Coolant expansion tank boiling

[mk378]

Originally Posted By: Emanuel
My coolant gauge IS working, it goes to operating temp when I´m driving in the city traffic but goes to a very low angle when I´m on the highway

That's exactly what to expect running with no thermostat.

Maybe if you go back to that mechanic he has a pile of good thermostats he's taken out of people's cars and he'll give you one.

 

[PeterPolyol]

Originally Posted By: Emanuel

I will look for a tstat, but I had to remove the heater core recently, I put a hose between the heater core ports in the engine, shouldn´t this eliminate any problems with the bypass flow?

If you looped the heater nipples on the engine with straight hose, that would have removed the resistance of the heater core enable even more bypassing! At least close off/pinch the loop you installed until you install a T-stat. Maybe the problem will even go away after that

 

[mk378]

With no thermostat you should close off both the heater loop and the bypass loop so that all the coolant goes through the radiator.

 

[Emanuel]

Originally Posted By: mk378
With no thermostat you should close off both the heater loop and the bypass loop so that all the coolant goes through the radiator.


The hose that I put between both ports is the one that feeded the heater, because of the bend this hose is now blocking the flow, so I have already closed off both ports unwillingly but luckily.

 

[PeterPolyol]

That's good then, but be sure that shutting the heater circuit also shuts off the bypass system- usually systems are designed to bypass regardless of the heater core, because this bypass amount is required to open up the 'inlet side' thermostat which might not otherwise ever open had hot bypass coolant not been washing over it.

It's just very strange that there would be areas hot enough to boil premixed coolant, but not register above-average temperatures on an apparently working gauge......

You do assert that the HG is still good, but bubbles releasing in the expansion tank doesn't add up at all. Any steam generated in the system should push only liquid into the tank, and only because of pressure spikes caused by the immediate boiling. Steam should recondense long before it got to the reservoir. If it's not condensing by then, it might just be combustion gasses. The weird thing with uncontrolled system temperatures is corresponding uncontrolled system pressures. Perhaps there is an intermittent HG leak that is enabled during extended periods of low system temp and pressure, allowing combustion gasses into the system. Then when the system reheats and re-pressurizes like when you pull off the highway and start puttering in hot traffic again, the combustion gasses find themselves at the 'highest point' of the system ie. the rad cap and start to get pushed out into the res. That's all I got for hypothesese right now

 

[Emanuel]

Originally Posted By: PeterPolyol
That's good then, but be sure that shutting the heater circuit also shuts off the bypass system- usually systems are designed to bypass regardless of the heater core, because this bypass amount is required to open up the 'inlet side' thermostat which might not otherwise ever open had hot bypass coolant not been washing over it.

I gotta do research to know that, but it makes sense.

Originally Posted By: PeterPolyol
It's just very strange that there would be areas hot enough to boil premixed coolant, but not register above-average temperatures on an apparently working gauge......

Even in the case of my coolant gauge not working properly my coolant fan switch isn´t working poorly because in that case the car would overheat standing still or in heavy traffic in that case which it isn´t. That´s why I think both my coolant gauge and coolant fan switch are working properly.


Originally Posted By: PeterPolyol
You do assert that the HG is still good, but bubbles releasing in the expansion tank doesn't add up at all. Any steam generated in the system should push only liquid into the tank, and only because of pressure spikes caused by the immediate boiling. Steam should recondense long before it got to the reservoir. If it's not condensing by then, it might just be combustion gasses. The weird thing with uncontrolled system temperatures is corresponding uncontrolled system pressures. Perhaps there is an intermittent HG leak that is enabled during extended periods of low system temp and pressure, allowing combustion gasses into the system. Then when the system reheats and re-pressurizes like when you pull off the highway and start puttering in hot traffic again, the combustion gasses find themselves at the 'highest point' of the system ie. the rad cap and start to get pushed out into the res. That's all I got for hypothesese right now

The main problem are the bubbles in the upper radiator hose, not in the overflow tank. But it is weird that the coolant manages to boil when it is cold according to the coolant gauge. I think that there are in fact hot spots and that the restriction of the tstat is needed to prevent this from spreading.

 

[mk378]

What has checking the radiator every time it is cold found out? If you're losing coolant out of the radiator, is it going into the expansion tank (and not returning), or simply disappearing?

