OK, so this post is two issues that are annoying me. The vehicle in question is a 1997 XJ running a 4.0. Bubba got into it and I'm undoing the damage.

I just completed a head gasket job. Obviously I replaced all the seals above that, head gasket, valve cover, manifold etc. While I was at it I cleaned the heck out of the head and the manifolds.

So, she started up pretty well after being put back together with the expected rough idle when she first restarted. That particular problem has not gone away. She starts like a champ but idles roughly for the first minute or so. I didn't replace the injectors on this girl yet, just the injector O-rings. Honestly, the fuel rail looks a bit beat and I'll probably replace the rail and injectors here once I get everything else ironed out but is there anything else I should look for in terms of dealing with that rough idle given that she didn't have this problem before? This problem lasts a minute to 90 seconds at ~500rpm before she jumps to about 1K and then settles back down to a bit less than 1K and runs nice and smooth after that.

The second issue is a bit more pressing IMHO. When I tore the engine down the first thing I did was attempt to cycle water through the coolant system. This, predictably blew out a lot of crap. Cool. Broke her down, cleaned everything including the thermostat and housing etc. Replaced those seals too because Bubba thought that just smearing RTV on there like a child's fingerpainting was a good "solution" to a $5 problem. *facepalm*

After I got done and put her back together, when I went to refill the coolant I again flushed with hose water and got out a ton more crap because I'd hit the parts of the water jacket in the block, the parts I could access, with a nylon brush. Ran water til it went nice and clear and then for another few minutes. Even cycled the engine to get some force going in there. Once that was done I reconnected the hoses and started refilling her. But when it came time to run her and get fluid into the heater core I noticed something odd. First, she was very slow to take coolant into the heater core. Then she'd blow a ton of fresh antifreeze/water all over the place around 160F and then, if you let her, suck down twice as much. This occurred twice but as near as I can figure there are about 3 gallons of 50/50 in there. At that point the heater started blowing nice and hot. Nice.

Then I discovered that the coolant overflow bottle was full of... mud? Rusty colored mud like the stuff that I flushed out of the system and A LOT of it. Like... 2.5" deep. It also contained chunks of black... stuff that were hard. The smell was... ugh.

So, I cleaned that out really well by taking the bottle off and running water through it until it went clear. OK, cool. Refill to the Fill line so that if the system isn't full I can let it heat/cool and suck in some more coolant.

Finally today I'm getting rid of the serpentine belt squeal (success!) and right after I get done with that I notice that the radiator cap is leaking at around 160F, the same temperature where she's spit out a bunch of coolant and then sucked in more before. Air bell?

No other leaks, just the cap. No biggie to replace it but now I'm starting to wonder about that overflow hose being jammed up with something because, honestly, those black chunks seemed like they were a bit large to get into the bottle. This makes me a bit nervous. I'll hit the store this afternoon for a new cap but I wanted to put this out here for some of you guys with more experience. Is there anything else I should really look at here so that I'm not spending half the day going back and forth to a parts store?

Other than this issue and the rough idle on startup she seems to run like a champ. Much better than before (shocker, right?). But.... coolant problems could kill the engine I've put this time into so... ideas?

Thanks guys!

 

Failed radiator cap not holding would be the first guess. Possible the previous owned mixed old-school green with new school orange? That can react and turn into brown goo.

 

This was indeed one of the problems. Replacing pressurized the system and caused hot coolant to flow into the overflow bottle and... turn black before being sucked back into the system as it cooled.

Goody gumdrops, another flush.

 

Its because you call it a she, way too much 🤣

But ok, on to the issue;
You cleaned the block as you said and cap def leaking.

Other parts that can release crud: radiator, heatercore (although quite small) deteriorated hoses, just to name a few.

Whats the condition of those radiator and hoses?
How do you refill?

 

All vehicles are feminine. To refer to them otherwise is disrespectful and therefore bad luck. (I spent too much time around boats and ships.)

The radiator definitely has some brown in it as a fairly thin coating. Hoses are similar but less so. The only one I don't know much about is that radiator -> bottle overflow. I just forgot about it until yesterday. Other than that the hoses are... 8-9/10. They could be replaced but I wouldn't say it's critical. The rubber is nice a supple with good flex.

If I were asked were most of this is coming from it's coming from the water jacket on the block, because that's the area that I could clean the least other than blowing water through it.

Refill process was as follows:

I disconnected the lower radiator hose and ran water through from the cap until it went clear. Switched to hot water (I have a hot outdoor tap) and repeated the process then back to cold to cool it.

I then repeated this process on the heater core and on the thermostat housing with the lower block hose disconnected from the radiator. Each time I let it blow out the junk, turn clear, went to hot water, waited until that went clear then back to cold.

