Coolant System Issue

[Deppdog]

I have a 1992 Ranger with a 4.0. It recently started overflowing coolant out of the overflow reservoir. I haven't had to do anything with the cooling system for quite some time, so no new components. I did have to top off the radiator a week ago with maybe a quart into the reservoir. Hadn't checked it in quite some time, so I'm not sure how long it took to go down. Seemed to do fine right after that until a week later when the overflowing began.

Here are the symptoms and things I have checked:

A.) No noticeable oil in the water or water in the oil.
B.) Overflow reservoir and hose are free flowing - no clogs.
C.) Overflow reservoir will not drain back to radiator.
D.) Top and bottom hoses sometimes collapse after parking & cooling down.
E.) Occasional small bubbles viewed in overflow tank as coolant flows in.
F.) No known or noticeable leaks in cooling system.
G.) Does not overheat - stays in Normal range but temp gauge does
fluctuate significantly and suddenly within the Normal range.
H.) Noticed that hoses sometimes collapse while running and the temp goes
up. If I rev the engine or speed up the temp will go down and hoses will
expand back to normal. Seems like a lack of coolant at the time
when the hoses are collapsed.
I.) Heater works fine.
J. With radiator cap off and at operating temperature, coolant will blurp out
from the filler and will continue to do so until it gets a couple of inches
down. You can still see it blurping at the lower level.

Any help would be greatly appreciated!!! Thanks in advance!!!

 

[BRUTUS_T_HOG]

get a new radiator cap. and a new thermostat.

don't worry about the overflow being full. just have the radiator full and the overflow at the proper cold fill level AFTER you bleed the air from the cooling system.

a lever vent radiator cap helps with bleeding, i park upwards on a steep hill and bleed like that.

is there and coolant smell or white smoke coming out of the exhaust pipe?

 

[Deppdog]

Nope...no coolant smell, except for when it spills over. No white smoke either. I was thinking radiator cap and thermostat for a place to start. Thanks!

 

[Big Jim M]

A.) No noticeable oil in the water or water in the oil.
B.) Overflow reservoir and hose are free flowing - no clogs.
C.) Overflow reservoir will not drain back to radiator.
D.) Top and bottom hoses sometimes collapse after parking & cooling down.
E.) Occasional small bubbles viewed in overflow tank as coolant flows in.
F.) No known or noticeable leaks in cooling system.
G.) Does not overheat - stays in Normal range but temp gauge does
fluctuate significantly and suddenly within the Normal range.
H.) Noticed that hoses sometimes collapse while running and the temp goes
up. If I rev the engine or speed up the temp will go down and hoses will
expand back to normal. Seems like a lack of coolant at the time
when the hoses are collapsed.
I.) Heater works fine.
J. With radiator cap off and at operating temperature, coolant will blurp out
from the filler and will continue to do so until it gets a couple of inches
down. You can still see it blurping at the lower level.

I'm thinking a compression leak into the coolant.. I'd be filling it to the top of the radiator and if when ruinning you see bubbles, them are from the compression leak..
I betcha you need not only a thermostat and radiator cap but also a coolant pump and head gasket kit.

When you put that quart in the coolant tank did you LOOK into the radiator? Was it low? Sounds to me like you have a slow outside leak and the heads got low on coolant and overheated the gasket...maybe the heads themselves...let's hope not.
Big Jim

 

[Deppdog]

Well, tried a new thermostat and cap. Burped the system and the problem is still occurring. Still no visible signs of a head gasket issue such water in the oil or oil in the water. I suppose I should pressure test the radiator and do a leak down test. Any other ideas?

Thanks!

 

[Big Jim M]

Well, tried a new thermostat and cap. Burped the system and the problem is still occurring. Still no visible signs of a head gasket issue such water in the oil or oil in the water. I suppose I should pressure test the radiator and do a leak down test. Any other ideas?

Thanks!

What you need to KNOW is the compression pressure is far greater than the coolant pressure! A leak in a head gasket usually results in compression gasses blowing bubbles into the coolant passages.. This excess pressure causes the radiator to have more than the 16lb the cap will allow. Then the cap opens to vent the excess pressure and out comes the coolant...
So to see if you have a head gasket leak..
Park with the radiator cap slightly higher than the rest of the coolant system. Take the cap off (carefully) and fill to the brim with water.
then start the engine. While the engine is running watch the coolant in thebrim of the filling inlet. If bubbles, small ones usually, start coming out then you have a compression leak.
Many times while the engine is running it may become necessary to have a water hose with a small trickle of water to KEEP the coolant lever up in the neck of the fill area. If the coolant level drops below the fill hole it is impossible to see all the bubbles.
This is really easy to do..
Big JIm

 

[Deppdog]

Thanks Big Jim! I'll make this my project for Saturday morning.

 

[BRUTUS_T_HOG]

also take a sniff at the filler neck. if it smells like exhaust/oil then you've got a bad head gasket or cracked block/heads

 

[Deppdog]

I tried Big Jim's idea for checking for bubbles, and nothing showed up. No bubbles in the overflow tank either. Also, checked the plugs and no coolant visible. No coolant in oil or oil in coolant. Pressure tested the radiator with a pump tester. It did leak down, but very slowly. The coolant has stopped overflowing and the system is full...but BIG air pockets keep forming in the top hose. Somewhere there is air coming into the system. Could it be from a tiny radiator leak? I mean sometimes the whole top hose feels like it is mostly air and you can feel coolant blurping through, and sometimes the hoses will collapse! I did put a new cap & thermostat in, but this problem was occurring before that. I am baffled! Any ideas? Thanks!

 

[BRUTUS_T_HOG]

so the pressure leaks down.. find the leak