boiling like sound from heater core

[aga]

sup guys. i had a faulty vent nipple in the radiator neck, so it wasnt operating properly (the coolant would not return in the system when cold) so i always had a bit of air in the system, which resulted in a boiling like sound from the heater core after i shut down the car.

now i fixed that, also replaced eeeeeeeeevery hose in the system and fixed every leak, and as i shut down now, here is the sound again. i know there's still a possibility of existing air in the system as my car needs a few warm cycles and filling up in between to get rid of all the air, but i just wanna ask, does anyone else have that sound?

[bmxer882x]

don't have the sound but try just bleeding your coolant system. either put it on jacks or just park uphill and let it idle with the radiator cap off and heat on until its warm and has ran for 10 minutes or so. Should force all the air to the top and add coolant if needed.

[aga]

thats what i do, i park uphill, and each morning before going to work i top off if needed. usually it takes 2-3 times before its fully bled.

[fliprayzin240sx]

Swirl pot is your friend...

[aga]

Ι have one, haven't installed it yet...

[aga]

could it be, that the sound is dripping, instead of boiling? i hope i dont have to take the dash out again... but i prefer knowing the cause of a problem...

[fliprayzin240sx]

If its dripping, you'd know since things will be damp under the heater core.

[aga]

doesnt the s13 have a drain for the moisture that drips from the air con? my last car did, and when the heater core leaked, it dripped out from that, to the road.

on the other hand if it was leaking, i would smell coolant from the vents...

[fliprayzin240sx]

doesnt the s13 have a drain for the moisture that drips from the air con? my last car did, and when the heater core leaked, it dripped out from that, to the road.

on the other hand if it was leaking, i would smell coolant from the vents...

I didnt think that would be possible considering the evap and the heater core are 2 seperate units.

[aga]

well the good thing is that last two times i drove it, no boiling sound after shutting off, and the coolant level is top, and crystal clear. perhaps it blew out whatever air was left and now all is good. we'll see....

[sleepyS14se]

on my ka24de i had this same issue.

My solution was to remove the thermostat and fill the engine with a good 50/50 mix through the lower hose (no thermostat in).

My engine ended up having some massive air pocket and the routing of the rad hoses on it just do no justice when trying to bleed it.

[Mikester]

Funny, I have NEVER had to bleed a coolant system... Several warm/cool cycles and it usually works itself out.

aga- if you are not losing coolant, the heater works, temps are normal etc, then you sir are good to go.

[aga]

still does it... :( i have a tiny leak, 99,9% from the overflow nipple on the radiator neck...i dunno what im gonna do. if i find a solution, ill post it here

[codyace]

Epoxy/JB weld the overflow neck area, or have it welded if aluminum.

[Def]

I'm guessing you have an SR20DET - this is entirely normal. Especially on the engines that have a turbo coolant return to the long ass line behind the head that I think is the return for the heater core. It boils coolant, more gets drawn in, etc. until the turbo CHRA is cooled down.

This is how it's supposed to work. It's much louder when you have the turbo coolant return to the radiator supply hose since you can hear it right there when you pop the hood open.

[aga]

I'm guessing you have an SR20DET - this is entirely normal. Especially on the engines that have a turbo coolant return to the long ass line behind the head that I think is the return for the heater core. It boils coolant, more gets drawn in, etc. until the turbo CHRA is cooled down.

This is how it's supposed to work. It's much louder when you have the turbo coolant return to the radiator supply hose since you can hear it right there when you pop the hood open.

that sounds logical.you gave me some peace of mind.

someone should make transparent coolant hoses , to inspect stuff like this. but that would only make me more paranoid :eek3d:

[Mikester]

aga, I've never once heard of any type of boiling sound being normal. The whole point of keeping the cooling system under pressure is so that it does NOT boil. I've had SR's with the line in the rear and my current setup with the return going to the water neck. No sound noted.

Your system leaks... That's prolly why you're hearing it boil- Because there is somewhere to let the pressure out; resulting in boiling coolant.

