Rob Cleminson

Hi, I'm looking for some pointers to diagnose a 1996 4.0 running hot. Here is what has happened and what I've done to get to this place..

• engine badly overheated - HG and head cracked(0630)
• replaced head with a refurb 0630 head from a '98
• new head didnt have temp sender port at back so I added a brass T-piece in the top hose nr the thermostat housing with a new sender - pic attached
• installed a new T-stat(195*)
• installed a new rad cap
• flushed cooling system with cleaner
• radiator overflow hose was completely blocked with rusty muck so i cleaned that along with expansion tank
• both clutch fan and electric fan work
• clutch fan appears good as when manually spun it only turns a little

Symptoms

• engine gets up to operating temp(210) quite quickly and continues to 225-230 and stays there
• I can get temp down to 215 if I turn heater on either using hot AC or cold AC
• doesnt matter if its idling or driving at 30-50, the temp still seems to run hot

• I did notice a small amount of coolant on the floor after it ran hot but have yet to find the source but am guessing waterpump

the previous own did say he had replaced the waterpump twice in the 15 years he owned it. Would you suggest this is a good item to replace given my symptoms as I cannot think of anything else except the radiator which seemed to flow easily when I passed fresh water through it.


Any pointers/advice welcome


thanks

Hommersimpson

sounds like radiator plugged

Rob Cleminson

i was going to ask about the rad as it takes for ever dribbling water in to fill it up, is that normal?
when it gets to temperature i can squeeze the upper rad hose and with the rad cap off get a lot of fluid movement

drewactual

if there was enough crap to clog your overflow/degas lines, how much of the same do you reckon have stationed themselves in those fine passages in the radiator?

you can clean it... true... you can take it to a specialty shop, and they can REALLY clean it... but... pssst- amazon has an all aluminum 3 row for less than a benji and a half... the only negative? the 12# cap is crap.... get a new 16# and pay close attention to how it seals. (make sure it seats right).

also, and just because i'm on the topic- get one for a manual trans and put a plate style 20k BTU oil cooler behind the radiator instead of using the rad core for trans cooling... just a thing i do that would take to long to explain, but which makes considerable sense unless you live in the great white north and experience negative temperatures- and even then, do the same but install a thermostatic by-pass valve.

BlueRidgeMark

I'm not sure you are going to get a valid reading from that location. It may be accurate for that location, but may not equate to the standard location. Have you checked it with an IR thermometer?

Other than that, see my sig, #4.

mikesignal

^^ yep-check with IR thermometer or scanner. My sending unit was toast and the gauge was not reading right--even from the correct location

Rob Cleminson

225-230 is idling or driving in cool weather and i can drop that by blasting the heater

Rob Cleminson

i just ordered some Amway SA8 detergent as i think a thorough clean is the best starting point before i buy a new rad as i dont want to clog up a new rad

thanks for the advice guys

Rob Cleminson

So today I drained, flushed everything multiple times and installed a new Stant thermostat. I get the same idle and running temps.
I bought a ir thermometer and at operating temp the thermo housing reads 205-210, the back of head where thermo sender used to go reads 225 and the driver side front engine core plug reads about 230. My dash gauge reads 225 unless u blast the heat when it drops to 215 and this is the same driving.

Do these temps seem normal?

I noticed when idling if I leave the rad cap off the coolant never seems to get hot, only when I reseal and switch engine off does the level spill over.

Should I still change rad?

Hommersimpson

one of two things.. blown head gasket... or radiator.. if you are 100% sure you have not popped the gasket or cracked the head.. then put a radiator in it..they are not that much.. and if you plan on keeping jeep.. then that is one less issue you know is ok.. when i put used motor in 70k miles ago.. that had 145k or so.. i put new pump stat and rad in.. it runs 195 in florida heat..

Hommersimpson

Want to know how to back flush the Radiator ?

Rob Cleminson

I have a new head and gasket so don't expect those to have gone again. I ran hose through top of rad until clear water came out, I spent sometime running through the two heater hoses until clean and then through the water pump tube.
Am I missing something to properly flush the rad?
Having asked this I'm going to buy a new rad anyway to be sure

Hommersimpson

When you get old one out.. pop the tank off on the side the upper hose goes to..
Now.. on back flushing.. if you take both hoses off at engine .. point the upper one down towards the ground.. take a rag.. and garden hose with a good flowing nozzle and put in lower hose.. turn on full blast.. when water comes out other hose let off nozzle.. then squeeze real quick and let off then on again.. if you have compressed air.. then use that instead.. look at what comes out.. bunch of trash ? or nothing? if trash then its pluged if nothing but clear water comes out then its either 100% plugged or clean.. lol

p/s: if you blow radiator apart.. then it was plugged..

Rob Cleminson

Can I ask, with the engine at normal temp should I be able to squeeze the upper rad hose albeit quickly as it's hot? Or should it be tight with water flow?

mikesignal

I would be curious to know what it is reading on a scanner. You can get an app for android devices or apple devices, then connect with this, or something similar. Although I have read that 1996 XJ's can be tough to interface with OBD2 connectors.
https://www.amazon.com/Bluetooth-Dia.../dp/B0051CAE1C

..or bring it to an auto parts store they will scan it for free, and they should be able to tell you what temp it is,