Would a slight leaking J-Plug cause a "heat only works under acceleration" condition?

[n7plus1]

Considering is effing freezing outside, i didnt do a full once over, but i did smell coolant after i popped my hood. I noticed yesterday that my heat only works under acceleration and typically I know this is only caused by having air trapped in the system. I did a quick burp of the coolant yesterday morning via the coolant tank and got just a small, tiny grumble. After looking today I noticed there was a small wet spot near the thermostat housing. I replaced the TS ~ 2 years ago BUT I never did the damn J-Plug. There were traces of pink crystallization where the plug meets the block. Would that little thing cause the above said symptom? I cant imagine theres a significant amount of air coming in through that screwed up o-ring? or would that very well solve my issues?

While we're at it, would this cause a random (not every day) engine hiccup while idle? If im watching my boost gauge, sitting at a red light, engine idle reads -20/-21Hg...and then randomly the engine will rev itself to like -15Hg or so and then go back to normal. I wasnt sure if the coolant system taking in air could throw off the vacuum system? I ripped out most of my vacuum system, so if not, ill comb through that and see what i can find.

[Mike@PureMS]

Probably not likely. Your intermittent heat is likely due to a clogged heater core, or a failing water pump.

Your engine hiccup is something else entirely.

[n7plus1]

i cant imagine the heater core is clogged. i flushed it out years ago and my coolant has stayed cleaned since. water pump was replaced about 20k ago.

[ZipMeUpJ]

Im having this issue after recently swapping in a new behr tstat and a new jplug. I havent checked for a wetspot near the jplug after install. It actually would not go into the hole when I had the actual fastener end up against the block. But turning it towards me it slid in easily. then i just twitsted it back up to the block and put on the bolt. Air must be getting in the system somewhere but my coolant level isnt dropping. theres condensation on the inside roof of the coolant tank and trying to burp the system doesnt seem to be doing anything. But when i got on the highway heat was fine. im stumped at the moment.

[n7plus1]

I put in a new MAHLE T-Stat back in March of '12...and i just noticed the heater core hose from teh core to the rear coolant flange is leaking around its seal, which was replaced 2 weeks after. Im blaming ECS on that one, just contacted ECS about that one a little bit ago. I hate this car.

[n7plus1]

checked the heater core hose in the second firewall location and the bottom was warm and upper one was not. Im assuming the heater core is clogged...time to get some CLR.

im a bit confused how it could be clogged as my coolant is crystal clear?? an insight? fletch, where you at man??

[old guy]

Hi Nate. Hate to tell you this but right now I'm feeling your pain. Several years ago I had to deal with a no heat situation. Did some bleeding, replaced the thermostat as a preventive measure and while I was at it replaced the J plug. Flushed the heater core and got the heat back. It lasted for a few years. At the beginning of this winter the heat had begun to degrade so last November I flushed the heater core again. The heat came back strong.

Now two months later I'm losing heat again. A few weeks ago I did another quick heater core flush by just clamping and disconnecting the heater core hoses and ran a garden hose the core. I reversed the flow several times, used compressed air to evacuate the core and refilled with fresh coolant. It helped but is still not back to what I know it is capable of putting out. Like you, my coolant is clear. I have flushed and replaced the coolant at least four times over the life of the car.

I think I am going to bite the bullet and go ahead and replace heater core as soon as I have a chance. Don't feel like dealing with it again.

[ddillenger]

Get some fleetguard restore and restore plus. It will decimate anything in your cooling system that should not be there. The first (restore) cuts the oil, the second (plus) gets rid of buildup.

[AutoUnionLov3r]

Get some fleetguard restore and restore plus. It will decimate anything in your cooling system that should not be there. The first (restore) cuts the oil, the second (plus) gets rid of buildup.

Sounds like a pretty solid solution! I've been experiencing the "heat only above 4k" and a quick burping of the system was all I needed. I've never flushed my heater core in my 3 years of owning my car so it'll be a nice spring cleaning project, along with MUCH other much needed maintenance.


Sent from my iPhone using Tapatalk 2

[Rausch]

I have the same thing going on with my heat. I'll be replacing the heater core and adding an auxiliary electric water pump in line with the heater hose.

[MikTip]

A test...

Do you have heat with the temp set to high?

Mine only produces heat with the electronic controller temp to high.

So makes me believe it the electronics controlling/moving the air flaps inside up under the dash...as I have already replaced my controller...

I've tried to reset everything with VCDS....still same issue...only heat when set to high.

