ANOTHER coolant thread... boiling

[toid]

I have read (literally dozens) of forum threads about coolant boiling.

Mine is little different from the rest of them and I have done most all of what was recommended... Is there anything I am missing?

I have a few questions too.

1990 comanche 4.0 - closed system of course.

It's flippin' HOT here in GA. 90+ (plus the index). Jeep runs 195(ish)-210. Only gets over 210 mark by a sliver if Idling with AC on for longer than a few minutes, but not much over.

Coolant is boiling affter I shut off.

I purchased a new fan clutch. I assume it's working properly but I couldn't tell you for sure, I have read of brand new ones being bad.

coolant and oil both look "normal" and no boiling when running.

I flushed the coolant system twice with parts store prestone flush one afternoon according to the instructions.

AND I have a brand new plastic tank cap (whatever the AP store called "stock" pressure).

I have a new T-stat and gasket but haven't had time to change it yet.

I honestly don't know if I "bled" the air out correctly. I read that I was start cool, uncap the tank, watch for bubbles, fill back what goes down. wash, rinse, repeat unti no bubbles.

Am I missing something? The water pump is flowing / no leaks there and the secondary (elec) fan is doing its thing.

How do I know if my new fan clutch is functioning, and how do I know if I need further burping?

Help would be appreciated.

Rev. Toid

 

Quick edit: It doesn't boil every time, just if I run AC and it gets right there at the 210 mark, and It never loses much coolant when it boils. Maybe 1/4 - 1/3 cup boils out.

[cruiser54]

Put a Napa 703-1396 cap on the bottle. Let us know how it works. 

[danbyrambler]

Your new T Stat should look like # 10 in Cruiser's Tech Pics - They're pinned in DIY - - http://www.cherokeeforum.com/members/cruiser54-42565/albums/jeep-technical-photos/102263-thermostats-2/?gnr_tab=0&ref=gnr-prev   The thing at 12 O'clock's called a jiggle valve - Helps air escape the system - Should be installed that orientation/as pictured - A hole that size can be made in your's if it doesn't have one.

 

Boiling coolant in an engine with air trapped inna head or too low system pressure will make a peculiar sound when shut off - Don't know exactly how to describe it - a popping/cracking/banging/tapping noise kinda - Lasts for a min or so usually - You'll know it if/when you hear it 

[nitroxsteve]

Pressurizing the system raises the boiling point of the coolant. If its boiling that tells me your cooling system is not holding pressure.

[cruiser54]

Pressurizing the system raises the boiling point of the coolant. If its boiling that tells me your cooling system is not holding pressure.

Yes. And the crappo chinese caps we get now don't fit the bottles well at all.

 

The 703-1396 caps fit well, even on crappo bottles. 

[toid]

Of course my tstat ain't got no jiggle valve. What size is that hole?

[toid]

I am assuming that because none of my hoses are leaking that they are holding pressure.

but I have owned enough Ford products to know that just because it makes sense does not make it true.

[toid]

OK

Ok

I cannot blame this one on Cheap Chinese rad caps.

Unless the caps that are labeled, "Motorad Germany" are Chinese as well. I changed my tstat. When I took off my coolant tank cap the pressure piece inside the threaded cap part came apart and the threads on the cap would barely grab the tank and would not hold under even slight pressure when I tried to screw it down. I ordered a new one this am and will have it installed by lunch tomorrow.

I drilled 2 holes in the tstat at 12/6 as suggested. No bubbles nor such in or around tank when I started and ran it up to operating temp. Water level rose a bit but tank didn't drain back down when it cooled.

[toid]

OK.

Got it done.

As Cruiser requested... Here's the update.

I replaced the tstat as I said last time. I put the Napa cap on the bottle. Nice fit. I pressure washed my fins up front to make sure airflow is good. Had a cooler week last week and today was the first scorcher we had. Ran to town with AC blasting. Temp got to 210 -a sliver over the mark actually. Pulled in the driveway and after about 45 seconds a slight boiling began. It carried on for less than 4 mins and lost less than a full cup of coolant. Heard a slight pressure sound... Couldn't tell if it was sucking or blowing but it was where the heater hose branches to the bottle. First time I noticed that hose hissing. There was water dripping from the tank cap but none visably discernable from the hose.

By the quality advice I received here, my logic tells me to check/replace these hoses. If not a fix, then I burn my truck to the ground and dance around it like a wild Indian. (No offense to our native american members)

Any other advice?

Rev. Toid

[95wrangler]

Burp the system again.I lift the rear of the truck untill the rear of the engine is higher than the front, Remove the cap from the bottle. Remove the temp sending unit/switch watch for coolent to escape. Then replace the unit/switch.Drive the truck repeat, If need-be.

