Pathetic interior cabin heat

I have a 1999 Carrera 4 tiptronic. Bought it in December and the heat did not work, although it was happy to blow cold air. The tech guys at the dealership checked the temp of the hoses and they were at 40 Celsius and the temp out the vents was good when they had it, but after picking it up, it didn't work again. The figured teh radiator was clogged. I bought one and installed it myself (PITA) and got warm air out of it, but took a long time (15 min driving) to get it. This morning the drive to work it was getting warmish by the time I got to work. This is just not acceptable. Is there anything else I should be looking at to get heat in the car? Tech guy said they checked the blend doors and they all worked, but I have not visually checked that yet for myself.

Hmmm...since you are in Canada, I figure the ambient air temperature is pretty low. And 15 minutes of driving is not enough time. Even here in sunny Florida, on a 60 degree day it will take more than 20 minutes of run time to reach operating temperature, enough to blow warm air in the cabin. Maybe take the car for a longer drive and see if warms up. And by radiator, you mean the heater core? Very difficult to burp all the air out of the system after doing that. I assume you followed the specific directions for burping the coolant system. Also, in case you are inclined to start it up and let it idle until it gets warm, that is not recommended and is not a good idea..

Mine warms up quickly in the cold weather. What temp is your gauge showing? Maybe your thermostat is stuck open . 40 deg c pipe temp won't put any heat in the cabin .

Someone suggested the thermostat to me as well. Ambient temp today is around 0 Celsius, and the heat still sucks. Engine temp on the gauge is 60 - 70 Celsius but didn't get up there until I got to work, really. Same with yesterday after I switched out the radiator and drove around. I did get some nice warm heat after 30 min of drivng, but not hot. Temp gauge was around 80 and outside temp was around 0 as well. To get the thermostat I have to remove the waterpump, correct? ... I really don't feel like doing that ...

So thermostat is the next one to look at to get heat again? Is there a way to see if it is stuck?

i driven with temps a little below 0C and the car heats up fairly quickly and the heat is working fairly good in 5 mins and is hot as hell in 10.

OK, so something is messed up.

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definitely. It takes me about 5 mins to get the interstate and the air is warm. 5 more mins after i get on said interstate (doing 70-75ish) and the air it hot.

Thermostat is under it's own separate cover attached to the engine block. You do not need to remove the water pump. If it is stuck open, then too much coolant flows to warm up properly. If it is stuck closed, no coolant flow, but that should be apparent because the engine would get very hot quickly. There is no way to check it unless you remove it, and if you do that you might as well replace it. You will also need at least a gallon of Porsche antifreeze to mix and refill the coolant system. Due to the location of the thermostat housing and thermostat, you will lose almost all the coolant in the engine when you remove the housing hose (unless your coolant mix is fairly new I would recommend draining and replacing as opposed to using the coolant drain plug to drain the coolant and re-using it). Here is what you are looking for http://www.autoatlanta.com/porsche-parts/hardparts.php?dir=996-99-05&section=105-00

From my experience , if the thermostat is stuck open , you will likely see the Temp Gauge never go past 1/4 of the display. No matter how long you drive.

OK. Mine almost reaches 80 Celcius - probably 70 max after driving around 30 min.

Something is wrong. 70 degrees celsius is only 158 degress fahrenheit. Should be more like 82 celsius. I think your thermostat is stuck or someone put in a low temperature thermostat, and with the low ambient temperatures, the engine does not warm up completely to produce much heat. I have a 180 degree thermostat and on a cool day it will pump out heat enough to cook something.

Is there a way to confirm if it is stuck open?

Nope and yes....pull it out and put it in a pan filled with water and a thermometer on the stove, heat it up to 180 to see if it fully opens. But since you have it out, replace it and forget testing it. They can go bad. Recommend this and some reading https://lnengineering.com/products/o...e-install.html

Sigh ... As I don't know what else it can be, then I will have to replace it - unless someone knows of something else I can check?

Well, you said the tech guys checked the blend doors and they all seem to be working...but you could always check by putting the system on recirc and putting a plastic bag over the pollen filter to seal out the intake of outside fresh (cold) air and see if it pumps out some warm air. Did it ever puke out all the foam bits that cover the blend doors?