[aga]

the only thing that remains is a leak in the overflow nipple. which it isnt a leak in itself, but it does result in loss of coolant. when the pressure builds up, it spits the extra coolant out, but due to the leak it cannot suck it back in properly, or sucks air instead, which ends up in the system. i gotta fix this because...

http://fc01.deviantart.net/fs71/f/2012/151/7/3/summer_is_coming__by_naomi89-d51rrw1.jpg

[Def]

It's ENTIRELY normal. You're a deaf MFer if you have a watercooled turbo and you've never heard the coolant boiling upon shutting the car down. That's how it circulates water in the CHRA.

Garrett white paper | Turbo white paper (http://www.turbobygarrett.com/turbobygarrett/Garrett_White_Papers)

White paper on turbo cooling will explain it all. It's called thermo syphoning if you want to read more up on how this works.


The only janky thing about S chassis cooling systems is using the top of the radiator as the expansion air space. It doesn't work for crap if you drive your car hard, and will pop the radiator cap in short order. Give yourself more air volume to expand into with a surge tank and it fixes all that. Surge tanks don't work by removing bubbles or whatever stupid crap I've heard that they do on this forum.

[aga]

what garrett says is that warmed coolant rises, and cooler takes it's place. it doesnt have to boil to do that... boiling is a result of the system not being pressurised, because of the existence of air. that's what i believe anyway.

[Def]

what garrett says is that warmed coolant rises, and cooler takes it's place. it doesnt have to boil to do that... boiling is a result of the system not being pressurised, because of the existence of air. that's what i believe anyway.

Being pressurized, the coolant has a boiling point that increases by roughly 40-50 deg F depending on your radiator cap pressure and ambient pressure. It will still boil in the CHRA when you shut down the car. The boiling just quickly circulates coolant... the thermosyphon effect isn't fast enough right after shut down, but will work for a while after it stops boiling.

Trust me, I run a 20 psi cap on my car and it would boil it's ass off after driving hard every single time.


...and I don't mean to be a dick, but I'm an engineer and your "gut feeling" of the physics of the situation is wrong.

[Mikester]

Being pressurized, the coolant has a boiling point that increases by roughly 40-50 deg F depending on your radiator cap pressure and ambient pressure. It will still boil in the CHRA when you shut down the car. The boiling just quickly circulates coolant... the thermosyphon effect isn't fast enough right after shut down, but will work for a while after it stops boiling.

Trust me, I run a 20 psi cap on my car and it would boil it's ass off after driving hard every single time.


...and I don't mean to be a dick, but I'm an engineer and your "gut feeling" of the physics of the situation is wrong.

:hahano:

Hmm, bold statement.

Dude, your cooling system and/or coolant line placement must be inadequate to ensure a proper thermal siphon- meaning that your CHRA is becoming heat-soaked; resulting in boiling. Thermal siphoning is achieved by convection; NOT boiling (both of which however are cooling processes BTW; but only the former should be happening in a turbocharger via thermal siphoning). If there is boiling happeneing in the chamber, then that means there are air bubbles being produced in the system, that would migrate to the top of- well-away from the water inlet/outlet (that should be positioned around 20* of horizontal according to the whitepaper you supplied)... meaning the coolant chamber size and/or coolant quantity need to be increased; or the water pump or radiator need to be upgraded.

Doesn't matter how many psi the radiator cap will hold- we're only talking about an extremely small portion of the cooling system that would have its work cut out for it trying to heat the rest of the system to sufficient temperature to force coolant into the overflow on its own- Let alone cause it to boil.

Coolant should never boil... nor is it normal. Going back to the whitepaper, the word 'boil' is nowehre to be found in it (imagine that). Don't get me wrong- I don't doubt you are great at whatever it is you do career-wise... and I also don't mean to be a dick when I say that my "gut feeling" here is that your primary area of engineering expertise is probably not thermodynamics.

