Burping the radiator
 

Ok, I am going nuts here. I have had air in my coolant system for almost a year now and I CANNOT get it out.

Replaced Alternator and had to drain the coolant last year. Filled back up ran it for 15 minutes after bubbles stopped I put the cap on. I knew I still had bubbles because sometimes the truck would read fully heated when I first turned it on.

I tried many many things since then.

Installed a T flush in top most heater hose to fill from highest point.

Flushed it 2 more times.

Got a BIG funnel so I could stick in the rad filler hole and over fill

Finally this week I decided I needed a new radiator anyway so I got a new radiator, hoses, dual stage t-stat (replaced the other OEM that was only 6 months old)

Did my air purge when I was done using the large funnel and ran the engine for 1 FULL hour. Let it cool off and now... I STILL HAVE AIR IN IT.

You can hear it slosh when you squeeze on the upper rad hose.

by the way the truck has NEVER gotten over the half way mark on the temp gauge. Sometimes it shoots right up to fully heated after 10 secs, but has never gone past.



Please, what am I doing wrong. :pop:

I have heard if you elevate the front of the vehicle... say on an incline or jack... that it may burp stubborn air.

do a 3.4 swap :laugh:

I'm pretty close :nono:


I have already tried bleading it on a ramp... puts the front end about 2.5 feet higher than the back. Didn't get any results, just ran for 45 minutes and no air ever came up.

Is it possible you have a small leak somewhere?

Do you have the factory style thermostat installed? It has a little jiggle valve that goes towards the top. Helps with passing air through. Also...are you doing all this with the heater fully on? If not air will get trapped in the heater core. Do you have a new rad cap? Try replacing that as well. If that's not sealing properly it will just suck in air instead of from the overflow bottle.

Take off the rad cap. Turn the heater on and start the truck. Squeeze the upper rad hose and pour water as it's needed. After awhile shut off the truck, put the rad cap back on and pour some water into the overflow bottle. This has always worked for me.

That's all I can think of at the moment. I've never had a problem with my 3.0 in that respect.

Good luck
Jason

Hmm...my 85's temp guage has always hopped to the "warm" mark about 45 seconds after starting. Did that since the day I got it, and also after I replaced the alternator (which as stated requires draining the radiator). I just figured it was an old design flaw or something. Perhaps I too have always had air trapped in there? Never have seen any adverse effects...

Think I might have to do as stated to try and get some air out.

Anybody else's temp guage move that fast?

Pest....read this:http://www.4crawler.com/4x4/CheapTri...tml#Thermostat

I'm going to assume that is why linux has a "dual stage" thermo in his.

Awesome, perfect answer. Thanks thook, and thanks 4Crawler, once again your site is extremely helpful.

do you have the heat on when you "burp" the truck.?

heat must be on full

Yup, heat is on full

I got a dual stage thermo to avoid temp overshoot. Thanks Yotatech :banger:


I am pretty sure i don't have any leaks...

Let me get this straight. Your truck is not overheating and you want to do something about it? Is that right?

:D YEP... remember i have been living with this air bubble for a year, so it's not like i didn't try to ignore it.

I tend to be a little picky about things working the way they were designed, and the coolant system was not designed to run with air in it.

Pretty sure is not the same as definite, though.:hillbill: Any small leak even unnoticed will introduce air into the system. There are places where leaks can occur wherein the spilled fluid wouldn't be readily visible. I had a small one (that eventually led to a large one...spew!) at one of the small coolant lines down and in between the valve cover and intake plenum....right around the thermo housing. The line had gotten very soft and cracked until one day it actually burst. I've also had leaks at the heater hoses running to the core wherein the coolant ran in through the firewall and under the carpeting. Wasn't enough to smell it with the windows down....as at the time it was warm weather. So, if the air in the system is really a concern, just closely inspect all coolant lines great and small. Also, where the cold start time switch and temp sensor mount.

Oh, and check the heater hose where it connects at the side of the block. And maybe you just have a loose clamp somewhere.

you have to turn it upside down to burp it.

With gentle patting on the back, eh? :barf:

Might sound stupid/obvious, but have you disconnected the upper hose at the radiator and poured coolant straight into the hose? Always works for me.

My cooling system acted weird until I removed the u-shaped hose from the sensor bank (the bypass hose) on the back of the engine.

I put my rose gun (oil sucker/pusher thing) on it and sucked coolant hard out of both sides of that passage. I think it sucked an rtv booger up into the rose gun, but can't say for sure.

Anyway, I replaced that hose, then removed a heater hose or some other "high" connection, filled from the radiator until coolant was flowing out the high point, and reconnected the high point while coolant was still flowing out.

That was it. Now my runner acts normal.

Before that, I had tried all the burp tricks with no success.

Also, I may be wrong, but I never knew that a little air in the upper radiator hose (the big hose) was "bad". All my life, i have checked coolant level by removing the cap and seeing if the vanes were "just covered". There is always a bit of air in the top of the radiator.

Burping is to alleviate an air pocket trapped at a high spot somewhere else in the system. If you have trapped air in the "rear" of the system, it can airlock, preventing proper flow throughout the entire system. However, I've never been told that a little air in the "front" of the system necessarily leads to an airlock somewhere else.

This is just my understanding of how it works. Mebbe I've been wrong for years and someone will point that out. mebbe not.


In most radiators, the absolute top of the vessel is higher than the cap outlet. It would be virtually impossible to get all the air out of the radiator itself.

Your thoughts?

Ok, Update...

I double checked all of my heater hoses (the only hoses left that have not been replaced) and they look good.

I may have noticed something tho...
Previous owner removed a heater cable; it switches the valve open/closed to allow coolant in to the heater core. They removed the cable and pushed the valve open. I am still able to change between hot/cold via the in-cab controls, so I never noticed. I think the removed cable was the bright blue one. Any idea if this could make a difference?

Well, that's what I've always noticed, too. So, I believe you're correct on that. The main thing anyone has to concern themselves with it is air pockets trapped somewhere midstream in the waterjackets or heater core, etc. creating hotspots. If the coolant flows through the top of the rad without large bubbles popping CONSISTENTLY or causing the thermostat to hang up, then nothing to worry about. You have to consider, if the coolant level was ever to get really low there would be air in the top hose period, but still no hotspots or thermo hang up is created because (hypothetically) there are no trapped air pockets in the system. The only problem there is the lack of enough coolant to properly dissipate heat.

The control cable (the blue one) being broken or remove is nothing to worry about, unless when you are servicing the coolant system and burping it the heater valve is not open when you think it is....going by the control shifter. I don't see how you are able to switch from hot to cold if that cable is disconnected. Telekenesis? The cable on my '86 had been broken for a long time. So, everytime I have to service it, or come winter so I have heat, I have to open the valve under the hood. Sure I can't control the heater temp, but I can control the fan and heat output. So, I ain't worried about it.:D