Boiling in Degas Reservoir but coolant is 210 F.

AmsterDutch

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I'm going to be doing a coolant system rebuild ...I seen my degas reservoir boiling today when I opened the hood to check my coolant level...funny thing is Forscan is reading my Engine coolant at 95 C. -210 F. ...when I put the heater/defrost on my coolant starts to boil ...when I turn it off the coolant stops boiling...when the coolant is boiling the temp reads 95 Celsius ...when coolant isn't boiling it reas 95 Celsius ....strange system in this 2002 LSE 3.9 ...whatever the case may be looks like I'm going for a rebuild ...I've done it a few times ...FWIW ...the degas cap barley hisses when I take it off hot...has to be air getting in the system
 
Is the cap holding pressure at all? Squeeze the upper radiator hose on the engine when it is boiling. Is it hard or is it too soft? It could be the cap. You have to pressurize the system to raise the boiling point, and that could be all there is to the problem. I just had the same thing happen to my lady's Subaru WRX. The hose was not getting even close to firm, and it was boiling at normal temps. A new cap solved it.
 
Is the cap holding pressure at all? Squeeze the upper radiator hose on the engine when it is boiling. Is it hard or is it too soft? It could be the cap. You have to pressurize the system to raise the boiling point, and that could be all there is to the problem. I just had the same thing happen to my lady's Subaru WRX. The hose was not getting even close to firm, and it was boiling at normal temps. A new cap solved it.
Funny you say that ....the previous owner has a aftermarket cap on the degas reservoir...I was thinking that might be a good idea to try a new cap ...being it's a 2002 once it started to boil my first instinct was to change out all plastic I may as well just order a whole new degas reservoir and give it a shot before I dive into a full rebuild ...it wouldn't hurt giving it some more flushes anyway due to th he previous owner using Dex-Cool
 
The cap by itself is a pretty easy find, mine for my LS came from Advance Auto Parts 4 years ago, still working well!
 
Squeeze the upper radiator hose on the engine when it is boiling. Is it hard or is it too soft?
The hose seems kinda soft I think...not really sure though ...not an expert in cooling systems by any means...just know boiling coolant = problems in the system = change the plastic coolant parts...How hard or soft should the upper radiator hose be?
 
The cap by itself is a pretty easy find, mine for my LS came from Advance Auto Parts 4 years ago, still working well!
The simple answer to this question is that the boiling point of water is 100 C or 212 F
of course the the boiling point of water depends on the atmospheric pressure, which changes according to elevation. The point I'm trying to get at is I flushed the entire system twice with distilled water until water was the only thing coming out ....could it be that the water to coolant ratio is greater than it really should be ...because even today the highest temperature I was reading on Forscan was 96 celsius?
 
You could try pressurizing the cooling system while cold... and see if it holds pressure. If it drops quickly... you probably have a leak that you might be able to hear and locate.

All you need is a cooling system pressure tester.
 
You could try pressurizing the cooling system while cold... and see if it holds pressure. If it drops quickly... you probably have a leak that you might be able to hear and locate.

All you need is a cooling system pressure tester.
UPDATE: I changed out the Degas Reservoir Cap today ...The car's temperature is a steady 95 celsius and the coolant once again only starts to boil upon turning on the climate control... this is so weird ...coolant system rebuild here I come
 
There is a difference between boiling... and bubbling. If it is happening only when you turn on the heat... your DCCV might be cracked be and/or sucking air. Possibly the "quick connect" hoses to/from the DCCV... that attach to the aluminum tubes that run along the passenger shock tower. There are O-rings in there. Worst case... the heater core.

Pressure test the cooling system cold... and see if it holds. If not... get some U/V dye... and a black light... and check it while hot. There's gotta be a leak somewhere.
 
Pressure test the cooling system cold... and see if it holds.

I haven't tried it, but I wonder if a vacuum test wouldn't serve us better for these problems?
Okay 04' Sport ... I will pressure test the system cold ...going to purchase the OEMTOOLS 24444 5 Adapter ...I need something like this and the price looks fair
 
There is a difference between boiling... and bubbling. If it is happening only when you turn on the heat... your DCCV might be cracked be and/or sucking air. Possibly the "quick connect" hoses to/from the DCCV...
I think you're onto something here the Dual Climate Control isn't working.... when I try to set a different temp on passenger side...the digital numbers only decrease and increase at the same time with the driver side arrow...of course If I the pressure test shows I have a leak I planned on changing it out anyway of course ...thinking I should do the radiator and water pump also since I'm in there
 
...when I try to set a different temp on passenger side...the digital numbers only decrease and increase at the same time with the driver side arrow...

That would be an internal fault of the DATC (never seen that one, though), and not anything related to any faults of the DCCV.
 
That would be an internal fault of the DATC (never seen that one, though), and not anything related to any faults of the DCCV.
Wasn't sure if that was an internal fault or the valve itself ...I was leaning towards an electronic fault in the DATC panel but my wishful thinking brought me to hoping it was something in the valve itself...could it be a blown fuse of any kind?
 
In theory it could work... but not sure how a leak would be found.

Unless you mean for just working the air out of the system???

You would identify that there is indeed a leak by watching the vacuum drop after you turn it off. You may be able to locate the leak by sound using a mechanic's stethoscope.
 
Dutch - going to recommend you consider what fixed very similar problem for me, after replacing several other things - that expensive little hydraulic fan actuator.
 
Dutch - going to recommend you consider what fixed very similar problem for me, after replacing several other things - that expensive little hydraulic fan actuator.
Yeah the hydraulic fan isn't spinning very fast that's for sure ...I siphoned the Mercon out of the reservoir and it was really milky to say the least...still going with the rebuild though ...all the rubber hoses look like hell and why not put the S-Type T-stat housing on ...I'm thinking about experimenting with that aluminum degas reservoir ebay also ... ty his LSE will need some suspensionparts sooner than later ....O Boy here I go again rescuing an old LS from the grave ha ha ha ..by the way the DATC panel started working now both passenger and driver side Dual climate control digital temperatures work when pressing buttons up and down...my forscan isnt connecting up with the car anymore though ...works fine with the 06' but the LSE doesn't want to connect ...scratching my head on this ...PCM? It sucks because I want to run live data but I'm unable to connect with it...
 
Yeah the hydraulic fan isn't spinning very fast that's for sure ...I siphoned the Mercon out of the reservoir and it was really milky to say the least...still going with the rebuild though ...all the rubber hoses look like hell and why not put the S-Type T-stat housing on ...I'm thinking about experimenting with that aluminum degas reservoir ebay also ... ty his LSE will need some suspensionparts sooner than later ....O Boy here I go again rescuing an old LS from the grave ha ha ha ..by the way the DATC panel started working now both passenger and driver side Dual climate control digital temperatures work when pressing buttons up and down...my forscan isnt connecting up with the car anymore though ...works fine with the 06' but the LSE doesn't want to connect ...scratching my head on this ...PCM? It sucks because I want to run live data but I'm unable to connect with it...

Well that little actuator controls fan speed but of course it is controlled by something else.
Milky hydraulic fluid? Hmmmm no idea on that unless maybe water got in and the fluid is boiling too? I dunno on that one.
 
The PCM drives the fan actuator.
I can't remember... Does Forscan ask if it is CAN or not. Your 2nd gen is CAN, but your 1st gen is not.
 

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