dogkatcher

90 XJ laredo 4.0 145k, manual trans

so, hopin this cures my backup / overflow / blow out of cooling fluid when hot ..... & weird idle / throttle problems when running cold .. hopin not the head gasket pressurizing it, really dont think thats it since its very infrequent it does that.. I drove 250 miles right before xmas .. Im thinkin the Rad finally clogged up enough & coolant has nowhere to go freely

I already did thermostat .. this overflow occurs very random, sometimes when driving, sometimes after shut off

anyways

got the Redy Rad #432268 since had a coupon .. sticker on new Rad says to goto www.pliii.com .. tried it .. forbidden page came up

what is the sensor on the radiator? viewing posts on here its not the engine temp sensor. guessing the CTS? maybe that colder not circulating fluid is screwin w/ the computer?

and .. the oil & trans cooler ports/parts it came with are not needed.. nor ports look sealed, have a manual trans. are they going to blow out coolant? it came with identical attachments, but they look hollow

kinda scrathing my head at those .. I only got it somewhat ready for the swap tonite, removed the braces for front end & got a good view for 2morrow

AND the sensor mentioned had a crusty gasket between old radiator .. I only backed it out slightly (to see if it would free up easily) & gasket pieces fell out, I tried to tighten it but it had a slight drip when I left

any advice wld be great ... is that sensor really needed? .. seeing it has a quick disconnect .. new Rad has that sensor port plugged, but has an allen key removal it looks like

not sure if I should try to swap the un-needed valve port attachments from old Rad .. or just install the ones they gave me .. are they 1way check-valves?

a quick install wld be nice .. hopin someone can give insight

billfrank85

The "PLIII" website hasn't been online since 2008 or so...here's an archived version, not sure how much functionality you'll actually get out of it though:

http://web.archive.org/web/200808010....com/index.htm

What "sensor" are you talking about? The only connections I remember include the two automatic transmission cooler lines (both have rubber boots on the ends), the drain plug (allen wrench head), and the two radiator hose openings. If you can take a picture, it would help a lot more.

littleredXJ

I gather from your rambling post that you replaced your radiator? The sensor you are referring to is the temp switch for your electric fan. Yes you need it if you want your fan to work. You can leave the trans cooler ports open our capped, doesn't mater nothing will come out. as far a all the problems I think you may have been trying to describe (?) I don't think a simple radiator swap will fix them. Sounds like your pressure bottle is also cracked. Do a search for open coolant system swaps and I think you will find some good info and may save yourself a lot of head ache.

dogkatcher

well .. sorry about the ramble .. just needed some insight .. sick of breaking stuff .. not having all the parts needed .. and job done right 1st time

so, yea littleredxj said thats the Cooling Temp Sensor .. and the extra RAD ports will not do anything if left open .. so true .. thanks man !!

got new Rad installed today .. took my time & it paid off

The issue was coolant blowing out of the bottle randomly & engine got a bit too hot twice. Thermostat job 2 weeks ago didnt help

I was thinkin the coolant was limited to flowing only thru the engine & to bottle.. seemed to be the case .. radiator gets warm, old one did not

thanks for your help!

Does that Coolant Sensor also contribute to computers idle - fuel mixture??

or just E-fan ?

since old radiator never got hot, CTS was always reading wrong .. was running rough sometimes, she drove like a champ after install 2day .. hopin that cured the weird idle / accel.

littleredXJ

So hopefully your problem is fixed but here is a little more info fyi: your jeep (90 and older) has a closed cooling system. This means that you have no radiator cap and your entire system is under pressure, including the plastic over flow bottle. So if you are leaking coolant from the plastic reservoir then it is cracked (very bad) or your engine is seriously over heating. The plastic reservoir is a common failure point on the closed cooling system. The sensor on the radiator is only for the electric fan, more of a temperature switch not a sensor. The sensor that your computer uses is on the driver side of the engine block and the sensor for your gauge is on the rear corner of the cylinder head (yes you have 3 temperature sensors). As I mentioned in my last post, you should look into converting your cooling system to the later style open system (radiator cap and none pressurized reservoir) but at the very least make sure your reservoir is not leaking because it is an important part of your cooling system.