Another test you can do is have the cap on when cold, squeeze the upper hose and feel for pressure inside. (If there is pressure, loosen the cap to release it then replace cap). Then start the engine and rev it while you feel the hose. If you feel pressure building up right away, there's a leak in the head gasket.

The "need restriction" theory is total bollocks. Most industrial systems operate with much faster flow than you'll ever have in a car engine.

 

[Emanuel]

Originally Posted By: mk378
What has checking the radiator every time it is cold found out? If you're losing coolant out of the radiator, is it going into the expansion tank (and not returning), or simply disappearing?

The radiator isn´t full every time I check it, sometimes I have to add 100 cc or less so it comes back to the top. I have noticed that when I add coolant to the radiator to fill to the top after driving the car there is more coolant in the overflow tank so I think the coolant is going to the overflow tank and not returning completely. The problem is that the sometimes the coolant does return to the radiator and it stays full and other times it doesn´t. I might have a faulty radiator cap right?

Originally Posted By: mk378
Another test you can do is have the cap on when cold, squeeze the upper hose and feel for pressure inside. (If there is pressure, loosen the cap to release it then replace cap). Then start the engine and rev it while you feel the hose. If you feel pressure building up right away, there's a leak in the head gasket.

I will do this test it is a good a idea. You can also watch this video putting a funnel on the radiator to check for combustion gases. Testing Head Gasket Problems

The weird thing is that I put a new head gasket a resurfaced the head 14k miles ago, and in the case it was broken it has been that way for more than 3 months, I haven´t seen signs of coolant in the oil or oil in the coolant, and the coolant isn´t dark as it should be if combustion gases were getting into the cooling system.


Originally Posted By: mk378
The "need restriction" theory is total bollocks. Most industrial systems operate with much faster flow than you'll ever have in a car engine.

So my coolant shouldn´t boil without the tsat?

 

[meep]

you missed my post, and another one's above.

You must maintain a higher pressure in the cooling system to prevent boiling at normal temps.

The t-stat regulates temperature, that's all it does. As long as the temp is not topped out, boiling is not a temperature issue. It's a pressure issue.

whether it's a rad cap, or a leak, you don't have enough pressure.

Introduction of forced gases from head gasket failure is also possible. if so, you may find a spark plug with coolant burn debris on it.

 

[zeng]

Originally Posted By: Emanuel
Originally Posted By: zeng
Faulty cap not holding up pressure, OP has no overheating as yet.

I don´t think this is the problem, I have a new radiator cap


Originally Posted By: Emanuel
Originally Posted By: mk378
What has checking the radiator every time it is cold found out? If you're losing coolant out of the radiator, is it going into the expansion tank (and not returning), or simply disappearing?


The radiator isn´t full every time I check it, sometimes I have to add 100 cc or less so it comes back to the top. I have noticed that when I add coolant to the radiator to fill to the top after driving the car there is more coolant in the overflow tank so I think the coolant is going to the overflow tank and not returning completely. The problem is that the sometimes the coolant does return to the radiator and it stays full and other times it doesn´t. I might have a faulty radiator cap right?


How old (in weeks or months) is this 'new' radiator cap ? ...... I mean why and when did you have this 'as is new' cap installed ?

Since you didn't mention any leakage in water pump/hoses/radiator core etc..... and I 'believe' there has to be one, and it's likely the faulty radiator cap.

Note:It occurs to me the video indicates no issue with HG.

 

[mightymousetech]

Originally Posted By: meep

The t-stat regulates temperature, that's all it does. As long as the temp is not topped out, boiling is not a temperature issue. It's a pressure issue.


The thermostat will also increase the pressure in the block. The water pump is pumping against the thermostat, creating a localised pressure increase between the pump and thermostat restriction. Without the thermostat, you get hot spots in the cooling jacket and bubbles form, which can also cause pitting.

I see this all the time at the track. People think they can run without the thermostat and then wonder why they have overheating issues. Put the thermostat back in, or at least put the outer portion of the thermostat back in to provide a restriction, and the overheating/boiling stops.

 

[demarpaint]

Originally Posted By: Emanuel
I have a 01 Corolla with almost 290k miles, it´s thermostat have been removed I know that I should buy and put one again but I can´t afford it and I will stick with the consequences,

Thanks


Good luck let us know what happens. I have a feeling the consequences are going to be a lot more costly than a thermostat.

