So I am still getting a bit of coolant loss. Head has been checked - its not cracked. As the overflow bottle is plastic and the cap the same, surely this can't be considered a closed system - any hot liquid is going to evaporate a little bit - ESP the water portion of the coolant mix? If its not the head, any other ideas/thoughts?

 

1. How did you check the head? The devil is in the details here.

2. Older OEM style radiators have a bad habit of cracking at the plastic seams which can lead to a small loss of coolant. Happened to my 99. Couldn't detect it until the leak got a bit larger.

3. You either have a leak OR you are burning coolant. And if you're burning coolant, it is likely to be your cylinder head.

 

LOL there's a sig in that line djb.

 

Thanks tj. The head was checked at a dealership, after earlier posts on the subject I asked them to check it out. Not sure how they did it to be honest but they said it was fine. No reason not to trust them. Radiator may be the problem, I was going to replace it soon anyhow. The amount of coolant going is about 2 inches every 3 or so weeks. There is no oil in radiator, check under the cap often and temp gauge always reads a steady 210 an recently got new thermostat and oil sending unit. Never over heats and everything else running really well. When's the best time to check coolant levels btw? Manual says when engine hot. Do you agree?

 

Yes, check it with a hot engine. Need to be consistent about checking it either hot or cold as it will vary more than a few inches in the coolant reservoir.

Hope the dealer either magnafluxed or pressure tested the head because it needs specialized testing to be sure there are no cracks. You may want to specifically ask them how it was done.

 

i'll ask them and see what they say. Any other thoughts on what may casue a loss if it's not the head?

 

2 inches of coolant use in 3 weeks is not a tremendous amount.

I'd be darn sure that your radiator isn't leaking.

My original radiator in my 99 was leaking approximately that amount when one of the plastic seams of the radiator was cracked. It was very difficult to find that leak until it got worse. And then it got worse FAST. That is the danger here if it is a radiator leak.

My advice is if you need a radiator, replace it NOW. And if the water pump is OEM, you should install a new one of those too while you're into the mess.....You need to do everything you can to keep the cooling system up-to-snuff on any vehicle, but on the 00-01 it is especially important as an overheat virtually GUARANTEES you a a cracked head.

A new radiator and radiator cap, a new water pump and a new Jeep 195 degree thermostat, and don't forget to check hoses. All money well spent.

Good luck!

 

thanks tj. i already done the thermostat, will get on the rad and water pump. like i said was going to do it anyways, but will now do it sooner rather than later. thanks again, awesome advice as always!

 

Just a heads up. I think I read when you last topped it off, you did so when the engine was hot? If so, then when the engine cooled off, then the level inside coolant overflow would naturally drop. I always wait until the engine has sat before I add coolant simply because it will look like you lost some when the engine cools down. The reason the level went up one of the times you checked is because as the engine gets to OT, some coolant is pushed out through pressure (the rad cap) to the overflow. When the engine cools off, the coolant is drawn back in.

I'd say start with a clean slate now and fill the full line WITH THE ENGINE COLD. Monitor it from there. If you're still losing, something is leaking. I'd highly doubt it's the cylinder head. Even the 0331 head only seems to crack when it overheats. No milk in the oil right?

Another place I've found that the 4.0 likes to leak just a little bit of coolant is the t-stat housing. I had coolant loss once, and took forever to find out the gasket had simply worn out.

 

My radiator had a slight seeping next to the drain petcock
where the plastic tank joins the core on the passenger side. Didn't realize it until I pulled the grill. Coolant loss was very minimal, got lucky and found
it early. New radiator at Autozone today $109.

 

I actually topped up when cold, so going off that level. No milk in the oil far as I can see. I did see another linked thread on another site about cracked head issue and a link to a company that runs tests on your oil to see if there is coolant in there - seems a pretty foolproof method of checking - so going to do this as well as the new radiator etc. thanks for the advice

 

If anyone interested, this is a pretty extensive thread/survey on cracked heads:

http://www.jeepsunlimited.com/forums...d.php?t=391831