NathanJay

Maybe there's something going on with the water pump?? If it's not circulating coolant properly and it's sitting stagnant it could cause it to boil. If the thermostat is working properly it would still allow some flow in to the head when it opens (you said you could feel the flow when it opens), but if that's as far as it can go without the pump circulating it might be overflowing into the catch container as it heats up more.

Pelican

What temps are showing as you go through the warm-up and overflow cycles?

slownis

I will get back to you on that. I've switched gears for a bit and have been looking at the broken A/C. I've removed the a/c condenser, which is clogged. I can't blow through it. A new condenser and accumulator are on order. I'm planning to flush the remaining components (including the line with the orifice tube), install everything when it comes in, vacuum it down, then charge it back up.

Can I replace the head gasket - if it comes down to it - without having to evacuate the A/C lines again?

There are some rust colored flakes every time I take off the radiator cap. So my plan while the condenser is out is to flush the radiator while out of the car, and back flush the rest of the cooling system. Then I'll put everything back without the a/c condenser and test it out, making sure I have the proper coolant mixture, and making sure its well burped. I'll make note of the temps of when it starts to boil over and when the efan comes on.

Firestorm500

It never ceases to amaze me when we see boiling coolant/overheating engines on these forums, the poster starts chasing A/C problems or burned out light bulbs, or some minor thing like that.

Especially on a recent acquisition.

The elephant in the room is the probable busted head or blown head gasket.

slownis

Ugh, time to rant.

It never ceases to amaze me when a board veteran starts talking about a newcomer in a derogatory manner and in 3rd person . Great way to make a person feel welcome, that.

I'm sorry, but I live in Texas, and in Texas A/C is mandatory. I verified the A/C was bad with a good set of guages. I can post a video of the observed symptoms if you like, but I don't need help with that. I've worked on A/C countless times. Just because I'm new to this forum, doesn't mean I'm fresh meat. I'd wager I know more about A/C work than alot of people who have posted in this thread. How many people have rebuilt engines with nothing but hand tools and then drive the same car another 60k miles before selling it for double book value? How many people have changed the headgasket on multiple vehicles more than a time or two? In fact, if you google "slownis", likely on the first page you will see a thread in another forum where I replaced the headgasket on a vehicle that was also not exhibiting clear signs of head gasket failure. I did replace the headgasket that time, and have had people PM me for help several times since who have had the same issues. My point is, I have plenty to offer this board in the way of advice and experience. Don't go talking above people you know nothing about.

So lets talk about the "Elephant in the Room" that I've done 3 diagnostic tests, all of which were inconclusive, that I asked a question about in my very last post. The reason I don't dive into ripping the head apart is because the only evidence I've got for a blown HG or cracked head is that my coolant boils over at low temps. The other reason is that to do a head gasket right, it costs money, and I don't like to throw away dollars.

Firestorm, you have said "Head Gasket" twice in this thread without giving any reasoning to back it up. That's worthless to me. Over the years I've learned to ignore people who do that, because over half the time they are wrong. What makes you think "Head Gasket"? Give me something I can work with here before you go making derogatory comments.

Jharris09

If the water pump is the original pump that came with the Jeep, it is probably bad. If it were my Jeep I would do as you mentioned, drain all coolant, use the hose and wash everything (heater core, head/block, etc.) out and replace the water pump. The metal fins are probably gone by now. It is a cheap and easy repair. I have had 2 Jeeps and both needed new water pumps and both overheated. If this has already been changed, then I would still do the complete flush. It looks like your system is overfilled with coolant.

CCKen

slownis,

How old are the radiator hoses? Specifically the lower hose.

Take a look at them (lower) and see what it looks like.

If it is the original hose(s) there may be a spring in the lower hose. If the lower hose is a POS aftermarket hose it won't have a spring inside of it, but that's okay with Gates hoses, and a few others. Without a spring, and suffering with age, the lower hose inside liner may be seperating (disbonding) from the hose body, and under high coolant flow the inner liner may be collapsing and resticting flow.

High School: Increase velocity-decrease pressure.

I ran accross this on a C-46 airplane, only it was an oil inlet line to the oil pump. As I increase the engine RPM, the oil pressure would drop, decrease RPM, the oil pressure would increase. Remove said hose and looked inside - yep, I could see that the inner liner was busted loose.

Thinking outloud as usual....

slownis

Thanks CC Ken,

I did see the spring in the lower hose when I had the radiator out yesterday. It doesn't collapse.

New details:

I can feel the upper rad hose get hot - too hot to touch even - when the guage reads around 195 - 200. The thermostat is working perfectly.

