I didn’t think of it until you mentioned it. But even then, the sensor is submerged, in coolant, if coolant gets hot, sensor should read it hot, unless I missing something (which I probably do because I am only a backyard mechanic).

 

1. I mentioned in post #3 you may have a leaking cap. I realize a cracked bottle is not EXACTLY the same thing, but it DOES the same thing. Posting ALL the information possible is how you get people to devote their valuable time in helping you.

Again, asking questions is how we give the best help - it gets everyone thinking about all the possibilities. If the degas bottle does not pressure up, it will not properly heat up in temperature, but it should read up to the boiling point of the coolant fluid (which depends on the coolant type and concentration you have). Also, temperature probes will not work as accurately when in 2 phase fluids.

2. The only way your cooling system can have air in it is if the level ever dropped significantly from coolant loss. If this hasn't happened, your coolant system has no air in it. If GAS is escaping from the crack in the bottle, it is boiling water OR it is combustion gas - say from a head gasket. If it isn't combustion gases, then you are losing coolant fluid - maybe only a little, maybe only water, but you are losing some.

3. Seems like you got an answer on your probe since you state it is submerged OR, are you assuming it is submerged because there is a good liquid level in the degas bottle? Maybe you have a temperature gauge (digital cooking thermometers work well) that you can put in the liquid in the degas bottle to see what it reads? Make sure everything has heated up and circulated so you can compare apples to apples.

I am only posting this to "help you get help", so please - take it for what its worth.

 

Please confirm the location of the temp sensor.

 

The cooling system is a closed unit. Water boils at atmospheric pressure in an open system. In the closed system with increased pressure, the water will boil at a higher temperature which is how engines are designed to run at a designed temperature without boiling the water. Therefore, if the system looses pressure (such as a defective radiator cap, pressure leak, etc.) the water will boil without a higher temperature reading. Just my two.

 

Not to be a smart ***, but for the beginner like me, you made more sense then anyone above, even though their info is helpful, but you just cleared it up for me.

 

The thing you have to consider is that even though water boils at 212 deg F (atm pressure), antifreeze mixtures boil at over 300 deg F at atmospheric pressure. For your fluid to boil at atmospheric pressure and 212 deg F (or close to it), it would have to be all water and almost no antifreeze. Assuming you have 50/50 antifreeze, even if you have a pressure leak (cap, bottle, whatever), at atmospheric pressure you will still see the the elevated temperatures on your temperature gauge if your engine is overheating and if your gauge is working.

If you don't understand the help you are given, just say so. With the information you have given in your posts (again assuming you have an antifreeze/water mix), it appears you do still have an overheating problem or an exhaust gas leak into your coolant - even though this is not the question you are asking. Your engine begins to defuel at 227 degrees, normal operating range is 190 to 210. This is not a big window to see problems with the rather poor OEM sensor and gauge.

 

pull your egr and see if it is wet if it is wet if it is your gonna need and egr cooler and while your there replace the oil cooler also

 

I'd get that reservoir replaced as well. That seems to be the main issue that is abnormal so I'd start with that. If the crack was OK then there would be no need for a closed pressurized cooling system.

Its kinda like saying.....my engine makes a funny noise....but only when there is no oil in it??????

 

will start with that this coming weak.
Will keep you udated.
thank you all for your help.

 

Actually, with no pressure on the system, specific parts of the heads CAN easily exceed 300 degrees F, and boil even pure (non-diluted) coolant. Pressure and flow normally keeps the coolant moving so that it has insufficient time to actually reach the 300+ degrees required for boiling at the hot spots.

The drop in pressure allows several things to happen. One is that the spinning water pump impeller can generate low-pressure boiling; the inlet pressure can be below atmospheric for a short distance in the pump inlet, and so the coolant can boil. That leads to interruptions in coolant flow (and usually fairly fast water pump failure).

Another "pressure" failure is that the low pressure/flow can allow hot spots to form permanently, and this lets the normal "nucleate" boiling to quickly accelerate to full-out boiling. (nucleate boiling is a normal function - tiny bubbles of steam forming and quickly being re-absorbed as liquid by the cooler surrounding water - and it actually allows for faster heat transfer to the coolant.)

In any case, the take-home point here is that the cracked reservoir is preventing normal cooling system pressure from working properly. Replace it and it should solve most of the overheating issues.

-blaine

 

Frankenbiker -

From what you have posted, isn't "lower-than-design coolant flow" an essential component of both of the boiling examples you gave? That being the case, doesn't it condense by the time it reaches the degas bottle in the recirculation flow?

As you said, the water pump will not last long (and you will hear it) in the low suction pressure cavitation mode you described. IIRC antifreeze is dense enough that it is hard to get the low suction pressure boiling - even w/ no back pressure unless you have HIGH flow rates and / or actual HIGH suction temp situations. (has been a long time since looking at VLE for ethylene glycol)

(good write-up btw)

 

No. The Degas bottle isn't part of a circuit (as far as I know). It's a dead-end branch at the topmost part of the coolant loop. So the only time the degas bottle sees coolant flow is if there's something pushing it out the top -- either entrained air (from a refill) or combustion gasses and/or steam (from blown gaskets or other failure).

I haven't looked at it CLOSELY, but in principle it's similar to the top tank on my Freightliner. On it, there's a SMALL bypass flow into the top tank, so that any additives that are put in (as are needed in the Freightliner from time to time) are mixed into the normal coolant loop. But this is a tiny flow, on the order of maybe a pint per minute.

Low-suction-pressure boiling doesn't take that much of a drop in pressure when the temps are that close to boiling in the first place. Additionally, the water pump on these it moving several 10's of gallons per minute. (The above mentioned Freightliner's Detroit Series 60 will move as much as 160 GPM at full-blast.)

As an example, when I used to haul salt-water in the oilfield, putting a 20-inches-of-water vacuum on 160-180-degree saltwater would have the whole trailer boiling, and you could feel the whole truck bounce from the bubble action. And that's on a steel-sprung Mack RD680.

A water pump in cavitation won't have THAT much of a pressure drop, but it will be either close to 212 or even over it, and at that temperature, you could use soda-straw suction to boil the coolant.

-blaine

 

I haven't looked at it closely, I was just thinking about my coolant filter that returns to the degas bottle - it has constant flow. I guess it was dead-end until I installed the filter - just hadn't thought about it.