Dodge Ram overheated then started knocking........

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byez

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I believe it was a leak in the coolant overflow reservoir which caused it to overheat. The thermostat & rad cap were recently changed. Had to drive the truck and thought I would just take things slow and that it would not overheat. My mistake.

So the truck overheated and now when I start the truck I hear a loud knocking. Could it just be that the oil has thinned? What part is most likely to fail in overheating conditions? I'll try to get an audio/video clip up.
 
There is a possibility that the oil failed to protect due to extreme heat, and is just shot and needs a change ASAP, that is what I would do. There is also the possibility that the bearings were damaged as a result of the high temps from over heating and oil failure, and that's where the knock is coming from. Try swapping the oil and filter and see.

What oil were you using and how long/miles was it in? Either way good luck!

Frank D
 
Why would a leak in the overflow tank cause the truck to overheat? Years ago cars didn't even have overflow tanks.

Coolant or lack of coolant in the radiator is what would cause the truck to overheat.

Wait a minute I just read the other thread. From your discription it doesn't sound like the white plastic overflow tank is leaking. If it were leaking up next to the top, no coolant would leak out of the overflow tank, level in the overflow tank is never more than about 50%. From your discription it sounds to me like you had a leak in the top tank on the radiator itself.

And you got to ask if you should drive it or not? HOLY MOLY!

How hot did you get the truck?

The needle went up and idiot light came on and you shut it down, let it cool off, RIGHT!

or

You kept driving the thing, thinking it ain't going to get too hot? With no coolant in it!!!!!!

When you shut it down did you hear remaining coolant in the engine flashing off?

Okay let's review the basics. The engine in your truck requires lubrication and cooling. Lubrication comes from oil, oil in the engine is good- no oil bad. Cooling comes from water/coolant in the radiator,radiator full good - radiator empty bad.

Can you drive a truck with no coolant in the radiator- yes, but not very far as you have discovered yourself.
 
People just so you know if you ever run out of coolant you can always make to safety by doing the following. As soon as the coolant lose happens shut off the engine. After is is cool drive one mile shut down and let it cool, drive one mile shut down let it cool until you reach help. Now mind you I am talking about a situation where you are in a remote location. If you are with 5-10 miles of help and are a non-disabled adult male you should just walk!
 
Quote:
Why would a leak in the overflow tank cause the truck to overheat?


Easy. The overflow tank and cap rating allow the purging of air from the system. It's an expansion tank that's at atmospheric pressure. You heat up ..push expanded coolant and/or purged air into the tank ..the engine cools and sucks back in only liquid. No liquid ..it sucks back only air. Add a few too many heating cooling cycles ..and viola~ ..over heated engine. The same thing would happen with an older system with a bad cap gasket.
 
You probably have a rod knock, now.
Change your oil, and possibly go to a little thicker grade.
See how she reacts.
After that, you need to put n bearing shells [absolute minimum].
 
Originally Posted By: Gary Allan
Quote:
Why would a leak in the overflow tank cause the truck to overheat?


Easy. The overflow tank and cap rating allow the purging of air from the system. It's an expansion tank that's at atmospheric pressure. You heat up ..push expanded coolant and/or purged air into the tank ..the engine cools and sucks back in only liquid. No liquid ..it sucks back only air. Add a few too many heating cooling cycles ..and viola~ ..over heated engine. The same thing would happen with an older system with a bad cap gasket.


That's an excellent explanation Gary.
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Originally Posted By: Gary Allan
Quote:
Why would a leak in the overflow tank cause the truck to overheat?


Easy. The overflow tank and cap rating allow the purging of air from the system. It's an expansion tank that's at atmospheric pressure. You heat up ..push expanded coolant and/or purged air into the tank ..the engine cools and sucks back in only liquid. No liquid ..it sucks back only air. Add a few too many heating cooling cycles ..and viola~ ..over heated engine. The same thing would happen with an older system with a bad cap gasket.


Okay!

I went back and read both the original post where he describes the leak and his original post here where he describes the overheat problem on the truck.