[n7plus1]

i have my CC set to 69 and AUTO....heat still comes out if I keep the RPM's up...and its definitely warm and then starts blowing cool air as soon as i lift off the gas, etc.

Fletch, im not sure how much longer im going to have this car. Itd be gone by now if we didnt have the baby and if my wife was working full time....would you recommend flushing to core to see how long it lasts vs. just replacing the core?

the new WRX is calling me from the showroom...

[ZipMeUpJ]

When did you change your coolant sensors last?


I remedied this problem over this weekend by replacing my lower coolant sensor. Before replacng my thermostat I got an error for low reading something or other for the lower sensor. I cleared it and it didnt come back, but my heat was tepid like you are having. My heat would be so lukewarm and sometimes chilled even on high. It would take maybe 20 or so minutes (even with temp gauge at center) and driving at speed to get some heat then it would be fine after that. The gauge would even fluctuate up past center on occasion and once to trigger the coolant light, it wasnt dependant on engine load or anything, it was almost at random. So I parked it and troubleshooted. Unplugging the (g83?) sensor didnt turn on my radiator fans either. After plugging it back in I got the code fore low reading on the G83 again. Replaced it. Heat is too hot now. Im guessing my faulty lower coolant sensor was working on and off and hindering the ecu from turning on the radiator fans when it was supposed to or really needed it. Its been a couple days now and no problems yet. No leaks or nada.

[AlS6]

Probably not likely. Your intermittent heat is likely due to a clogged heater core, or a failing water pump.

Your engine hiccup is something else entirely.

Failing water pump? like the impeller blades are are all gone? or it stopped spinning? I don't quite picture this.

[Pothole]

Must be these B6's showing their age .
I have been chasing the no heat / heat only over 4k for the last few weeks.

Back flushed it with a garden hose like above and it helped marginally.

I really dont want to replace the core, that seems like a royal pain in the ass, but Im getting tired of driving to work in 2nd gear just to get some heat out.

[old guy]

Fletch, im not sure how much longer im going to have this car. Itd be gone by now if we didnt have the baby and if my wife was working full time....would you recommend flushing to core to see how long it lasts vs. just replacing the core?

the new WRX is calling me from the showroom...

A quick flush will be a lot easier than replacing the core and it may get you a little bit more heat. It did for me a few weeks ago. Nothing fancy, just clamp off both of the heater hoses at the firewall. I removed the battery just to give me a bit more room to work. After clamping the two heater hoses I disconnected them from the pipe nipples and connected two sections of clear hose to the nipples. Next I connected a garden hose with a twist head to the return side nipple and blasted water through the core. Then I disconnected the hose and reconnected to the supply side and did the same thing. I reversed back and forth several times and pulsed the water by rapidly turning the twist head on and off.

After flushing I used compressed air to blast out the water, reattached the lower heater supply hose and released the clamp. I used a funnel and a shorter section of hose to refill the heater core from the upper return hose. I then removed the short section of hose and reattached the return hose. Started the motor up and let it idle long enough to develop a little heat and pulled the upper hose back far enough to burp any air. Put the clamp back in place and was done. The whole operation took about 45 minutes and made a noticeable difference in the heat. It didn't get it back to where it should be but it is now tolerable.

It's certainly not the same as doing a chemical flush but it's relatively painless and can be performed in under an hour and should boost your heat a little. Unfortunately I don't think we are going to see any above freezing temperatures in our area until this weekend.

[oaybar007]

I'm in the same boat. Low heat in general. A little hotter at speed. I've had the heater core on my list of parts to replace, but that list is growing too fast these days.

Definitely sounds like your heater core needs to come out. As OldGuy said, flushing helps for a little while but ultimately the core will get clogged again. Thankfully, replacing the core itself is not too bad from what I have researched.

Check out this write up on replacing: Heater Core DIY

[24Peter]

I'm in the same boat. Low heat in general. A little hotter at speed. I've had the heater core on my list of parts to replace, but that list is growing too fast these days.

Definitely sounds like your heater core needs to come out. As OldGuy said, flushing helps for a little while but ultimately the core will get clogged again. Thankfully, replacing the core itself is not too bad from what I have researched.

Check out this write up on replacing: Heater Core DIY

New here. Registered to address the OP's issue: Marginal heat at least until the car [2004 A4 1.8T] is driven at highway speeds for several minutes. I'm not qualified to work on my own car and would need to have the car serviced, whether it's flushing the coolant system and heater core if that's separate. I think that's around $200 at my local Audi dealer. My question is, what if I need to have the heater core replaced? I'll call them for a quote, but any suggestions on the cost and any other cost-effective way to address the issue or make the repair? Also, could this be a thermostat repair? What do you guys think that would cost?

