Wtf coolant heat problem

[Petatew]

SO first of all sorry for my english is not my first languages

I have a 2011 b8 s4 with 130k on it

WINTER:2015-2016 no heat at all in the car except at wot

SPRING-SUMMER 2016 I thought the problem was the waterpump with a stripped shaft on the impaller so at wot it made enough ''flow'' to push coolant in the heater core and have heat in the car.
I remove it,it was in perfect shape already the metal one not the plastic nonetheless i change it for a new one and in the meanwhile I change the Thermostat

AUTUMN-WINTER 2016 now i have heat at wot ,on the highway when I'm cruising at 70-75 and up and on random moment like at 30 mph no where I have heat for 15-20seconds.

over all that even before/after those repair, I'm having coolant ''leak'' i said ''leak'' (no leak anywhere nothing wet no smell nothing )because only when its arround -2/2 degree celcius I will lost coolant 50% of the tank when its really cold i dont loose it and i'm never loosing it in summer never had any temperature problem from the car never overheated

thanks you for your help

[theweebabyseamus]

Thermostat issue?

[Petatew]

I changed it same time than the waterpump but never had any issue with the old one i just suspected that maybe he dont fully work so i changed it

[blackjak]

Heater core? Are you sure you have enough coolant in your tank? That after he therm has been allowed to open up and allow the resign or tank to empty some that it's not completely empty? I know this may sound stupid, but if it's intermittent than either something is going out or the coolant is only getting to the heater core under certain conditions. I could be wrong...

[TexasDfwS4]

White smoke?

[Petatew]

No white smoke. At all my oil is good too so no mix of oil/coolant by the headgasket.


Yea its look like the coolant reach the heatercore only on certain conditions. But that exactly why i found it strange... But yeah my coolant level is ok

[FWP!]

Air in the system?

[mdmay]

I would check your hoses to see if you have a hole any of them or a rusted union somewhere allowing water to escape

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[Petatew]

I'm sure no air in the system since I've done 20 000 miles since I've done the waterpump/t-stat if it would have had air in the system by they time the air would have come out


I will check the hose again today but since i've no smell of coolant nor mark in my driveway i don't suspect it but i'll stil checking it soon

[shadycrew31]

Its possible the valve for the heatercore is stuck and not opening fully. I believe there is both an electronic water valve and a vent that needs to open not 100% on that though.

If you have a thermocouple or something you can measure surface temps with you can see the in and out temp of the coolant going to the heater core. Based on that data you can determine next steps

1. If the temp coming out of the heatercore is the same as whats going in air is not moving across it, this could be the hvac issue.

2. The water temp going in is significantly lower than the rest of the system. Coolant circulation pump (electronic) is failing or valve (electronic/pressure) is only operating to a certain point.

3. Water going in is up to spec, coming out is very low. Blockage in the heatercore or large air bubble is present.

[SwankP3RF3ct10n]

Run a scan with VAGCOM and see if you see any codes for the temp sensors for the heater core or any other module. There is a module (I forget what it's called now) that I think is in central electronics that if it trips, weird things happen with the A/C and Heat only working when the car is not moving. I tripped it once during an emergency stop... no idea how or why it tripped, but it did. Clear any codes you might have and check the conditions of the heater again. Also, like shady said, check the sensors and electronic valves controlling the flow of coolant through the heater core, could be that.

[Dr GP]

Have you checked out this thread? http://www.audizine.com/forum/showthread.php/743337-Second-thermostat-sticking-open-New-working-thermostat-part-fix-Any-info

[S4'ed]

Air in the coolant system. You need to bleed the air out. It will not bleed out by itself, no matter how much you drive it.

[shadycrew31]

Air in the coolant system. You need to bleed the air out. It will not bleed out by itself, no matter how much you drive it.

You can burp it by letting the car warm up on jackstands or ramps with the cap off.

[flopinator2000]

I have a 2010 with 122k on it....same issue pretty much. I only get heat at 3k rpm's and up. I can sit and let the car warm up, no heat until I drive. I'm saying its my heater core. I've tried bleeding the coolant the way it says in the manual 5 times now and nothing. You have to slide off the one heater core hose until coolant comes out the little hole and hold it the RPM's at 3k.....its pretty much impossible to do this with out the hose popping off...even holding it.