Question remains why would a leak in the overflow tank cause the truck to overheat? He describes the leak as being at the top of the overflow tank. If it is indeed the overflow tank that is leaking, the level of coolant in the overflow tank never gets to the top. Secondly even if you remove the overflow tank and the coolant is then vented to ground on each heat cycle, it would take several if not numerous heat cycles to actually get the coolant level down to the point where the truck might overheats. Any one knowing the overflow tank is leaking would know to check coolant level everyday right? You know first thing in the morning top it off with water and let it rip. You could probably drive several days before you need worry about the water level. Besides that wouldn't the coolant in the radiator reach a point where it no longer expanded enough to need to vent to the expansion tank. Somewhere in the process you reach an balance.

Yesterday I found the rubber fill tube between the radiator and expansion tank unhooked, how long? I have no idea, Lord only knows how many heat cycles, could have been ten- might have been fifty, One thing I do know, my truck has not overheated- not once- in south La. heat. The coolant level in the radiator wasn't even low.

However: If as he describes his leak is at the top of the expansion tank next to the radiator cap.
"Its around the plastic that the rad cap sits but it is not the rad cap which is leaking or the rad cap's seal. The hole is in the actual plastic tank."
Now that sounds to me like the top tank on the radiator itself was/is leaking. We all know you ain't going far like that, and that will cause the truck to overheat. Within a few minutes or miles. As you drive along you constantly spew coolant out of the leak, not just the coolant that goes to the expansion tank due to the heat cycle.

That is what I think happened.

By the way I have a Dodge truck I will go look at the radiator cap, expansion tank and such, but I think he busted his radiator not the expansion tank.
 
Originally Posted By: JohnBrowning
People just so you know if you ever run out of coolant you can always make to safety by doing the following. As soon as the coolant lose happens shut off the engine. After is is cool drive one mile shut down and let it cool, drive one mile shut down let it cool until you reach help. Now mind you I am talking about a situation where you are in a remote location. If you are with 5-10 miles of help and are a non-disabled adult male you should just walk!


JB, the current ford 6 cylinders sold in Oz have a coolant free limp home mode. Alternately allows fuel to cylinders, and apparently 50km or so is OK...must rely on the air flow through the non fueled cylinders to carry away heat.
 
Regardless of the proper name for it, over flow tank, expansion tank, if it was designed to hold pressure and couldn't because of a hole, then the cooling system would be boiling water off at 212'. Every time the engine was shut off , it would boil over and lose coolant. Do this for a week or 2.........
 
Originally Posted By: andyd
Regardless of the proper name for it, over flow tank, expansion tank, if it was designed to hold pressure and couldn't because of a hole, then the cooling system would be boiling water off at 212'. Every time the engine was shut off , it would boil over and lose coolant. Do this for a week or 2.........


I don't think my expansion tank will hold pressure. It is vented at the top to atmosphere.

Hose comes out of radiator, goes into the expansion tank through the center of the expansion tank cap. Hose hooked to the inside of the cap goes down to the bottom of the tank. So when coolant flows out of radiator because of heat cycle, it will draw it self back in when the engine is shut off. The vacuum created inside of the radiator as it cools off draws the coolant back into the radiator.

No way will that tank hold pressure. Heck it's made out of white/clear poly plastic.

However you bring up a good point. Water boils at 212*, an engine can run at 212* without damage. So if you remove your rad cap water temp will stay at 212* and you can get home, as long as you don't boil off all the water.
 
Quote:
He describes the leak as being at the top of the overflow tank.


The same effect occurs if you have a leaking hose at the fitting to the tank.

Quote:
Yesterday I found the rubber fill tube between the radiator and expansion tank unhooked, how long? I have no idea, Lord only knows how many heat cycles, could have been ten- might have been fifty, One thing I do know, my truck has not overheated- not once- in south La. heat. The coolant level in the radiator wasn't even low.


Call Ripley's or audition for the next Dos Equis commercial (j/k
grin2.gif
)

Quote:
Secondly even if you remove the overflow tank and the coolant is then vented to ground on each heat cycle, it would take several if not numerous heat cycles to actually get the coolant level down to the point where the truck might overheats.


Much depends on cooling system capacity ..load...service duty cycling (stop=go=cruise, hills ..flatland ..etc.).