I do get warm air after a time, but not hot. The warmest I do get is on re-circulation. I will try this when I get home though and see if it gets any warmer, though. Also, when I checked the coolant hoses leading to the radiator heater behind the battery after running for 30 min, they were warm to the touch, not hot.

They should be HOT HOT...like I can't touch this hot. Still pointing to a bad thermostat, or air in the coolant system.

I am driving with the valve open, so I am hoping that will get the air out.

I have to agree with the thermostat, sounds like what happened to my Acura YEARS ago.

I just did an engine coolant drain and refill because I broke the plastic fitting on the coolant tank to water pump hose and had to replace it while doing new motor mounts. PITA! When i refilled the coolant tank and ran the engine, coolant tank cap off the level dropped a lot. Then refilled the coolant tank and left the bleeder valve manually open for at least 5-6 full heat and cool cycles, checking, opening the coolant tank cap and refilling each morning. It takes a lot to get the system air-free again.

Question is,do I want to do this myself with my limited tools and the hassle of the coolant? The heater core was easy, but I was surprised at how much I had to disassemble to change it out.

I will keep trying to bleed this out first and see if things impove. Then I will do the thermostat. Listen, guys, I appreciate this help, so thank-you. Just wish I could concentrate on doing the more fun stuff, like revamping the interior and such.

It doesn't sound like you're that into working on it, but maybe you could have a shop vacuum fill it? If you like working on it, an Airlift (or copy) and a compressor will allow you to vacuum fill the coolant, and eliminate any trapped air.

The Porsche tech guy recommended that too. I think it may be a good investment anyway for me.

Again today going home. Long time to just get warm. Temp gauge never got to 80 Celsius after a 30 min drive.

I had very similar issue and it was the blend door foam. Applied new foam and hot heat returned.

Just had my thermostat replaced as the engine never reached operating temp when it was around 3 C. outside. Made a big difference in the operating temp. . Don't recall how well the heater was working, sorry. Just remimber having a jacket on when driving to the shop for some other work. Coolant was being replaced anyway so they replace the t-stat at the same time.

The blend door was always my thought too, but the hoses for the heater core are just not hot. Warm, but not hot, so I think that everyone saying it is the thermostat is probably right. Unless I still haven't bled out the air in the system.

The heater core is fairly high up and it is really hard to get the air out of it. If your temp gauge is normal but no heat there could be an air lock in your heater core. Best way to get the air out is using a vacuum fill but some have had success by putting the rear only up on ramps to get the heater core lower down in the system and burp the air out. To bad you aren't in Ontario, you could pop by and I could vacuum and refill in like 15 min .😀. I have the tool from Amazon and it works really well. UView 550000 Airlift Cooling System Leak Checker and Airlock Purge Tool Kit Amazon Amazon

Lol. Yup, I'm in Edmonton I will try that. Monday I will pick up a air vacuum from somewhere. Worth a shot before I do the thermostat.

I edited my post above, to show the one I got from Amazon. It works really well.

Pricey ...

Please just replace the thermostat, then you can use your new vacuum tool to refill it.

Ok. I replaced the heater core, which seemed a waste of time, but it at least was husband and wife time on her car. Burped the co plant system. Then we did the thermostat, which was sticking it seems. STILL no actual heat. Warm, but no heat. the hoses to the heater core fee, nice and warm, but NOT hot. I am at a loss as to what to do next. Anyone have an idea? Frustrated ...

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Jim, i'm in the same boat as you. The air gets "warm", but not hot. I have a new thermostat and it did nothing to alleviate the symptoms. I'm curious as to how I would diagnose and repair this issue if it was the blend doors/foam. Is that something a regular guy like me to tackle, or does it involve removing the dash and getting into the guts of the car? If anyone has any ideas or tips, please post! Thanks!

I'm changing out my dash to a leather one with glovebox, so that will be the perfect opportunity to check all the blend doors and ducting. If you are not afraid to disassemble the interior, this is not a big deal, but pulling out the dash is a 2 person job. There is nothing else to check for me. Either this is how the heating in these cars is, or a blockage in the line? Lines were checked, though. Would love to have another 996 to compare with.

