Coolant will not top off

racertracer · **Posted:** Tue Dec 25, 2012 4:18 pm

Well I can't explain it and I need your help.

Since the coolant in my rig was 7 years old and showing signs of being weak, I decided to drain it today and recovered 2 full gallons.

I drained it using the instructions I received from the Jeep mechanic.... I opened the petcock at the bottom of the radiator and removed the cap on top of the expansion tank. It took some time for the coolant to drain from the small hole but it finally stopped.

I then closed the petcock and began to fill the system with a 50/50 premix of Zerex 05 and distilled water.

I prepared 2 full gallons of the exact amount that came out but the system only took approximately 1.5 gallons, the system didn't take the full 2 gallons.

So I have 1/2 gallon of new premixed coolant left over that will not fit in the cooling system.

This concerns me...the only thing I can think of is trapped air..

Anyone have any ideas?

ChooChooman74 · **Posted:** Tue Dec 25, 2012 6:27 pm

When I did mine, it only took a 1 1/2 gallons. But I probably tolk the zame amount out.

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racertracer · **Posted:** Tue Dec 25, 2012 6:36 pm

Not good.... where is the air?

LMWatBullRun · **Posted:** Tue Dec 25, 2012 7:19 pm

Gravity being what it is, the air is on top. My guess is on the top of the head and or pocketed in some of the tstat hoses, etc. I found mine burped a couple of quarts worth of air when I drained and refilled it to flush the old crap the PO had put in; all I did was add coolant to make up for the air. I suppose if you were really concerned, you could pressurize the system and pump more in......

racertracer · **Posted:** Tue Dec 25, 2012 7:37 pm

I'll try that LMW, but this is starting to sound like my last thermostat change. This is the second time that air is trapped in the head.

Could this problem be the common cause of the head gasket leaks in our CRD?

How many have experienced this? Everyone should measure how much coolant comes out of the system and then measure how much goes in when changing coolant.

I would love to be able to hang the dang thing from it's nose and let the air out of the radiator twist cap on top, that would make me feel a lot better.

And doesn't the thermostat have to reach high operating temperature in order for it to open and then air to escape? This sounds like a dangerous head overheating scenario to me.

I would love to know what VM Motori knows about this or Chrysler....how do they get the air out or do they even know.

The mechanic that replaced the head in my last CRD didn't allow the air to escape he didn't burp it, he didn't have time ... I know because I was waiting for them to complete the work before I drove it away soon after the system was filled with coolant and he said it took about 1.63 gallons.

Three months later I needed the cylinder head and gasket replaced again.

This morning I drained exactly 2 gallons of coolant out of the system.

Not Good.

Does anyone know what the proper procedure to filling the cooling system is?

LMWatBullRun · **Posted:** Tue Dec 25, 2012 8:39 pm

racertracer wrote:

I'll try that LMW, but this is starting to sound like my last thermostat change. This is the second time that air is trapped in the head. Could this problem be the common cause of the head gasket leaks in our CRD?

And doesn't the thermostat have to reach high operating temperature in order for it to open and then air to escape? This sounds like a dangerous head overheating scenario to me.

The mechanic that replaced the head in my last CRD didn't allow the air to escape he didn't burp it, he didn't have time ... I know because I was waiting for them to complete the work before I drove it away soon after the system was filled with coolant and he said it took about 1.63 gallons. This morning I drained exactly 2 gallons of coolant out of the system.

Does anyone know what the proper procedure to filling the cooling system is?

I looked in both FSMs and neither one addresses this, at least not in thr cooling section.

I am going out to look at mine and will report back shortly.

racertracer · **Posted:** Tue Dec 25, 2012 10:09 pm

I opened the plastic twist valve on the top of the radiator to see if any air escaped out ...... no air came out, the coolant came to the top and just sat there at the rim, didn't overflow.

I remember a member back in 2009 drilling and tapping the top of the thermostat and installing a brass twist off relief valve to release the air on top. He was one of the first people that discovered trapped air in the system that had no way to escape. Not many people listened back then, a flush or coolant change was not needed because many CRD's had not reached the coolant replacement maintenance. I'd love to know how he made out but I can't find the thread.

Looking at how the large hose leading from the thermostat to the radiator is shaped, it drops down to the radiator just below the twist off valve..... this can't be right, how can the air escape? it gets trapped on top of the thermostat or in the small hoses maybe.

Anybody?

