Coolant not flowing?

[shmicah]

99 XJ 4.0L

I recently replaced the entire cooling system: new CSZ radiator, gates water pump, thermostats & thermostat housing, overflow bottle, and hoses

I hooked everything up, and poured about 2 gallons distilled water into the radiator cap.

Started it up and let it sit for a few minutes. Coolant didnt seem to be flowing, I stopped the jeep and the manifold was freakin hot!

Started it again, and this time coolant just started bubbling out of the radiator cap.

I've started and stopped it several times now, and let it run for several minutes.

-The temp gauge seemed stuck at 1/4, yet the engine bay feels fully heated.
-Turned the heater on full blast and it was cold air.
-The upper radiator hose is not warm, and I don't feel anything flowing through


Is it likely the t-stat is stuck closed? Is it possible an air bubble is causing the tstat to stay open, and to not move the gauge past 1/4?

 

[Tim_MN]

Have you filled the cooling system to the 10.5 quart capacity ?

What the the manifold or engine bay "feels like" is irrelevant. The thermostat will not open until the coolant reaches the proper temperature. The coolant may not flow properly until the system is mostly full. The heater core will not give heat until it has purged any air and is full of 195* fluid.


When servicing the cooling system, fill the radiator and leave the cap off. Start the engine and keep filling the radiator as the level drops slightly. When the thermostat opens, usually there is a small burp of air and/or coolant, then put the radiator cap on. The open cooling system is self burping, all you have to do is monitor the coolant level for a few days

 

[ParadiseXJ]

99 XJ 4.0L

2 gallons distilled water into the radiator cap.

Started it up and let it sit for a few minutes. Coolant didnt seem to be flowing, I stopped the jeep and the manifold was freakin hot!

Is it likely the t-stat is stuck closed? Is it possible an air bubble is causing the tstat to stay open, and to not move the gauge past 1/4?

Capacity for the cooling system is right around 12 quarts (3 gallons). If it's not full enough, coolant will never even reach the thermostat to open it or register correctly on the sender.

The manifold and the cooling system are separate systems. It'll get HOT whether you have coolant in it or not.

Are you just running water??

 

[shmicah]

Thanks for quick response yall.

I poured 2 gallons (8 quarts) distilled water only (no coolant) into the radiator through cap. I did not fill while running it the first time, but did later. I bet I let it pull more air in.

When I let the engine really run, and coolant started coming out of cap, it was hot and smoking/boiling a bit. So that makes me believe it is circulating...

I guess I will try with even more fluid. I will also put the front on jacks to be sure.

"Are you just running water?"
Yes, the intention was to run just water for a day or two then flush and refill. It's pretty brown.

 

[8Mud]

A partially plugged radiator can cause issues, one tip off is the large top inlet radiator hose swells and gets so hard you can't squeeze it together.

 

[alexgalexg]

You may have a faulty radiator. I did not see you say anything about replacing the cap. It could just be that the cap is overdue for replacement thus the coolant flowing out of it.

 

[Tim_MN]

... recently replaced the entire cooling system: new CSZ radiator, gates water pump, thermostats & thermostat housing, overflow bottle, and hoses

:dunno:

 

[RCP Phx]

-Turned the heater on full blast and it was cold air.

Yes, the intention was to run just water for a day or two then flush and refill. It's pretty brown.

You may have a clogged heater core!(which affects flow while the stat is closed)

If it's brown you've been a bad boy!

 

[shmicah]

You may have a faulty radiator. I did not see you say anything about replacing the cap. It could just be that the cap is overdue for replacement thus the coolant flowing out of it.

It's a new radiator so hopefully not. I did bump it against the clutch drive and crush some fins in about a square inch area, but nothing serious and its not leaking. I should have been more specific, when the coolant was flowing out of the cap area, the cap was off. Once I put the cap on, coolant started flowing into overflow bottle.

A partially plugged radiator can cause issues, one tip off is the large top inlet radiator hose swells and gets so hard you can't squeeze it together.

The large inlet radiator hose on RHD side is not swollen, and does not even seem to be warming up. I can also squish it and don't feel anything going through.

You may have a clogged heater core!(which affects flow while the stat is closed)

If it's brown you've been a bad boy!

Yes I have A solid 15 years of using tap water. Also, when I had it disassembled, I tried to flush with vinegar, then ran water hose through it to flush everything out. then it sat for a good 2 months and I'm sure it is now disgusting in there. :twak:

My understanding though is that the heater core is in parallel with the rest of the cooling system, so even if my heater core is clogged it won't affect anything else - I just won't get heat.

I'm picking up a bunch of distilled and gonna give it another go tonight.

Approximately how long should it take for the coolant to start pulling into the radiator? I am nervous about waiting too long and overheating.

 

[RCP Phx]

My point was that the heater core provides flow when the t-stat is closed allowing circulation thru the radiator regardless of the heater control.
I just buy the pre-mixed coolant anymore!

 

[shmicah]

My point was that the heater core provides flow when the t-stat is closed allowing circulation thru the radiator regardless of the heater control.
I just buy the pre-mixed coolant anymore!

