Bubbling in Radiator?

[TCruiser93]

I have bubbling in my radiator after an average drive. The coolant in the reservoir has decreased slowly. I have replaced my fan clutch, thermostat, radiator, hoses and had a pressure test done to check for other leaks, so by all accounts no leaks and HG should hopefully be ok although I know it's possibly hurting. Any ideas would be greatly appreciated! Thanks!

 

[BILT4ME]

I have bubbling in my radiator after an average drive. The coolant in the reservoir has decreased slowly. I have replaced my fan clutch, thermostat, radiator, hoses and had a pressure test done to check for other leaks, so by all accounts no leaks and HG should hopefully be ok although I know it's possibly hurting. Any ideas would be greatly appreciated! Thanks!

Regular coolant loss is only by a leak or a HG.

It took me 3 months of regular checking to find my coolant loss and it turned out to be the 3 o-rings on the bypass pipe by the thermostat.
I happened to catch a bit of coolant before it evaporated to define where the leak was occurring.

I cleaned that up and installed new o-rings and all new hoses, including the PHH and rear heater hoses.

Then it opened a leak on my 8 YO OEM radiator. That's the last part in my system now.

You may encounter similar things in tracking a coolant loss.

If you cover all these bases, then check the radiator for exhaust gases.
Then a compression test on each cylinder.

 

[landcrshr]

I have bubbling in my radiator after an average drive.

What does this mean exactly? Are you hearing bubbling after you shut the engine off? Or are you actually seeing bubbles while it's running?

 

[Dirt Ferguson]

Is the hose from your radiator to your burp bottle fully secure and without any cracks? Is your burp bottle cracked?

 

[SpenserAK]

Would also suggest doing a combustion gas test as mentioned, as well as closely running through all the lines & connections to search for a leak.

Do you have a scangauge or equivalent to see true temperature?

 

[TCruiser93]

Regular coolant loss is only by a leak or a HG.

It took me 3 months of regular checking to find my coolant loss and it turned out to be the 3 o-rings on the bypass pipe by the thermostat.
I happened to catch a bit of coolant before it evaporated to define where the leak was occurring.

I cleaned that up and installed new o-rings and all new hoses, including the PHH and rear heater hoses.

Then it opened a leak on my 8 YO OEM radiator. That's the last part in my system now.

You may encounter similar things in tracking a coolant loss.

If you cover all these bases, then check the radiator for exhaust gases.
Then a compression test on each cylinder.

I had a leak in the little radiator bypass hose, think that's what was called. Why I replaced it. What is the PHH and does that have something to do coolant loss?

 

[TCruiser93]

What does this mean exactly? Are you hearing bubbling after you shut the engine off? Or are you actually seeing bubbles while it's running?

Hearing bubbling after shutting off the motor

 

[TCruiser93]

Is the hose from your radiator to your burp bottle fully secure and without any cracks? Is your burp bottle cracked?

I believe that's all good

 

[TCruiser93]

Would also suggest doing a combustion gas test as mentioned, as well as closely running through all the lines & connections to search for a leak.

Do you have a scangauge or equivalent to see true temperature?

Why would a compression or combustion if that's the same thing tell me about a coolant/bubbling issue? I do have temp gun...what temp should it be?

 

[flintknapper]

Why would a compression or combustion if that's the same thing tell me about a coolant/bubbling issue? I do have temp gun...what temp should it be?

Tyler first....we are trying to differentiate between 'Bubbling' (bubbles SEEN in the radiator with cap off , engine at idle, upon first start up) and 'overheating' which is the coolant 'Boiling'.

A combustion gas test is performed by attaching a special chambered tube to the radiator (where the radiator cap would go). You fill the tube partially with a solution that changes colors if exhaust gases are present in the coolant. IF the solution changes color that indicates a head gasket failure (to some degree).

Exhaust gases from the cylinder would be getting into the cooling system. This would manifest as 'bubbles' in the coolant, over pressure of the cooling system and overheating.

On the other hand.....if you have 'boiling' of the coolant in the radiator, that can be caused by a number of things. It would also result in coolant loss since the expanding coolant is forced into your overflow reservoir and lost there (once full).

If your dash gauge works (temp gauge)....it should be indicating an overheat condition if your coolant is so hot that it is boiling.

Now as for troubleshooting this, there are a couple things you can do right away that might give you some direction.

First, with a Cold Engine, remove the radiator cap, check to see that your coolant level is correct (just below the neck of the filler). Start the engine then look down into the radiator and watch for 'bubbles' (they will be constant very distinct if present). Let the engine reach operating temperature (thermostat open). IF no bubbles, breath a sigh of relief and we can move on to the cooling system itself.

There is no way the cooling system should be hot enough to 'boil' at current temps (Central Texas) I am sure you know.

Can you give us a little history as to why the components replaced (radiator, t-stat, hoses, can clutch, etc) were replaced? Suspected leaks.....or overheating? If a cooling pressure test was performed and no leaks found that helps eliminate certain possibilities.