LMWatBullRun · **Posted:** Tue Dec 25, 2012 10:38 pm

The highest points I see apart from the tank are the heater hoses and the 5/8 hose that crosses over the head right behind the TB housing. If you popped that hose loose you would vent quite a bit of air.... Jacking the front up would help with that.

Another thought is to pull a vacuum on the tank and pull the air out, but I looked at the head, and it has high point dead legs. You might be able to put a jackrabbit drill pump on one of these lines and get some air out that way, too.

I agree with you that this is potentially troublesome. I did not see anywhere in either FSM anything about Coolant flow paths. Anyone know if those are shown for the CRD?

racertracer · **Posted:** Tue Dec 25, 2012 10:49 pm

I am considering splicing the highest most 5/8" radiator hose and installing a Prestone flush and fill hose T. But would that be the proper place to splice it to relieve the trapped air in the head?

Will that trapped air come out from there?

I am thinking that the thermostat needs to open in order to release the air..... meaning the coolant temp needs to reach proper operating temps, what do you think about that?

LMWatBullRun · **Posted:** Tue Dec 25, 2012 11:01 pm

racertracer wrote:

I am considering splicing the highest most 3/8" radiator hose and installing a Prestone flush and fill hose T. But would that be the proper place to splice it to relieve the trapped air in the head?

Will that trapped air come out from there?

I am thinking that the thermostat needs to open in order to release the air..... meaning the coolant temp needs to reach proper operating temps, what do you think about that?

Tstat is probably not airtight. I'd start with that crossover hose, which runs off the stat IIRC, and see how much more you get out. A jackrabbit pump in that hose might do something, too.

racertracer · **Posted:** Tue Dec 25, 2012 11:03 pm

One more thing .... my heater blows hot and cold randomly on its own and the temperature gauge remains constant one or 2 clicks to the left of 12:00. This did not happen prior to the coolant change yesterday.

Not sure what a jack rabbit pump is.

P.S. Never mind I found it "Black & Decker Jack Rabbit™ Pump"

LMWatBullRun · **Posted:** Wed Dec 26, 2012 12:00 am

racertracer wrote:

One more thing .... my heater blows hot and cold randomly on its own and the temperature gauge remains constant one or 2 clicks to the left of 12:00.

The heater blowing hot and cold is a classic symptom of air lock. That could be bad, long term. Makes me glad I put studs in.

racertracer · **Posted:** Wed Dec 26, 2012 7:34 am

This morning I installed a hard plastic Prestone flushing T, at the uppermost 5/8" hose nearest the yellow oil fill cap on the front of the engine where the rubber hose meets the metal tubing.

I noticed that fluid was not draining out when I removed the hose and there was plenty of air in it, nothing was moving out, air or coolant.

I have plenty of fluid in the coolant tank to be able to flow down and fill the air gaps but it just didn't flow out, the 3/8" hose was detached all the way.

I believe that trapped air not being able to escape from the top of this engine maybe the cause to head gasket failures developing over time and soon after a coolant / thermostat change.

There has to be a way to get the air out .... ideas please!

ChooChooman74 · **Posted:** Wed Dec 26, 2012 8:41 am

Random thoughts. 1 is that little hose that comes into the top of the tank... Is that flowing. 2 did you put a new cap on?

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papaindigo · **Posted:** Wed Dec 26, 2012 8:47 am

What I know and what I speculate are largely covered by my posts and links at viewtopic.php?f=5&t=64339&p=711030&hilit=coolant#p711030 .

The bottom line is I think the system capacity is ca. 13.2 qts (I know that's not what the OEM documents say but it's obvious the metric>US conversion is wrong and several things suggest to me the metric figure is correct and the US one is wrong); Squeeto makes it pretty clear (viewtopic.php?f=5&t=56486&p=628305&hilit=citric+flush+acid#p628305) that you cannot drain all the coolant which is obvious given the routing of the lower radiator hose under the drain plug; if you leave the valve on the upper passenger side of the radiator closed during the drain after the coolant tank is empty the drain will be very slow and I suppose it might siphon some fluid out the the engine that would not drain by simple gravity if that valve is open; leaving that valve open and filling from the top of the system (e.g. thru what amounts to the radiator cap on the top of the expansion tank) until fluid starts to come out of the valve and "burping" the upper radiator hose and then closeing the valve and completing the fill from the expansion tank fills the entire system with coolant to at least that level leaving a small bit of air trapped at the top if the system.

