What would the dates of 99 be for 0331?

 

'00/'01 XJs had the 0331 head. That's why I'm guessing it could be possible for a very late build '99 to have it. Use the search function for 0331 head to find out how to correctly identify.

 

If the production date is from 9/1999 to 12/1999, you most likely have the 0331 head since that's when the 2000's were starting production. I'm not sure how to identify if it's exactly the head though.

 

Im not gonna go back and forth with you about it, but the dealership I worked at and shop I work at now have spent alot of money sending me to school to learn this stuff. And according to the manufacturers, a vehicle that enters closed loop that fast is malfunctioning, and i verified it thru the Chrysler engineers today and again with my Solus today. It took 2 minutes and 31 seconds to enter closed loop with a starting temp of 82 degrees. But hey, maybe they don't know what their talking about either and my Solus is malfunctioning.

To the OP, if you brought it to my shop, I would do exactly what i told you to do. Try it. There was also a post about reverse flow pumps, I forgot about those, would cause it to overheat quickly.

 

Reverse flow pumps? As in water pumps?

When I take the water pump off, can I stick the water hose in there and see how fast the water shoots out of there to see if anything is clogged?

 

Yes reverse flow waterpumps. The impellar is actually reversed. You would still get SOME flow with the coolant riding on the opposite sides of the blades but not enough flow for the coolant to do it's job.

Yes, by all means get water to flush everything out where ever possible. Run it til there's no more coolant and the water comes out clear. Goodluck.

 

I yield, u've got more experience in the area than I do. I'm just going by the fact (and photo) that our XJ, Toyota, Saturn and Ponyota all enter closed loop well before coolant temp is anywhere close to so called normal operating "range".

Engines today warm-up (coolant temp) at about the same rate as they did 40 years ago. However, todays engines run much cleaner/leaner and way sooner because engineers figured out ways to make them run cleaner/leaner without having to wait on coolant temp to rise.

Good call on suggesting 180F t-stat, been running one for 19 mos now, but talk about being critisized. No ill effect here....good heater, good mpg. In January, coolant temp hovers at 180 (scan tool), now (August), will see 210+, stuck in 5:00 traffic, running a/c.

 

Jeep made a mistake by putting numbers on the temp gauge, all it does is breed fear and worry in the average Jeep owner's mind.

 

Interesting read.....heated O2 sensors can reach 500C in as little as 8 seconds......allowing system to enter closed loop fuel control sooner.

http://www.picoauto.com/applications/lambda-sensor.html

 

U callin' us average....WTF? If that was the only mistake Jeep made...............

 

Going to go get a water pump, and gonna tear her down again, im going out for archery deer on Thursday so it wont be finished till about Monday then.

 

Just got that Bosch pump at pep boys, I don't see a r stamped in it anywhere, is that okay??

 

Should have a R on the impeller.

 

There are many reasons for overheating.

Yes, the water pump can be pumping the wrong way. Remember, the 4.0 originally was a 4.2 – with a Vee belt. When they went to a Serpentine belt, the belt turned the pump the opposite way. The impeller was the only thing different. It was reversed so the fluid went the right way. Originally the Serp type pumps were marked with a REV on the front. But through the years since that REV got lost, and rebuilders mixed up the impellers. Most pumps are made in China or Brazil – adding even more confusion. It’s possible to get a Vee type when you need a serp type.

If the wrong pump is used, it will overheat almost immediately! It will overheat the engine, but the radiator will remain cold. Usually within 3-5 minutes.

Always compare the impellers when buying another pump.

If it’s already on the engine, remove the T-stat housing and T-stat. Start engine – coolant should flow out the T-stat well like a firehose.

While the t-stat is out, make sure it has a slot or hole on the flange to let air bleed through. If not, drill an 1/8 inch hole. Put the hole or slot at the TOP when installing.

The belt – serp belts slip – that’s why most use tensioners. If no tensioner, check the tension – where it runs a long ways between pulleys, twist the belt. You should be able to twist it about 90 degrees with effort. If you can twist in more than 90 degrees, it’s too loose. Much less it’s too tight.
Try feeling one with a tensioner to get “a feel.”
A belt that slips will overheat it at higher speeds, especially with the AC on.

Get a laser type infra-red thermometer – Harbor Freight about $30. Handy for lots of things. Measure temps all over the radiator – cold spots indicate plugs in the tubes.

Measure the temps of the heater hoses – in and out – find plugged heater cores.

A stuck T-stat becomes very obvious.

When fully warmed up, rev it and watch the lower hose – if it collapses replace it. That’s the suction side.

Take a perfectly operating system and remove the T-stat – now you have a system that will overheat! The T-stat is a restriction, slowing the coolant down to allow it to transfer it’s heat to the radiator. Without that restriction the coolant goes too fast. Removal will not make it run cooler.

Air is a killer – proper bleeding is critical, especially on the closed Renix system.
Renix - The help you fill it after it’s been open, jack up the rear of the vehicle so the rear of the engine is higher that the rest. Remove the coolant temp sensor at the back of the engine. Fill the system slowly from the overflow bottle – when full, coolant will come out of the temp sensor hole. Let it stand for 5 minutes, try adding more. Replace sensor.

On non closed systems (cap on radiator,) you can remove the front left headbolt to bleed the air out. Use water sealant and torque the bolt properly afterwards.

Be sure the heater controls are set to ON, otherwise air hides there.

Using a lower temp T-stat will not help the engine to run cooler, but it will cause it to run rich, wasting fuel and lowering HP.

A partially restricted exhaust system will also cause overheating – use that infra-red thermometer! Check all along it – where it’s restricted it will be overly hot, then right after that spot it will be much cooler. Constipation!

If a defective head gasket is suspected – check the dipstick for water. Check the oil filler cap – look for brown Mayonnaise looking stuff. Do a pressure test and compression test. Check the exhaust pipe in the rear for coolant!

Check your automatic trans fluid too – a defective cooler can leak. It will turn the ATF milky.

Hope this helps, RRICH

 

Coolant flowing too fast thru the rad is a myth.....t-stat does one thing, control minimum temp....when wide open, the t-stat has virtually no restriction to flow. Many variables effect higher coolat temps....a properly functioning t-stat is not one of them.