The electric fan kicks on around 215 or so and stays on.

The heater hoses do not get hot.

I can leave my hand on both heater hoses all day and they stay the same temperature - not hot. By contrast if I try and touch the upper radiator hose, I can't leave my hand on it at all or I would get a nice burn.

I attempted to bypass the heater core by bending the heater inlet hose around and connecting it to where the heater core outlet hose hooks up to the metal pipe coming from the water pump. This is after I blew a bunch of brownish/reddish gunk out of the heater core with a garden hose. I think water has been sitting stagnant in the heater core for some time, rusting it up.

Even with the heater core bypassed, the hose does not get hot.

NathanJay I think you are on to something, because that tells me something is probably wrong down in the water pump. Maybe someone got a little two liberal with the RTV, blocking off the heater core passage. I'll get the water pump off later and investigate.

NathanJay

I had a similar brown sludge spitting out of my heater core when I flushed it a couple months back. My heat did not work at ALL, and after removing the blockage/rust out of the core it's like a sauna inside when I turn the heat on. Any way...

It could be a combo of the 2, core and pump. If the core was clogged maybe it had an adverse effect on the pump which could have caused/helped it to fail. That and a couple globs of RTV (like you said) and well, you've got issues.

I hope this is the last place you have to look for a fix. Let us know what happens.

Firestorm500

Ok, slownis, it's your money and your Jeep. You can spend your money however you want. I firmly believe in that.

But you came here for advice. It may not be delivered to you in a manner that you like. Someone may tell you something that you don't want to hear. That might go against what you hope to be true. But that's a risk you take when posting here or anywhere else for that matter.

You don't know me. You probably haven't researched my past posts on here. That's OK, I don't expect you to. But whether some one has one post or 10,000, I treat everyone the same. Sorry if you don't like that.

Now back to business. This is a quote directly from you: "I'm leaning towards head gasket though". I hope it is as simple as a water pump. But if it's not...well.

Now here's something you might want to research. I read somewhere that some 1999 4.0s have the infamous and dreaded 0331 head on them. Those heads have a known casting flaw around the #3 cylinder area that is prone and even likely to crack, especially after an overheating episode. But some can and do crack under normal use. These heads were definitely used in 2000-01, and you will see numerous posts on here from owners of those.

1. We can tell the previous owner knew about the overheating problem. They replaced the radiator hoping to fix that. But it didn't.

2. The heater core is clogged. You system doesn't have a heater control valve. The blending is handled by the blend doors in the box under the dash. The best way to clog a heater core like yours is to introduce block seal or stop leak stuff into the system. So they are trying to do...what? Seal a head gasket, cracked block or head.

3. I live in Arkansas, so you can't tell me a whole lot about the need for air conditioning. We can get every bit as hot as Texas, AND we have more humidity than most anywhere in Texas. I understand that it is fun for you to work on A/C, and that you apparently gotten tired of trying to find out why your Jeep is overheating. But why would you want to spend time and money on something like that right now? You've got a Jeep that can't be driven very far on a test drive even. Not even long enough for your A/C to cool down the cabin. And that working A/C is going to throw even more heat at your cooling system. It can't even handle what its got right now.

My earlier post that upset you wasn't directed solely at you. You don't have the experience on this forum that I have. There are people on here that have vastly more experience and knowledge than I have. But we really do see people chasing relatively minor side problems when they really should be addressing the primary problem.

I myself have done that. I'm trying to give you the benefit of my experiences so that you, and others who might read this, can save time and money by avoiding playing with the side problems until the main problem is fixed.

Or you decide not to spend any more money on a problem vehicle, and get rid of it.

I wish I would have had a Forum like this when I was coming up. It would have saved me a lot of time and money.

CCKen

Water pump - maybe. We'll see...but...

I think you have some serious blockage in your head. The top hose (outlet from the head to the heater core) is free flow. Maximum flush is in order says I.

Firestorm500

Quote: "I think you have some serious blockage in your head."

Well, I do get some serious sinus headaches fairly often.

I wonder if a big chunk of block sealer around a crack in the head would cause this?

slownis

Were finally getting somewhere. I'm not sure how the coolant circulated at all:



I have the same problem this guy had, except he never mentions water boiling out in his TJ. Well hopefully this fixes it, if not we'll see.

Rockfrog

Impeller vanes? We don't need no stinking Impeller vanes!

Wow! Coolant does expand as it heats up, and the system is designed to hold 16psi and then burp the rest to the recovery tank. As it cools it pulls that back.
Definitely the source of overheating there.

CCKen

Looks like a Chinese throwing star. LOL