Quote:
Any one knowing the overflow tank is leaking would know to check coolant level everyday right?


Suppose it was full? Suppose the hose connection was the only leak?

What we're probably missing is exactly where the coolant was leaking from. Coolant recovery tanks have overflows in them. They also may have connections near the top (most that I've seen, anyway).

Now he could have already had a head gasket leak. Depending on how severe, he may initially produce bubbles into the system and push coolant out of the coolant recovery tank. As the engine warmed and cooling system pressure increased, this can be reduced and/or eliminated (it "depends").

I've just gone through this with my 91 3.0 Vulcan ..and my son's 96 2.0 SOHC Neon.
 
Originally Posted By: andyd
Regardless of the proper name for it, over flow tank, expansion tank, if it was designed to hold pressure and couldn't because of a hole, then the cooling system would be boiling water off at 212'. Every time the engine was shut off , it would boil over and lose coolant. Do this for a week or 2.........


That is not necessarily correct. There are a number of different types of cooling systems in use. Almost all of them are pressurized, but WHERE that pressure is restricted is a function of the type of system.

Three examples:

1. Old-school 8psi-style systems found on 60's and 70's cars. Many of these did NOT have overflow tanks. There was always some sort of air in the cooling system. Yet they functioned fine. They typically had larger rads, and copious quantities of under-hood space that allowed for much better heat dissipation than the modern cramped engine compartments which rely VERY heavily on an efficient cooling system.

2. Newer systems with a non-pressurized overflow. The system found on all older Ford automobiles for example. My Town Car, Mustang, Explorer (1997)...etc all had this system. The pressure cap (15psi for the Lincoln for example) is on the radiator. The overflow tank simply has a clip on cap. There is a level of coolant in this tank and two lines indicating full cold and full hot. As the coolant expands, it eventually overcomes the 15psi limit of the cap on the radiator, causing the expanded coolant to exit the radiator into the overflow container and increasing the level to the "full hot" mark. When the car is shut off, and the coolant cools (and contracts), the negative pressure inside the radiator draws back in the coolant from the overflow and brings it back down to the "full cold" mark.

3. Pressurized overflow. My dad's 03 Town car has this, my mom's 2000 Expedition has this system. There is no rad cap. The cap is instead a screw-on cap on the actual overflow container. This container is opaque plastic and has the same "full cold" and "full hot" marks as the older system, except the pressure in the system is controlled by the cap on the actual overflow.


And a couple of points:

- Ethylene Glycol has a higher boiling point than water (198C). A 50/50 mix of traditional green antifreeze (Ethylene Glycol) and water NOT pressurized has a boiling point of 107.2C (225F).

- Pressurized coolant has a higher boiling point than non-pressurized coolant. So while a 50/50 mix of EG and water will boil at 225F, under 15psi, water boils at 250F, and with a 50/50 of EG, boils at 265F.
 
Originally Posted By: Shannow
JB, the current ford 6 cylinders sold in Oz have a coolant free limp home mode. Alternately allows fuel to cylinders, and apparently 50km or so is OK...must rely on the air flow through the non fueled cylinders to carry away heat.

Fords get this over here too. I know my Vic has it, and so does my Dad's 1999 4.2L V6 F150. They call it "fail-safe cooling". It uses a temperature sensor in the back of one of the heads to determine temperature. At one set point it will alternate cylinders, and restricting it to below 3000RPM to try to keep the engine cool. At another higher point it will shut off fuel entirely to save the engine. When activated it will also light up the instrument cluster like a Christmas tree.
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Pressurized expansion tank on the 4.7L, okay that explains it. Excuse me I had made the assumption the cooling system was the same as the Hemi. Then a leak in the pressurized portion of your coolant system whether it be in the radiator or expansion tank, would be the same. As the engine came up to temp and the coolant system built pressure the leak would constantly spew coolant. Ain't going far like that.

Yes! I am aware of the properties of saturated steam, and I do understand that water under pressure boils/steams at a higher temp. I guess I left out the part about leaving the rad cap off, that way the system will not pressurize. But the water/coolant will boil away pretty fast.
 
That's unfortunate, those 4.7's are pretty tough. But overheating any engine is the work thing you can do.....
 
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