Reconnect all hoses and hose clamps. Filled the radiator to the top and started the engine with the heater running. Waited and burped the system until it seemed like it was full then allowed it to cool to see if the level at the cap dropped. Topped it up with another maybe 1/4 cup. Filled the overflow bottle to the FILL line. I used all 50/50 as I sorta guessed I might end up doing this more than once with an engine this old/"oddly" cared for in the past. All in all she took ~3 gallons, which is what I understand to be "full", plus what I put in the overflow bottle.

At no time have there been issues with going over 210F on the dash thermostat and my infrared thermometer backs this up, registering a top temp of 212F.

 

The brown mud in that overflow, has gone through the radiator as well. Good chance that's all gummed up too, God knows what happened by the hands of the PO. Might want to consider clean/new radiator if you're happy it's no longer coming from the block.
And heatercore flushed backwards?
You're not overheating so that's a bonus for now but not sure if you've driven it yet.

 

Except of course when the ship has a masculine name like the USS Teddy Roosevelt. Just don't open the can of worms on whether it's a boat or a ship. :} A Navy architect will tell you that "On a boat the center of gravity is below the freeboard, on a ship it is above. In practice this means a boat, such as a submarine, will lean into a curve when turning while a ship will lean out."

 

Well, I decided here that I was going to just run a bottle of cleaner (citric acid) through the system to see what happens. Gross is the answer.

But now I have a question because something's changed here, or seems to have.

I let the engine cool back down, drained it again, ran some water through it and then attempted to fill the coolant system via the radiator. Put in a bit more than a gallon, start the engine and let it run waiting on the thermostat to open. But instead of taking in more liquid antifreeze/water the car instead gave off a few small bubbles like you'd expect and then blew a ton of liquid back out through the radiator cap at about 170F. Then sucked back in a bit more and spit more back out. It's no longer getting more than about 1.8 gallons of coolant, so far as I can tell but I don't want to keep running it and putting antifreeze all over the ground/risking the engine. Already gonna be a PITA to clean this up.

Ideas?

 

Just checking: Did you do that with the radiator cap on or off?

 

Off. I'm trying to get the car to take more than 1.5-1.8 gallons of anything into the coolant system. It won't. It just spits tons of it back out through the radiator cap port at about 170F.

You can reduce the amount it spits back by holding the throttle to keep the RPM's up but no matter what you do it ends up spitting out a ton of the stuff around 170F then opens the thermostat around 180F and pulls in more.

With water this isn't a huge problem but it makes it kinda a problem to know how much coolant's in the system when you actually go to fill it.

 

Sounds like you have a lotnof air in there. You need to close that off with the cap.
A Lisle funnel works great but assuming you don't have e one, slightly raise the front, fill the radio till full and keep it topped up. But when the engine starts to heat up you need to pit the cap on and allow it to self-burp. Fill the overflow till the fill line.
When no more bubbles appear, shut the engine amd let it cool off. Fill the overflow again till the fill line amd once cool, top the radiator off and put cap back on.

 

parking the vehicle nose up will allow water to rise up and out with the rad cap off, if you leave it overnight. I always do this and have never had a problem with air lock in my vehicles or Jeeps

In the instance where there is lumpy sludge in the coolant, in my opinion, the heater must be back flushed till its clear, the vehicle run with water till it can be drained fairly clear, then the thermostat and radiator replaced

If there is sludge blocking the little hole in the thermostat, that may explain the problems you are having

 

You pretty well covered it. I flushed this thing repeatedly this evening and it's still coughing out stuff if you heat it up. I had cleaned the thermostat and housing when I did the head gasket, as part of deep cleaning the head.

I've had the car at a pretty extreme angle the whole time to try to make the rad cap the high point already, so at this point I've had enough of chasing things down. I'll put a flush kit on it that you hook up to a hose and run it with the rad cap off and flushing in/out cold water until it goes clear tomorrow just to clean the block/heater core. Then I'll replace basically the entire cooling system.

I pulled the trigger on replacing the radiator, thermostat, temp sensor, all the hoses, water pump and just for funzies, the electric rad fan. Parts are, miraculously, all available locally. I'll be picking them up tomorrow morning at 0800 and beginning the block flush as soon as I get back from getting it. I'm not going to chase this down one thing at a time, I'll just do it all in one shot.

Thanks guys, I'll let you know how it goes.

 

The problem was indeed that the radiator was basically shot due to being filled with junk. Inspection after removal indicated that the best treatment for it to be discarded.

I replaced the radiator, electric radiator fan, water pump, thermostat and housing and the temperature sensor along with all the hoses.

After that I was able to put in 2.5 gallons almost immediately with minimal burping and get the rest in via the overflow bottle on the first try. Everything went exactly as you'd want it to (other than having to replace most of the parts in the cooling system).

Test drive of 10 miles varying between 25mph and 65mph went well and the dash now registers 10-25F lower than it did before. Infrared thermometer readings indicate that this is indeed true and not an issue with the new temperature sensor.

Thanks guys!