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Anyone know of a better radiator cap? 88xj


NAXJA Forum User
Huntsville, AL
My "radiator" cap keeps blowin at 215, older style cooling system. I have replaced it with a new one and the same thing. I saw a while back someone found a higher pressure one for a Volvo or something. Can someone provide info please? I know I should convert to newer cooling system but I am running low on cash replacing everything to pass smog. Maybe next year.
Quadratec has the complete bottle and cap for $19.95. If you don't replace both together a new cap probably won't seal to an old bottle.
While a new cap/tank is probably a good idea, a new radiator is probably even better. An old radiator will not cool as well as a new/clean radiator. If it's original, it NEED's a new radiator or you will try everything in the book and still have overheating problems. Then, you will finally give-up, convert to open system (with a NEW radiator) and mistakenly think the old design is/was crap. It isn't, it simply needs a new/clean radiator, tank/cap, fan-clutch and rubber to maintain proper temperature/pressure.
Almost new 3 core rad. fan clutch, new aux. fan , waterpump, everything has pretty much been replaced except the bottle.
jcnoble said:
Almost new 3 core rad. fan clutch, new aux. fan , waterpump, everything has pretty much been replaced except the bottle.

You should've done the bottle/cap at the same time as the radiator. Might have air too? Did you fill the system while level via the upper radiator hose removed from the thermostat housing? I think that's the best way to fill closed systems and prevent trapped air. Otherwise, you might need to burp it by loosening the temp sender on the block. Don't know specifcs though, 'never do it that way.

OMT - did you use teflon thread sealer tape on the e-fan sensor/switch, assuming you kept the closed system? If so, that's a no-no. That stuff seems to interfere with good thermal contact and sometimes prevents the sensor from closing the circuit when it should. No e-fan = get's hot, boils over.

The stock sensor uses only an o-ring and it can be a PITA to seat properly. A little Vaseline or saliva will help installation.

Get a new tank/cap and go from there.
I drilled the thermostat to help it burp. I am using an aftermarket adjustable thermostat for the aux. electric fan. It has a bulb that goes into the upper radiator inlet, works good. I think its a flex-lite thermostat. The only reason I want it to get hotter is to help pass smog, otherwise it never goes above 195, if I have the 195 stat in. Right now I am running a 180 and it takes a while to heat up.
do a search on my user name and you'll find an easy fix that uses a mopar tank with a "real" radiator cap on it.....costs about 3.00 at the U-pull-it....