread so I figure I post up what I found. Possibly covered before but for anyone else who stumbles upon this in the future:-)

From what I read we should be using a 16psi rated cap SAE Range 14-18 psi which is what the FSM ('95) specifies as acceptable pressure range of the YJ cooling system. :cheers2:

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