And since money is tight right now, what happens if I wait (besides freezing my a$$ off)?

[n7plus1]

A quick flush will be a lot easier than replacing the core and it may get you a little bit more heat. It did for me a few weeks ago. Nothing fancy, just clamp off both of the heater hoses at the firewall. I removed the battery just to give me a bit more room to work. After clamping the two heater hoses I disconnected them from the pipe nipples and connected two sections of clear hose to the nipples. Next I connected a garden hose with a twist head to the return side nipple and blasted water through the core. Then I disconnected the hose and reconnected to the supply side and did the same thing. I reversed back and forth several times and pulsed the water by rapidly turning the twist head on and off.

After flushing I used compressed air to blast out the water, reattached the lower heater supply hose and released the clamp. I used a funnel and a shorter section of hose to refill the heater core from the upper return hose. I then removed the short section of hose and reattached the return hose. Started the motor up and let it idle long enough to develop a little heat and pulled the upper hose back far enough to burp any air. Put the clamp back in place and was done. The whole operation took about 45 minutes and made a noticeable difference in the heat. It didn't get it back to where it should be but it is now tolerable.

It's certainly not the same as doing a chemical flush but it's relatively painless and can be performed in under an hour and should boost your heat a little. Unfortunately I don't think we are going to see any above freezing temperatures in our area until this weekend.

thank you sir, i always appreciate your input. Fortunately enough, I wont have time anyway until the weekend now with the little one (my wife works part time evenings) so he takes my nights and its been cold as hell and gets dark so fast now anyways. I may just get a bottle of CLR too. Ill probably do the above and after using compressed air to blow it out, dump in the CLR and leave sit for a bit and then come back and flush it all out again.

I'm in the same boat. Low heat in general. A little hotter at speed. I've had the heater core on my list of parts to replace, but that list is growing too fast these days.

Definitely sounds like your heater core needs to come out. As OldGuy said, flushing helps for a little while but ultimately the core will get clogged again. Thankfully, replacing the core itself is not too bad from what I have researched.

Check out this write up on replacing: Heater Core DIY

yea, ive read through that a couple times. doesnt seem too bad. especially after doing the steering rack. my clutch is going bad now too...ive never tackled that one, the one i have in now i paid a shop to do 6 years ago but now im going to have to ask someone to help out with that. Cash is harder to come by nowadays when ya grow up, get a mortgage and have a kid, lol

[n7plus1]

New here. Registered to address the OP's issue: Marginal heat at least until the car [2004 A4 1.8T] is driven at highway speeds for several minutes. I'm not qualified to work on my own car and would need to have the car serviced, whether it's flushing the coolant system and heater core if that's separate. I think that's around $200 at my local Audi dealer. My question is, what if I need to have the heater core replaced? I'll call them for a quote, but any suggestions on the cost and any other cost-effective way to address the issue or make the repair? Also, could this be a thermostat repair? What do you guys think that would cost?

And since money is tight right now, what happens if I wait (besides freezing my a$$ off)?

nothing really, youll just be cold...that i know of. the heater core is a somewhat separate system from the main coolant system.

[sa_seahawker]

Heater core only costs about $130. Don't forget to get the new seals/clamps with it too.

The hardest part about swapping the core is removing the gas pedal. Two top screws are a serious PITA. But you can get it with an elbow socket and whole lot of curse words. Then the core is behind the black cover with small gold-color screws.

Though I would recommend blowing as much out there as you can. Then I cut finger tips off a rubber kitchen glove and grabbed a couple of my daughters elastic hair tie thingies. After disconnect the pipes, I wrapped those on the pipes so I could get it out of there without having to worry about dropping too much coolant everywhere.

[n7plus1]

i read through the DIY and someone stated you didnt need to remove the pedal, it can be done without so.

Fletch, which pipe would you recommend blowing through first? Im assuming the one that would make the flow go in the opposite direction? if so, which one would that be? top vs. bottom

[old guy]

Blow through the top hose first. That would be the reverse direction.

[customa4]

Damn OG in stealth mode with the reply in 4 minutes.

[sa_seahawker]

Damn OG in stealth mode with the reply in 4 minutes.

Funny how the term "OG" has the double meaning g of "old guy" and "original gangsta"...

PERSONAL UPDATE: I had been having same problem as o.p. I've swapped water pump, t-stat, two rear flanges, two hoses, three reservoirs, two caps, and a heater core two days ago....same problem...