You asked what normal cooling system temps should be. I wouldn't want to see anything over 205°F this time of year in your area, no matter the driving conditions. If you are in the Kyle, Buda, San Marcos area (or Austin east of the lakes) its not like you are pushing your cruiser hard on any of the hills. Boiling temp would be North of 240°F with 50/50 mix of water/antifreeze and properly working radiator cap (around 13 psi).

You can check for high temps with your IR gun. But lets first define what the issue IS (is it bubbles or is it boiling)?

 

[robnicko]

it may be worth checking the water pump. How clean is the coolant? possible the water pump fins could be plugged up with gunk if red & green coolants have ever been mixed and therefore not pushing the coolant properly which will result in it boiling.
Also unbolt the fan shroud and have a good look down the sides of the radiator for leakage that may dry up and never show a drip on the ground - my original radiator did this and was allowing air into the system.

 

[BILT4ME]

I had a leak in the little radiator bypass hose, think that's what was called. Why I replaced it. What is the PHH and does that have something to do coolant loss?

The PHH is the "pesky heater hose" that is located on the left rear of the engine, down low, just above the starter.
It is known to fail from the inside out. It can start as an annoying coolant loss because you can never find it because a cool engine may not drip because the hose does not relieve enough to leak when cold. It may only leak a little when hot but not enough to drip. The coolant may blow off or evaporate when hot.

Then, over time, it decides to blow out catastrophically and it is a difficult change out on the side of the road.

So, most do this as PM preventive maintenance. It takes most about 2-1/2 hours to change this hose.

Do a search on PHH and you'll find many threads and images of it.


The bubbling in a radiator after shut down can be normal due to heat soak after an engine is shut down. The coolant closest to the cylinder tends to boil because it is no longer circulating. The bubbles find their way to the highest point and that is in the radiator. As long as the system remains closed, and the system cools down, the vapor condenses back into liquid and it all stabilizes.

So, the overflow tank level should rise as the engine warms up, the coolant expands, and it pushes out to the tank. When the engine is shut off, the sudden increase in temperature will cause more coolant to be pushed to the tank.
Then as the entire engine cools, and the fluid contracts, the negative pressure sucks coolant back in from the tank, this, keeping the radiator full with no air pockets.
If there is a leak, the system is no longer sealed and as it cools it will continue to draw coolant from the tank and eventually the level in the tank will be low.

That's why you check levels when cool.

Checking combustion gases in the cooling system checks to see if there are exhaust gases in the coolant causing the bubbles. This is a direct correlation of a blown head gasket.

A compression test will confirm is there is a weak cylinder, which could be a blown head gasket, a bad valve, or broken rings.

This is why it's important to do PROPER diagnosis when something is amiss.
Many folks shoot the parts cannon at the truck hoping that they guessed right the first time, only to continue to do it until resources are exhausted and frustration levels are high. Then they sell the truck because it's too expensive and then people likee buy it for a song, do a proper diagnosis, change out a $10 part and drive it for two more years.

 

[TCruiser93]

Thank y'all for the replies so far! Sorry I've been so busy with this and other things, I'm just now getting back to reading them.

 

[TCruiser93]

Tyler first....we are trying to differentiate between 'Bubbling' (bubbles SEEN in the radiator with cap off , engine at idle, upon first start up) and 'overheating' which is the coolant 'Boiling'.

A combustion gas test is performed by attaching a special chambered tube to the radiator (where the radiator cap would go). You fill the tube partially with a solution that changes colors if exhaust gases are present in the coolant. IF the solution changes color that indicates a head gasket failure (to some degree).

Exhaust gases from the cylinder would be getting into the cooling system. This would manifest as 'bubbles' in the coolant, over pressure of the cooling system and overheating.

On the other hand.....if you have 'boiling' of the coolant in the radiator, that can be caused by a number of things. It would also result in coolant loss since the expanding coolant is forced into your overflow reservoir and lost there (once full).

If your dash gauge works (temp gauge)....it should be indicating an overheat condition if your coolant is so hot that it is boiling.

Now as for troubleshooting this, there are a couple things you can do right away that might give you some direction.

First, with a Cold Engine, remove the radiator cap, check to see that your coolant level is correct (just below the neck of the filler). Start the engine then look down into the radiator and watch for 'bubbles' (they will be constant very distinct if present). Let the engine reach operating temperature (thermostat open). IF no bubbles, breath a sigh of relief and we can move on to the cooling system itself.

There is no way the cooling system should be hot enough to 'boil' at current temps (Central Texas) I am sure you know.

Can you give us a little history as to why the components replaced (radiator, t-stat, hoses, can clutch, etc) were replaced? Suspected leaks.....or overheating? If a cooling pressure test was performed and no leaks found that helps eliminate certain possibilities.