 

[meep]

Originally Posted By: mightymousetech
Originally Posted By: meep

The t-stat regulates temperature, that's all it does. As long as the temp is not topped out, boiling is not a temperature issue. It's a pressure issue.


The thermostat will also increase the pressure in the block. The water pump is pumping against the thermostat, creating a localised pressure increase between the pump and thermostat restriction. Without the thermostat, you get hot spots in the cooling jacket and bubbles form, which can also cause pitting.

I see this all the time at the track. People think they can run without the thermostat and then wonder why they have overheating issues. Put the thermostat back in, or at least put the outer portion of the thermostat back in to provide a restriction, and the overheating/boiling stops.


That's a good point. I didnt understand it the first time I read that, but it makes sense. It's a restriction that forces the water to distribute throughout the cooling circuit as designed and tested. without it, coolant will automatically rush through the least restrictive passages, and may not flow as readily through others. I can see that - those ignored passages get too hot and you get local boiling. Good point.

-m

 

[Emanuel]

Originally Posted By: zeng
How old (in weeks or months) is this 'new' radiator cap ? ...... I mean why and when did you have this 'as is new' cap installed ?

- Less than 3 months but I don´t trust this radiator cap, I had to modify it in order to be able to use it, I need a new one.

- I replaced it because the previous one wasn´t holding any pressure, this one does hold pressure but I think it has problems with the upper seal and this causes the coolant to not return from the overflow tank into the radiator when the engine is cold.

Originally Posted By: zeng
Note:It occurs to me the video indicates no issue with HG.
Great!

 

[cjcride]

The cooling system has to be sealed, no leaks or the coolant will not be siphoned back into the rad on cool down.

 

[PeterPolyol]

Originally Posted By: mightymousetech

The thermostat will also increase the pressure in the block. The water pump is pumping against the thermostat, creating a localised pressure increase between the pump and thermostat restriction. Without the thermostat, you get hot spots in the cooling jacket and bubbles form, which can also cause pitting.

I see this all the time at the track. People think they can run without the thermostat and then wonder why they have overheating issues. Put the thermostat back in, or at least put the outer portion of the thermostat back in to provide a restriction, and the overheating/boiling stops.


If OP has a 1ZZ Corolla, then his tstat is between the lower rad hose and engine block, instead of between the upper rad hose and cylinder head like on Hondas. It's virtually impossible to affect coolant distribution one way or the other, only bulk flow.

 

[jj51702]

Originally Posted By: OneEyeJack
The thermostat slows the coolant down so that it spends enough time in the radiator to cool down.

Many also control a bypass circuit as suggested above.

Can you use the Internet to get one from Florida? Working out getting one will be cheaper in the long run than paying for the damage in the short run.


Lol, what?

 

[Trav]

Never mind.

 

[Ducked]

Originally Posted By: Emanuel


Originally Posted By: zeng
Note:It occurs to me the video indicates no issue with HG.
Great!


Don't see how that helps you. My understanding was that video isn't your car.

Also, that technique can be difficult to interpret. IF you get a lot of bubbles straight away (he got quite a few), that's either a head gasket or cylinder liner breach or its just trapped air, though there shouldnt be any.

If its trapped air it'll be purged and it'll stop, but by then the system (which obviously isn't pressurised) may have got hot enough for local boiling, which might be indistinguishable from a hg problem.

When I did it, fortunately with a much bigger green funnel I got a lot of expansion but no bubbles for a while, then bubbles as the coolant started to steam from the surface. (didn't have a thermometer but I'll get one if I do it again).

I don't know if these bubbles indicated a hg problem. On the whole I'd think not, but I don't think they excluded a minor/incipient hg problem either.

 

[Ducked]

Originally Posted By: mk378

The "need restriction" theory is total bollocks. Most industrial systems operate with much faster flow than you'll ever have in a car engine.


Yeh, that's a beaut.

I did a bit of googling around to try and find something on the "higher local pressure" thing, which does make some sense, though I'm not sure I believe it with a centrifugal pump.

Didn't find anything on that, but "flows too fast to transfer heat" was pretty much a mantra.

Its the Internyet, y'know?