Operating Temp Help

Ok so I have a 2000 XJ 4.0L 110k miles hood louvers, and its approx 30 degrees ambient temp outside, (this may come into play). My old water pump was leaking from the weep hole.

I replaced the water pump and stock thermostat with 180 degree thermostat because this past summer I had issues with the jeep running around 220 degrees when wheeling. After replacing the water pump and t-stat I realized the Jeep failed to heat up to operating temp, hovering at only the second "tick" on the temp gauge and I had no heat in the cabin. As the upper rad hose was hot and firm I opened the rad cap while the jeep was running, coolant and air spewed out, although the coolant was cool to the touch.

After this the jeep began to warm up to operating temp, about 180* indicated on the temp gauge. I figure i must have burped out a large air bubble. However i can now remove the rad cap while at operating temp without any pressure or coolant coming out. The coolant is at the top of the radiator with the engine running/warm or cold/off. the overflow tank also always reads full.

Why do I have no cooling system pressurization? Is it possible with 180* t-stat and louvers in the hood my cooling system does not reach "boiling" when the ambient air temp is 30*? Any help is greatly appreciated, thanks guys.

You may have damaged the pressure cap or reinstalled it wrong. I usually have to replace them every 2nd coolant change.

13lb relief cap from NAPA like this

You may have damaged the pressure cap or reinstalled it wrong.

13lb relief cap from NAPA like this

:doh:

First, your thermostat has nothing to do with your cooling system's ability to transfer heat. Install a stock temperature thermostat so the ECU and engine oil can do the jobs they are designed to do.

Second, are you losing any coolant?

poppyseed said:

I replaced stock thermostat with 180 degree thermostat because this past summer I had issues with the jeep running around 220 degrees when wheeling.

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I thought I raised you better than that-- put the 195* in and let it run at 220* like it's supposed to:dunce:

I'd be looking for places the cooling system can bleed pressure easily-- the cap would be my first check and the 0331 cylinder head deserves a check too (along with any hoses you've touched)

Shorty said:

I thought I raised you better than that-- put the 195* in and let it run at 220* like it's supposed to:dunce:

I'd be looking for places the cooling system can bleed pressure easily-- the cap would be my first check and the 0331 cylinder head deserves a check too (along with any hoses you've touched)

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Lol and I always believed it and still do. I too am apprehensive it will make any difference in the summer, however its undeniable my temp gauge is reading 30* cooler now than it did last winter.

I did check all my hoses, replaced the cap and checked for chrysler made chocolate milk. Everything checks out. I have a feeling with the tstat opening at 180 the coolant never gets a chance to get hot enough to expand enough to pressurize the system.

And it did pressurize when it definitely had air in the system so I'm at a loss :/

ehall is trying to tell you that your cap may not hold pressure, hence no pressure. Replace it and see if it helps.

Don't ask for help and then ignore the help.

do you still have good heat? May still have air in the heater core.

Buy a new genuine Jeep 16 lbs radiator cap, and a genuine Jeep 195* thermostat. I would guess that the 185* thermostat is defective.

You should NEVER remove the radiator cap when the engine is hot, but if you were to do so, boiling coolant should spew everywhere.

My 2000 runs at 195* when it is 20 below zero, and it has hood louvers.

RedHeep said:

ehall is trying to tell you that your cap may not hold pressure, hence no pressure. Replace it and see if it helps.

Don't ask for help and then ignore the help.

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I did already replace the cap as mentioned. Dont offer help and not read.

Shorty said:

do you still have good heat? May still have air in the heater core.

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yes I do have heat after the initial "burping" of the cap

Tim_MN said:

Buy a new genuine Jeep 16 lbs radiator cap, and a 195* thermostat. I would guess that the 185* thermostat is defective.

You should NEVER remove the radiator cap when the engine is hot, but if you were to do so, boiling coolant should spew everywhere.

My 2000 runs at 195* when it is 20 below zero, and it has hood louvers.

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I could tell it wasnt hot as the cap was cold to the touch. I used a rag and opened it slowly.

The correct cap for your 2000 is a vented cap. It won't build pressure in the system like a non-vented cap. It takes a while and a large pressure change for it to hold.

See here: http://www.naxja.org/forum/showthread.php?t=1109836

What you are having happen might be normal operation for that cap.

I think I'd still go back to the original temp thermostat and recheck for leaks.

Is there any chance that the filler neck on the radiator has any damage preventing a good seal from the new cap?

It wouldn't hurt to have the cap pressure tested or replaced again on the off chance it was damaged/defective from the start.

Talyn said:

The correct cap for your 2000 is a vented cap. It won't build pressure in the system like a non-vented cap. It takes a while and a large pressure change for it to hold.

See here: http://www.naxja.org/forum/showthread.php?t=1109836

What you are having happen might be normal operation for that cap.

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very interesting, indeed-- everything might be working correctly.
Thanx Talyn, for that bit of new info to log away somewhere I'll never be able to find when I need it!:wow:

Im convinced I must still have a small amount of air in the system cushioning the expansion of the coolant if you will. I most likely will go back to the stock temp thermostat as I dont see how it would make a difference in the summer either. I think I'm seeing lower temps right now just due to the cold air keeping the system at/near the thermostats opening position.

Talyn said:

The correct cap for your 2000 is a vented cap. It won't build pressure in the system like a non-vented cap. It takes a while and a large pressure change for it to hold.

See here: http://www.naxja.org/forum/showthread.php?t=1109836

What you are having happen might be normal operation for that cap.

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Awesome link. Thank you. I bet this is exactly what is happening. My cap is from oreilly auto and it was some generic white box store brand but I imagine its the same design. Ill check later today

NAPA sells 4 caps total, 2 at 13 lb, and 2 at 16. The ones without the lever say NON-VENTED and will not work. The ones with the lever work properly. I haven't tested any of the caps from the other chains. With the right cap, air will be expelled and coolant drawn in, as needed.

If you think you have a leak rent a cooling system test kit and check for leaks. Check all the hose clamps as well.

ehall said:

NAPA sells 4 caps total, 2 at 13 lb, and 2 at 16. The ones without the lever say NON-VENTED and will not work.

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Part number BK 7031699 is a vented cap w/o the lever. Spec'd for a 2000 XJ 4.0l when looked up on their website. http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Radiator-Cap/_/R-BK_7031699_0441417872 The lever is not the part that is doing the venting in this manner.

My post referred to what came back for my 1991

I know the lever doesnt do the work.

last night i drove around and the temp gauge never got above the second tick mark and no heat coming out of the vents. Put a 195 thermostat back in today. Waiting on the rtv to cure and we will find out. If that and bleeding the air again fixes my issues