View Full Version : 4.0 xj gurus

12-19-2010, 08:08 PM
Got a 88 xj gets hot very easy has a elec fan on it but it's not enough where's the first place to start?

12-19-2010, 08:20 PM
I'm guessing it has the closed system.
Make sure your bottle isn't cracked(need the pressure) and does it just get hot or does water boil back out of the jug

Other than that the regular things, T-stat waterpump( might not be leaking but blades could be corroding away, rad dirty or scaled up inside?

12-19-2010, 08:22 PM
It starts to boil what's the best place to start?

12-19-2010, 08:30 PM
My old jeep with a closed system used to bubble 4L of water out when I turned it off, changed rad and was good after but if your plastic tank has even a small crack it will do that as well

12-19-2010, 08:32 PM
This probly sounds dumb but what is a closed system

12-19-2010, 08:53 PM
If you have a rad cap on your rad it's open,
If you have a stupid plastic jug at top passenger side of engine compartment it is closed.

12-19-2010, 09:01 PM
It has the jug can you swap a open rad in?

12-19-2010, 09:06 PM
Yes you can,

I've only heard of such swap but I would think it's just straight forward, put in open but:dontknow:

12-19-2010, 09:08 PM
The open rad should be the same everything just with the cap no? Does any one got a decent spare rad?

12-19-2010, 09:23 PM
you probly just got an airlock my xj used to do it all the time crack a few of your cooling lines make sure they all have fluid top them up wait for it to overheat again do that once or twice theres a good chance it could help

12-19-2010, 09:29 PM
Does any one got ne spare time to maby come take a look?

12-19-2010, 09:29 PM
Beers included

12-19-2010, 10:22 PM
if your gonna switch to the open system then make sure you get the heater hoses and overflow tank also its an easy swap. takes 20 min . 91 and up xj's have everything you need. if you still need help give me a yell tues i can pop by for a bu and a beer.

12-20-2010, 12:26 AM
I'm gunna track down a rad funds are tight cuz of Christmas

drooling starfish
12-20-2010, 01:04 AM
They don't like low speed crawl'in either. Those things are packed so tight under the hood that there's not alot of air flow so they hold the heat at low speeds. Alot of guys put vents or louvers in the hood and it seems to work great.

12-20-2010, 05:20 AM