Oh, so if heater core is clogged (very likely) then I won't have flow through the radiator until the tstat opens.

 

[shmicah]

Ok, just tried it again. Still no luck, here's what happened.

-Jacked front of jeep up a few inches
-Removed radiator cap and filled port with distilled water until full
-started jeep and waited for water to be drawn into the system
-after about a minute, I can see a few bubbles but wter level not moving
-begins bubbling faster, about 1-2 bubbles a minute, but water not going anywhere
-after ~2 minutes, I can see water slowly swirling
-water level starts increasing and trickling OUT of the radiator port (still no cap)
-within 20-30 seconds the water flow leaving radiator increases and begins pouring out of radiator
-water seems hot as I see vapor
-I put the cap on and it just pushes water into the reservoir tank
-water was brown, temps still 160 so shut it off.

During this time, the jeep did the following:
-Temp ramped normally to 160, then stayed there (googling points to stuck open tstat)
-interior heater never got hot (likely expected given low temp?)
-top radiator hose was cool, and did not feel under pressure
-lower radiator hose was warm, was not pinched (I have no spring in my new Gates hose)
-RHD side of radiator feels cool, LHD side is warm
-upper heater hose was warm
-lower heater hose felt cool
-I turned AC on and fan would not engage (could this have any impact on tstat position?)

Why would water be pushed up OUT of the radiator? If the tstat was stuck open as my low temps lead me to believe, I would expect water to pull into the radiator. If water starts coming out of the radiator, does that mean I should put radiator cap on, and it will push into the reservoir bottle until it reaches a "steady state", then begin to circulate as normal? A clogged radiator wouldn't push water up out of the cap, right?

I'm debating on if I should pull tstat and roll into the driveway then flush everything individually with water hose, or get the prestone flush n fill kit? Will a prestone flush n fill kit only work if coolant is actually moving through the system?

 

[md21722]

Changing the radiator doesn't require 10-12 quarts to be added. You'll never get all the coolant out. What do you NEED to do it let the AIR out. When filling, I always remove the upper radiator hose at the thermostat when filling. When I see the coolant rise in the neck, I put the hose back on and dump about 2 quarts in expansion jug. After a few cycles, it drops about 1 quart. Then I top off the expansion jug as needed. 8 quarts is a pretty good though. I would try again making sure the upper radiator hose is disconnected. Some people park on a hill, jack the front end up, etc. I find it easier just to disconnect the upper rad hose at the t-stat block.

 

[shmicah]

Changing the radiator doesn't require 10-12 quarts to be added. You'll never get all the coolant out. What do you NEED to do it let the AIR out. When filling, I always remove the upper radiator hose at the thermostat when filling. When I see the coolant rise in the neck, I put the hose back on and dump about 2 quarts in expansion jug. After a few cycles, it drops about 1 quart. Then I top off the expansion jug as needed.

Remove upper radiator hose at thermostat, and fill radiator through that hose until I see water coming out of radiator neck where the cap would be? Then do you put radiator cap back on before running system or run it with cap off?

 

[md21722]

I just stick a big funnel where the radiator cap goes and fill it that way. Seems to be the least messy way to do it for me. You can also pour into the hose or not use a funnel. It's all going to the same place, straight into the radiator where the engine fills from the bottom up and air escapes through the thermostat. I watch the level at the thermostat housing (where you removed the hose). When it starts to rise put the hose back on and call it good. Dump 2 quarts or so in the expansion jug. The system can naturally purge some air, but not tons of it. I used to try to get crafty with dumping straight distilled and then straight coolant. Anymore I just premix and dump 50/50 distilled/green in there until it won't take anymore. I've seen pockets of air do just as you describe, the top of the engine is super hot, and the temp gauge doesn't read it...

Please let us know how this turns out.

 

[shmicah]

Thanks for the help md! I am up and running

I jacked the front end up more than I did before. I pulled top radiator hose and filled radiator until full at the cap (I could hear some air seeping out of top radiator hose). I also filled thermostat housing from top radiator hose side. I reconnected hoses and then squeezed the shit out of the lower radiator hose and got a LOT of air to bubble out of radiator neck that way.

Turned it back on and ran until water started flowing out of radiator again, then put the rad cap on. It is now working perfectly. Temp stabilized at 210 and heater is blowing warm (enough) air.

Unfortuantely, efan is not kicking on but at least it is driveable. Tomorrow I'm gonna roll it into the driveway and give it a hardcore flush via prestone flush n fill kit, then give it a couple of fill/flush cycles with distilled water before a final fill with distilled/coolant.

 

[md21722]

Glad to hear, but there's another problem.. running straight distilled water will cause your block and head to rust... don't leave it this way for very long at all... Mix 50/50.

 

[shmicah]

good to know, I thought distilled wouldn't rust since it is mineral-free.

Either way, tomorrow I am giving it a flush and finishing with a mix.

 

[md21722]

Straight water would be better for what you're doing... I've seen what distilled water can do too! because it has no minerals of its own it wants to suck everything it can. That's why you mix it with coolant but never run it by itself.