For the record, I use thermal siphoning to cool my house down all the time in the spring & fall. So far, nobody has boiled to death on my watch.

:D

[Kingtal0n]

Don't get me wrong- I don't doubt you are great at whatever it is you do career-wise... and I also don't mean to be a dick when I say that my "gut feeling" here is that your primary area of engineering expertise is probably not thermodynamics.


:D

Def is a nice guy, and I trust him when it comes most subjects, but... thermodynamics and Def do not mix. We got into it once he again brought up his job and used it as "I am right because of my job" sort of like he did here. And when I asked for explanation he offered none, his attitude was "you figure it out I dont need to explain it to the little people just trust me im an engineer!". Not very nice! But I still trust him in business, and consider him a good person and friend :D

[Mikester]

Def is a nice guy, and I trust him when it comes most subjects, but... thermodynamics and Def do not mix. We got into it once he again brought up his job and used it as "I am right because of my job" sort of like he did here. And when I asked for explanation he offered none, his attitude was "you figure it out I dont need to explain it to the little people just trust me im an engineer!". Not very nice! But I still trust him in business, and consider him a good person and friend :D

Oh no doubts he is a cool dude & smart guy. Although I sincerely do not agree with him on this particular point- that part of my post you quoted was intended in good fun ;)

[aga]

last friday i hit a pothole going reverse into a parking and thought i hit my oil pan. i get under the car, i see fluids running down. turned out it wasnt oil, the car had sprung a coolant leak. it was pure luck i saw it. anyway to cut the story short there was a coolant hose under the intake manifold that i hadnt seen, and i replaced that too (all the other hoses had already been replaced with samco) ...fixed the overflow nipple too, so now the system is perfect i believe.

it still boils when cooling down. you can't hear it so loud, which is because the system performs better i think, but it still does it. and i put my ear to the turbo return, its obvious that's where it originates. but because the heater core is in the cabin and it creates a kinda "speaker" effect, thats why it's more obvious there.

i wonder if it happens to stock s13's too

[Mikester]

No. Just to be sure, I ran the living shit out of my car yesterday- no boiling sounds. Wish I was near you... Wonder if there is air in the system still.

[aga]

I am actually in the shop right now. Goddamn car sprung another leak lol. I'll keep you posted

[aga]

the system is fine now, i have been monitoring coolant levels for a week, its great. however the boiling thing continues. sure its from the turbo, i can hear it if i get close enough...

SO, here's my question. in genuine s13's with SR20DET, where does the turbo coolant return go? obviously it doesnt meet the heater return as in my car, that would make all stock cars make that sound... so?

[Mikester]

In stock form, the turbine coolant return goes behind the head and back into the under-intake coolant piping. Personally, I'd recommend either an S14 water neck or DIF/Stance water neck adapter and plumb it there- Eliminates the coolant line behind the engine, and much easier to work with.

[aga]

my engine is s14, and its got a plugged hole on the coolant neck. should i put the return there? i'll get a picture tomorrow.

[aga]

if im not mistaken, the upper rad. hose spits coolant into the radiator and the lower sucks it through the pump, into the block, right? so the feed of the turbo is on the block, and the return would be on the neck.

am i saying it right?

[Mikester]

Don't bother- yes you should. IIRC, the OEM S14 config is coolant return at the water neck.

[bent87]

Hi
Did you fix it? Got the same problem. And it is killing me!... :(

[aga]

yes i fixed it. the turbine coolant outlet was going behind the engine and into the heater core, then back to the engine. Garrett turbos are made in a way that when you turn the engine off, the water is still circulating by using it's own temperature, and thus cools the turbo down quicker. i plumbed the turbo coolant outlet elsewhere (its been a long time,but i think to the neck that goes to the radiator) and left the heater core on it's own. i hear a slight bubbling from the engine when i turn off, but its nothing compared to the sound i used to hear in the cabin. the bubbling is the coolant in the turbo boiling, and making its way to the radiator.