You asked what normal cooling system temps should be. I wouldn't want to see anything over 205°F this time of year in your area, no matter the driving conditions. If you are in the Kyle, Buda, San Marcos area (or Austin east of the lakes) its not like you are pushing your cruiser hard on any of the hills. Boiling temp would be North of 240°F with 50/50 mix of water/antifreeze and properly working radiator cap (around 13 psi).

You can check for high temps with your IR gun. But lets first define what the issue IS (is it bubbles or is it boiling)?

Let me double check on the bubbling vs boiling thing and I will get back with you on that. Thanks! I had the radiator replaced because of a small leak, t-stat cause I assumed could be an issue, hoses just with radiator, fan clutch assuming overheating issue again. I have over 280K so I'm not totally opposed to replacing things just to see.

 

[TCruiser93]

it may be worth checking the water pump. How clean is the coolant? possible the water pump fins could be plugged up with gunk if red & green coolants have ever been mixed and therefore not pushing the coolant properly which will result in it boiling.
Also unbolt the fan shroud and have a good look down the sides of the radiator for leakage that may dry up and never show a drip on the ground - my original radiator did this and was allowing air into the system.

Idk about the water pump but my mechanic told me it looks good and things seem to be flowing. My radiator and coolant is brand new so doubt that's an issue.

 

[TCruiser93]

The PHH is the "pesky heater hose" that is located on the left rear of the engine, down low, just above the starter.
It is known to fail from the inside out. It can start as an annoying coolant loss because you can never find it because a cool engine may not drip because the hose does not relieve enough to leak when cold. It may only leak a little when hot but not enough to drip. The coolant may blow off or evaporate when hot.

Then, over time, it decides to blow out catastrophically and it is a difficult change out on the side of the road.

So, most do this as PM preventive maintenance. It takes most about 2-1/2 hours to change this hose.

Do a search on PHH and you'll find many threads and images of it.


The bubbling in a radiator after shut down can be normal due to heat soak after an engine is shut down. The coolant closest to the cylinder tends to boil because it is no longer circulating. The bubbles find their way to the highest point and that is in the radiator. As long as the system remains closed, and the system cools down, the vapor condenses back into liquid and it all stabilizes.

So, the overflow tank level should rise as the engine warms up, the coolant expands, and it pushes out to the tank. When the engine is shut off, the sudden increase in temperature will cause more coolant to be pushed to the tank.
Then as the entire engine cools, and the fluid contracts, the negative pressure sucks coolant back in from the tank, this, keeping the radiator full with no air pockets.
If there is a leak, the system is no longer sealed and as it cools it will continue to draw coolant from the tank and eventually the level in the tank will be low.

That's why you check levels when cool.

Checking combustion gases in the cooling system checks to see if there are exhaust gases in the coolant causing the bubbles. This is a direct correlation of a blown head gasket.

A compression test will confirm is there is a weak cylinder, which could be a blown head gasket, a bad valve, or broken rings.

This is why it's important to do PROPER diagnosis when something is amiss.
Many folks shoot the parts cannon at the truck hoping that they guessed right the first time, only to continue to do it until resources are exhausted and frustration levels are high. Then they sell the truck because it's too expensive and then people likee buy it for a song, do a proper diagnosis, change out a $10 part and drive it for two more years.

I've never know about the PHH, that's interesting. And maybe I will see about a compression test. Thanks!

 

[shylock]

I have bubbling in my radiator after an average drive. The coolant in the reservoir has decreased slowly. I have replaced my fan clutch, thermostat, radiator, hoses and had a pressure test done to check for other leaks, so by all accounts no leaks and HG should hopefully be ok although I know it's possibly hurting. Any ideas would be greatly appreciated! Thanks!

 

[Kernal]

@TCruiser93 : If you could, please answer these few questions:

Do you actually see coolant bubbling out of your radiator or overflow tank?

Or, are you just hearing bubbling/gurgling when sitting inside the vehicle?

 

[TCruiser93]

@TCruiser93 : If you could, please answer these few questions:

Do you actually see coolant bubbling out of your radiator or overflow tank?

Or, are you just hearing bubbling/gurgling when sitting inside the vehicle?

Well I’ve been checking again. I’m not seeing coolant bubbling in the overflow. I hear it from inside the vehicle after I shut off the motor. I can also hear it with the hood open if I get out quick enough to listen.

 

[flintknapper]

Well I’ve been checking again. I’m not seeing coolant bubbling in the overflow. I hear it from inside the vehicle after I shut off the motor. I can also hear it with the hood open if I get out quick enough to listen.

Tyler, is your dash temp gauge showing an elevated temperature when this happens (as with an overheating engine).

Did you check for bubbles in the RADIATOR with the cap off (engine cold upon start up)?

When you are driving....are you running your A/C then parking and turning engine off (and then hearing the under hood noise)?

I ask because I wonder if you are hearing the 'normal' noise of the high and low side of the A/C system 'equalizing' after shut down.