[cruiser54]

If that green Napa cap doesn't seal you may have to replace the bottle. 

[toid]

Ok. Any favorite bottle selection... Or is it a stealership-only item?

[toid]

I may be experiencing ignorance here.

Is the cap supposed to totally seal the bottle or isn't it designed to seal up to a particular level of pressure at which point steam/ fluid is allowed to bleed off? If a bad hose is allowing depressurization which causes boiling and the resultant steam, shouldn't I expect the cap to vent the risen steam/water to prevent something from rupturing?

[toid]

I could very well be stupid. Its not unusual. So please correct me if I'm not seeing it right.

[cruiser54]

That green cap releases at 16 PSI when it seals good on the tank. 

 

I'm thinking the tank may be too far gone, and you've got issues with the heater hoses. 

[toid]

Tank referral? I will do all hoses n clamps at same time as the tank and a good burping.

[cruiser54]

Napa. They're all from the same supplier any more anyway. Napa has a lifetime guarantee. I write the replacement date on the bottle with a Sharpie. 

[toid]

More and more. She always wants more.

Oh well, At least she not a Ford.

[reprod89]

when the last time you check the flow of the radatior ot see if it not cloged up the simple test is to flush with a gallon of water at the top and see how long it reaches bottem if it not free flowing thares your porblem

[Eagle]

Is the cap supposed to totally seal the bottle or isn't it designed to seal up to a particular level of pressure at which point steam/ fluid is allowed to bleed off? If a bad hose is allowing depressurization which causes boiling and the resultant steam, shouldn't I expect the cap to vent the risen steam/water to prevent something from rupturing?

No. The plastic bottle is a pressure bottle. Nothing should escape or "bleed out." To prevent rupturing the bottle under pressure, the bottle is filled to the halfway mark when the system is cold. The air in the bottle compresses under heat, allowing the coolant to expand.

 

How high are you filling the bottle? If you have been filling it -- there's your problem.

[toid]

I haven't "filled" it, but I did fill it a bit beyond half. Now that u mention it, after the boiling and the overflowing, I ran it up to temp and parked a few times (I only live a mile or so from work) my coolant level is is at "half full bottle".

I'm really considering a cooling conversion. This is aggravating.

I flushed the system with off the shelf prestone product twice and the water flowing out of the radiator hose didn't seem restricted to me. When I changed the tstat, the water jacket behind the tstat on the head and tstat housing looked really good so I imagine the radiator passages were cleaned well enough. But I'm no pro in that area.

Rev. Toid

[tugalo]

Replaced my bottle with a really sturdy one from a mid-90's Mopar.  Made of thick nylon and has a real radiator cap.  has a slightly different shape than OEM bottle, but easily installs once you remove the OEM bottle and mounting bracket...

[toid]

@Tugalo: could you provide me with some details on the bottle? what model vehicle or some details that I can use to find what you have. also did you use a 16 pound radiator cap or whatever radiator cap came with the bottle?

[Exgrayxj]

Maybe you are already doing this, but if not,  when you have the radiator cap that Cruiser recommended (Volvo cap) it will be a press fit into the neck of the tank. Sort of an interference fit, before the threads connect, then tighten it on.  The factory one, dealer one  and ALL available replacement stock type (black "knurled" grip) are junk, and will lose their grip on the threads of the tank. The Volvo one won't.

 

There is a "post" in the tank, directly below the neck, and the cold coolant level is at the "notch" in the post, over fill it and it will probably push some out.

 

Park the truck on an incline, front down, so that the rear of the cylinder head is higher than the front, remove the temp sender, this will bleed air trapped in the head. Re install it when burping stops, it won't take long.

 

Run a fan shroud. Make sure the fan clutch is good.

 

On my 2 (LT1 powered XJ and stock MJ) I got a later model (I prefer the 97 up, but I think the twisted blades started in ~95)  electric fan, there seems to be several blade counts, got mine from the u pull, the plug will probably be wrong so get both halves of the plug.

 

With a 160 tstat and an aluminum radiator, my LT1xj runs at 185, in traffic it goes up a little, so then I turn the A/C on, to kick on both fans, cools right back down ...

 

On the xj I modified the stock plastic tank to be my resevoir, gutted the stock cap, and it usually keeps about 1/2-3/4" cold level coolant in the tank, more at first shut off, then drops to that level cold.

 

With a 190 tstat, your gauge reading will probably be at ~210  normally.

 

Hope some of this helps, maybe you don't really have a problem, just over filled.

[toid]

Do I burp via the temp sensor with it running?