Mine has crappy heat too, even in Tennessee. Turn your blower on high -- do you get showered with foam? If yes, blend door foam is deteriorating. If no, blend door foam deteriorated and is now gone. Here is a thread on the issue, with links to tackle the issues with or without dash removal: https://rennlist.com/forums/996-foru...oam-at-me.html

Yes, my foam is deteriorating. I figure I will clean it all up when I pull out the dash. So heat really is just crappy in our cars?

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No, they have excellent heat and air. The metal blend doors are full of speed holes. Once the foam that coats them is gone, these holes allow the hot/cold air to intermix. The fact that the heat or AC works at all is testament to how potent they should be.

Then that is my last step. Oh well. A new heater core and thermostat. Guess I can try and sell my heater core. Thermostat was working but crusted up, so probably would have needed one anyway. I will be ripping out the dash later this month or early May. Thank-you Tyler! This gives me hope. Its cold up here in Alberta ...

Hey Jim, I'm pretty sure you had a look at the my car in the Fall with your wife and son. Anyway I'm in Edmonton and drive my 99 year round, Cabin heat is very effective regardless of outside temperature, so the problem you're experiencing is not due to poorly designed heating or AC

Maybe the cabin temperature sensor is bad? It lives behind the round grill above the passengers right knee. I think there is a fan and other hardware in there. That still doesn’t explain the cooler engine temps. http://www.design911.co.uk/fu/prod13...che-986---996/

Well at least the sensor may be one more thing to check at least. I am definitely checking the foam next though. Just need a weekend free to do it. Azraely, yes that may well have been me! Ok. Good to know that it should put out real heat. So the blend doors foam are making more sense to me as i read the posts. however, I will say that the hoses leading into and out of the heater core are very warm, but not hot. I can hold them with my hand.

I'm going to chime in on this - years ago on my car the foam started coming out the vents. I cleaned the little bits out of the vents for months and finally it stopped. I read up on the issue and fixes and decided there was no way I was going to pull the whole dash apart to get to the HVAC unit. And you know what? I have found that it makes no difference. I get very hot air when the heater is on, and very cold air when the AC is on. Before you tear into your car, there has to be some reason that the car is running "cold" (your posts about the engine temperature) and the heater hoses are not getting much more than warm. I have no suggestions on what to look for next, but there has to be a correlation between engine not getting very warm and pathetic heat from the heating system.

I'm open to ideas. After the thermostat change the car did get to 80 Celsius , but took a while.

When, if ever, has the water pump been changed? The plastic composite impeller does wear and maybe it is not pumping enough coolant. Just a thought....although I would think that that would make the engine run hotter, not cooler. Hmmm...maybe enough coolant circulation for the engine but not enough to reach the heater core. Just guessing at stuff right now. Did you block off the outside air intake like I suggested? Just place a plastic bag over the pollen filter. One other question, are your radiator fans running? Do they work? Is the ambient outside air temperature sensor correctly fitted in the front bumper? Another question, what type of thermostat did you install? The only thing that controls engine temperature is the thermostat. If the engine is not getting hot enough, something is wrong with the thermostat (or the radiator fans are running all the time). Do all the controls on the HVAC work? Are you running the HVAC on auto, or leaving that off and going up to the highest temperature on the display?