On both stoutdog's 06 and my 05 we did the initial refill to about 1" above the midpoint on the expansion tank and did a couple of drive to operating temp and full cool down cycles. That obviously purged all the air as the expansion tank level dropped to the mid point where it has not changed in several thousand miles.

I suspect but have not tried that installation of the Prestone flushing "T" on the highest line (the one running from the viscous heater over the top of the tstat to the heater core) and filling from the coolant tank with the cap off the "T" would purge all air from the system although some hose burping might help.

FYI the heater lines have no valve (doors in the heat/AC unit control whether or not you get heat) and coolant flows in the heater core at all time so doing all this with the heat on makes no difference but I do so anyway.

Inconsistent heat:
1. pull both heater core lines and gently backflush to check for flow and remove debris;
2. if clear could be unpurged air which is not good
3. could also be randomly opening/closing of the doors (bad door actuator system) that directs air flow across the heater core - not sure how to test this but it would cause rising/falling heater output

Is the hose from the gas purge outlet on the tstat to the overflow tank kinked or plugged?

RJM · **Posted:** Wed Dec 26, 2012 9:09 am

I had the same problem when changing the coolant. If you can get some help have a buddy grab the lower rad hose on the drivers side and another the upper hose on the passenger side. rapidly squeeze both hoses together and you will see the trapped air escape into the expansion tank. start drive repeat, start drive repeat. The lower rad hose has a spring in it so squeeze it where it enters the rad. The plumbing system in the CRD is not well designed, there are several areas including the head where air can be trapped. :2cents:

racertracer · **Posted:** Wed Dec 26, 2012 9:23 am

Thanks Pap, I'll check this when I get back later today and read more on your links.

For now, I will be driving it gingerly to work and back to see if the fluid level drops, indicating that air is being purged.

I will see what the Prestone "T" does too, when the thermostat has a chance to warm up. I plan to slowly unscrew it when the engine is hot to see if any air escapes and report back.

Right now the coolant level has remained unchanged, it has not dropped while sitting all night. Yesterday I slowly drove a total of 35 miles after the coolant change allowing the engine to warm up slowly.

I may need to keep driving it as you say and see what happens.

I'll report back.

racertracer · **Posted:** Wed Dec 26, 2012 9:24 am

RJM wrote:

I had the same problem when changing the coolant. If you can get some help have a buddy grab the lower rad hose on the drivers side and another the upper hose on the passenger side. rapidly squeeze both hoses together and you will see the trapped air escape into the expansion tank. start drive repeat, start drive repeat. The lower rad hose has a spring in it so squeeze it where it enters the rad. The plumbing system in the CRD is not well designed, there are several areas including the head where air can be trapped. :2cents:

RJM, thank you .... that may work better, I'll try anything.

racertracer · **Posted:** Wed Dec 26, 2012 11:15 am

All's is good with the world again, the air is out of the system.

When I arrived at work and lifted the hood, the coolant level had dropped. I opened the Prestone "T" and a small amount of air escaped, not significant enough to have made any difference.

But the coolant is at proper level and what ever the hang up was, it is now gone.

What a relief.

I'll be removing the Prestone "T" and reinstalling the stock heater hose back to its proper position, back to stock. It is no longer needed.

ChooChooman74 wrote:

Random thoughts. 1 is that little hose that comes into the top of the tank... Is that flowing. 2 did you put a new cap on?

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ChooChooman, for your info.
1. Yes, the hose was flowing.
2. No, I didn't install a new cap

tjkj2002 · **Posted:** Wed Dec 26, 2012 12:38 pm

Easy way to get air pockets out of cooling systems,works great on any vehicle but Jeeps with the 4.0 I6(why I don't know).........

Install a spill proof funnel(not needed on surge tank systems like the KJ uses).
Fill funnel or surge bottle full of coolant.
Cover radiator will plastic sheet if you have a mechanical fan.
Start engine and run at high idle(1500-2000rpm's) till coolant starts to boil over,shut engine off(will make a mess).
The above forces the trapped air out,as the engine cools the vacuum created will suck in the coolant very fast,be watching and have coolant to poor in when this happens.

Or use one of these,very slick but can be tricky to use sometimes....................
http://www.mactools.com/shoponline/product/tabid/120/p-325646-cooling-system-refiller.aspx

Coolant will not top off

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