99 Ranger 3.0 Engine coolant issues

[tk_427]

I'm completely stumped and so is my local garage. I have a 1999 Ford Ranger XLT 3.0L Flex fuel with only 77k. We can't seem to get the radiator to stop overflowing the reservoir tank. The coolant will go into the overflow tank and not be siphoned back into the radiator. This usually only happens when it is really cold out, below 20 degrees. This also causes a no heat in the cabin of the truck until, what I can only assume is enough pressure or heat from the engine to open up the t-stat and let whatever coolant is left in the radiator circulate into the heater core and then i get heat, really hot heat. I had the thermostat replaced and the radiator because it was rusty inside from sitting for a couple of years with only a few hundred miles being put on it a month (this was my dads truck, and after he passed away it didn't get driven but a few times a week by a neighbor to keep it running)

Once the truck cools down, I can siphone the coolant out of the reservoir about 2/3 of a gallon and open up the radiator cap, and dump it back into the radiator to fill it back up.

The shop has flushed the coolant system 4 times to get the coolant to not look like lake water. They thought that the pressure in the radiator was a little high and that could be caused by a head issue, they have run every diagnostic test to see if the head gasket or head is bad, and it passed everyone. When the weather warms up, it runs fine for a week, but eventually it will overflow again. I'm pretty desperate now. With only 77K on the engine, I would love to keep it running as my dad gently drove it and it is in really great shape.

 

[Curious Hound]

Thermostat should have nothing to do with cabin heat. The coolant should flow to the heater core all the time regardless of thermostat unless the heater hose has a bypass valve.

As far as coolant flowing back to the radiator from the tank, I believe that is a function of the radiator cap. Did you install a new cap with the new radiator?

 

[tk_427]

Yes, new radiator cap installed with the new Radiator.

 

[alwaysFlOoReD]

Also replace the hose from the tank to rad.

 

[tk_427]

i believe that the hose was replaced as well. Could there be an issue with the overflow tank?

 

[Curious Hound]

i believe that the hose was replaced as well. Could there be an issue with the overflow tank?

Only thing I could think of to go wrong there would be if the hose is bottomed out in the tank so that the end is blocked. That might act as a check valve. But it seems very unlikely.

 

[RonD]

Cooling systems are pretty simple so don't over think it

Check the heater hose by-pass valve, its possible for the valve to limit flow thru heater core AND water pump
Pull it off and test it to make sure the valve is not loose inside, long shot but not a no shot

Test system this way:
Cold engine
Remove rad cap
Top it up if its low
Start engine
You may get a burp of coolant out the cap opening but just a burp
let engine idle for 2 minutes
If coolant keeps coming out of rad cap opening then you most likely have a bad head gasket or cracked head issue
Regardless of "test" results, Glove test is what I recommend

A cooling system has say 1 gallon of coolant inside
The water pump is not really a "pump" its a circulator so doesn't increase pressure in the system
So when cold the 1 gallon of coolant just circulates thru the cooling system
None should come out the cap opening


As the coolant heats up it expands in volume, all liquids do, so that 1 gallon becomes 1.25gallons(example) and after 4 or 5 minutes it will start to come out the cap opening, but not before that
The cap is there to hold coolant in until it has expanded enough to pressurize the system to 14psi, this helps increase the boiling point in side the system to prevent overheating

When pressure gets to 15psi cap will open a bit and send HOT coolant over to the overflow tank, but only until pressure is back to 14psi, then cap closes
After engine is shut off, coolant cools down and pressure in the system drops
If any coolant was sent over to the overflow tank then pressure in the system will drop below 0psi because there is no longer 1 gallon of coolant in the system
A smaller valve in the rad cap will be pulled open by the -1psi pressure and SUCK coolant into the rad from the bottom of overflow tank

So pretty simple setup


IF......you have a cylinder leak(head gasket/cracked head) then when you start the engine some of the 900psi pressure from a firing cylinder will go into the cooling system
So INSTANT pressure in the cooling system, and its "air" thats being forced in, and this displaces coolant
So as engine idles coolant would be pushed out of rad cap opening continually
Because air is being forced in it will stay at the top of the cooling system, which is where heater hoses are, so when the air gets into the smaller heater hoses it can cause an "air dam" that blocks coolant flow, causing heat in the cab to go cold, if you REV the engine the water pump can sometimes push the air dam out so heat returns
And the higher pressure and air in the system will cause overflow tank to..............overflow, lol
And when engine cools down the artificial high pressure doesn't go away, so when coolant cools down, so no coolant is SUCKED back in from overflow tank because pressure never drops to -1psi

 

[cbxer55]

Ron always has the longest answers. But the best. Years ago, my sister called me over to her pad due to troubles with her S-10. Sitting there idling, engine cold, the water in the overflow tank was boiling madly. And that's what I told her, either a bad head gasket or a cracked head. Ended up being a cracked head. Also happened to me with a 1993 Toyota four cylinder pickup.

 

[Rearanger]

The overflow tank needs to be vented for coolant to be able to flow back to the rad. Maybe there is a blockage in the reservoir cap vent?

 

[azrangerman85]

I'm completely stumped and so is my local garage. I have a 1999 Ford Ranger XLT 3.0L Flex fuel with only 77k. We can't seem to get the radiator to stop overflowing the reservoir tank. The coolant will go into the overflow tank and not be siphoned back into the radiator. This usually only happens when it is really cold out, below 20 degrees. This also causes a no heat in the cabin of the truck until, what I can only assume is enough pressure or heat from the engine to open up the t-stat and let whatever coolant is left in the radiator circulate into the heater core and then i get heat, really hot heat. I had the thermostat replaced and the radiator because it was rusty inside from sitting for a couple of years with only a few hundred miles being put on it a month (this was my dads truck, and after he passed away it didn't get driven but a few times a week by a neighbor to keep it running)

Once the truck cools down, I can siphone the coolant out of the reservoir about 2/3 of a gallon and open up the radiator cap, and dump it back into the radiator to fill it back up.

The shop has flushed the coolant system 4 times to get the coolant to not look like lake water. They thought that the pressure in the radiator was a little high and that could be caused by a head issue, they have run every diagnostic test to see if the head gasket or head is bad, and it passed everyone. When the weather warms up, it runs fine for a week, but eventually it will overflow again. I'm pretty desperate now. With only 77K on the engine, I would love to keep it running as my dad gently drove it and it is in really great shape.

Pull your spark plugs, check them for fouling from coolant. This sounds like you need a compression test done on your cylinders, it can be a coolant leak internally in your engine that is causing a vacuum issue.

 

[tk_427]

Issue resolved. Even though the glove test proved negative, the shop tried the dye test and this time it came back positive for a blown head gasket, and boy, was it blown! It was blown in 3 spots. 2 of the pistons looked brand new because of the amount of coolant that was flash steaming them clean. Shop replaced the gasket, and the water pump for good measure because that was starting to rust out as well. The truck is running like a champ now!

Thanks to all of you for suggestions, etc.