I agree with DBJoe, you need to figure out if the HVAC is not extracting the heat from the heater core, or if the heat is never getting to the heater core. Scientifically speaking, heat (energy) can not be created or destroyed, only moved or changed in form.Also there is no such thing as "cold", it is the "absence of heat" Since your in Canada and the ambient air has most of it's heat removed, I would perform tests in a closed garage ( with exhaust routed outside) to minimize the effect of ambient air and especially wind, and in having the car stationary will maximize heat concentration. Since the heat (engergy ) of the gasoline is released or moved during combustion, some is used for energy to turn the crankshaft, and some is transferred to the oil/coolant. Use a Laser thermometer to check temperature of the coolant hoses and heater core hoses, the temperature of the engine outlet coolant and the inlet of the heater core should be very close to the same. You must find where the heat is going, or not going. You can use this HVAC hack to get some temps from varing sensors to help in diagnosis. To access diagnostics: Hold down the Recirculating & Air up buttons for 5 seconds. The + - buttons go up and down through the list of "c" codes. The center vent button switches the left display between the "c" code and its actual value. Press the Auto button to exit. Here is a list of what can be seen: 0c - ERL 1c - Oil Temp? 2c - Inside temp. Sensor mounted in the aspirator assembly at the side of the dash. 3c - Outside temp. Sensor located inside the air inlet of the A/C unit. 4c - Outside temp. Sensor located in front grill of the radiator. The data is fed to the Climatronic from the instrument cluster. When not moving, the instrument cluster OBC temp display retains it's last setting until moving. This is to prevent heat emanating from the radiator affecting the temperature sensor. The A/C unit uses the lower of the two outside air temp values in determining fresh-air temp. 5c - Outside temp. (matches with OBC outside temp display) 6c - Coolant temp. 7c - Footwell discharge temp. 8c - Sun sensor (dash top) 9c - Sun sensor. 10c - Passenger compartment fan speed. 11c - Passenger compartment fan voltage. 12c - Temperature mix Flap command 1=COLD, 100=HOT 13c - Temperature mix Flap position 14c - Central Flap command 15c - Central Flap position 16c - Footwell/Defrost Flap command 17c - Footwell/Defrost Flap position 18c - Recirculation Valve command 1=OFF, 100=RECIRC 19c - Recirculation Valve position (feedback) 20c - Vehicle speed in kph, updating only once per second. (real speed, not speed+safety margin as in the speedometer) 21c - Engine RPM in hundreds. This too only updates once per second. 22c - ? 23c - ? 24c - Sun sensor, exterior lights switch & panel lights control (term. 58 & 58d voltage) - used for A/C panel display illum. 25c - ? 26c - ? 27c - ? 28c - Fan speed? 29c - ? 30c - Engine run time in seconds (255 max.)(=0xff) 31c - Timing counter 32c - Displays test 33c - Software version? Mine states 3.4 34c - ? 35c - Outside temp. from inlet sensor (filtered?) 36c - temp? .

I'll take time later to read your post in more detail, but to answer a few things: HVAC functions were all tested. tested heat on manual high and recirculate. Recirculae is the warmest. Thermostat installed by Porsche. temp got to 80 gayer driving a while hoses to heater core are very warm but not hot. I can hold them water pump impeller blades in good shape.

Huh. I would borrow or buy an infrared thermometer and measure the temperature at the thermostat housing and then the heater hoses. They should be about the same temp.

My father in law has one. I will check Friday

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I dont have any ideas, but there is something for sure wrong. The heat on these cars, even in sub freezing conditions, should be enough to run you out of the car in 10-15 minutes.

My car has similar symptoms. On a cold morning, I have the temp set to maybe 74 or 76, figuring the controller will know it's cold in the cabin and then crank up the heat, but then after 10 minutes it still doesn't blow nice hot air, only warm air. But if the temp is set to max, 85 or something, then suddenly in a few seconds very hot air starts coming out of the vents. Has anyone noticed something similar? I don't think it is related to the thermostat, but maybe the temp sensor is degrading?

I think your problem is that the foam on the Heater/AC diverter (flap) has deteriorated which causes a loss of heat. There seem to be lots of threads about repairing the foam on the flapper. Evidently this problem affects all 996s!

Im sold on the idea of the foam too. Just the hoses to the heater core only being quite warm rather than hot makes me wonder.

You mentioned Porsche did the thermostat. Did they vacuum purge and fill the system? If not perhaps it's trapped air? I've got a Schwaben vacuum system here from last years rad/fan replacement that I'll send to you if need be. I don't expect shipping from Revelstoke to be too much. Also don't expect it'll be difficult for you seeing some of the work you've done so far and with DBJoe and Porschetech3 on board surely you'll get to bottom of this.

They assured me they they gat trapped air out. I made sure to ask after you guys pointed it out after I did the heater core.. And I am very appreciative of the help. The Porsche tech says he goes on here too for troubleshooting, so he may well have read this thread.

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I agree with your statement. My car has finally stopped burping foam so I assume it is finally gone. On a Texas cold day I get heat pretty quickly but on a Texas hot day the A/C keeps up to about 90 degrees outside with the top down. It seems to work pretty darn good especially because the top is down most of the time. With that said my temperature typically gets to the zero in 180 within a few miles and stays there.