My only theory is that the t-stat is somehow stuck open?

[caldy315]

Failing water pump? like the impeller blades are are all gone? or it stopped spinning? I don't quite picture this.

I've heard of this before on other car forums. If your WP is older, the thought it due to impurities and junk in your coolant, the impeller blades get worn and lose length. Therefore it takes more RPMs of the motor to push more coolant all the way to the heater core. Made sense in my mind. I doubt this is the OP problem though with a 20k water pump.

There is this thing to, specifically meant to blow the junk out of heater cores. Looks like a nice tool to have.
http://www.amazon.com/OTC-6043-Blast...vglnk-c1005-20

[n7plus1]

Funny how the term "OG" has the double meaning g of "old guy" and "original gangsta"...

PERSONAL UPDATE: I had been having same problem as o.p. I've swapped water pump, t-stat, two rear flanges, two hoses, three reservoirs, two caps, and a heater core two days ago....same problem...

My only theory is that the t-stat is somehow stuck open?

due to your username and the fact that San Francisco should be in the super bowl instead and that ive wanted to punch richard sherman in the face all year, i can only say that i wish you continue to have this problem. lol :P

[n7plus1]

Blow through the top hose first. That would be the reverse direction.

thanks man...i have a completely serious question though. If I do my clutch at some point this year what could i offer you if i were ask you to give me a hand?

[oaybar007]

My comment about being in the same boat is an understatement, Nate. Current urgent repairs on my 04 USP, steering rack, clutch and heater core!

Also needed, motor mounts, control arms and new springs/shocks. I've been barely driving my Audi in favor of my Subaru Forester, which is a tank of a little SUV, for the better part of two years. I refuse to shell out money for shop time on the Audi right now for the same reasons you mentioned. House, etc. On the flip side, spring is right around the corner and I want to enjoy the car again.

[n7plus1]

ive done the steering rack, control arms and springs/shocks...3 of the most time consuming, stressful repairs. sorry bud.

[old guy]

thanks man...i have a completely serious question though. If I do my clutch at some point this year what could i offer you if i were ask you to give me a hand?

I would probably need a new wife. Between long work hours and the time I spend on AZ I don't think she would be too happy with me

[n7plus1]

psh, she doesnt seem to be very supportive :(

[sa_seahawker]

due to your username and the fact that San Francisco should be in the super bowl instead and that ive wanted to punch richard sherman in the face all year, i can only say that i wish you continue to have this problem. lol :P

LoL...you can't come at me with a sorry thermostat like "Crabheat"! Dontchu ever talk about me!

Go 'Hawks!

[n7plus1]

LoL...you can't come at me with a sorry thermostat like "Crabheat"! Dontchu ever talk about me!

Go 'Hawks!

lol, wut? I like how he blamed Crabtree for making a "sorry" play but when it came down to it, Kaep threw a bad pass...

[customa4]

lol, wut? I like how he blamed Crabtree for making a "sorry" play but when it came down to it, Kaep threw a bad pass...

The worst part about that whole series of plays is that it should have been a 3 point game and that risk would not have been taken. The ball was clearly stripped at the goal line and the Seahawks shouldn't have had the ball to make it a 6 point game. Continue on....

[n7plus1]

this is true. 19 seconds left and 2 timeouts left...i wouldve waited to purposely go to the endzone on 4th down if it came down to it/the last possible play that couldve been made.

[n7plus1]

so...a little update. now that its been above freezing for a few days my heat seems to be working as it should be normally. Could it be possible that my mixture is too much water and some was frozen in the heater core without causing a burst or leak? There IS a lot of water in my mix...

[customa4]

Not the best idea to have too much water in the mix. At worst I think it's safe to have a 50/50 mix, depending on how cold it gets where you live. I'm pretty sure you can pick up a kit at a parts store that will let you know the freezing point of your coolant. If you have some coolant just pull some of the mix out with a turkey baster and add some more non-diluted coolant to the mix. Do you have a rough guess at the water to coolant ratio? I don't have access to my Bentley but I know at one point I did have a picture of the allowed mix ratios, I'll see if I can find them.

[n7plus1]

i havent the slightest clue. before i fixed a leak i was just topping off with water for a while, lmao.

[customa4]

Lol OMG! That's awful sir. I have to say the response made me laugh. I mean at this point you risk reaking havoc on the motor. When the coolant freezes it expands so that's not good. I would say you should definitely flush that coolant and got the proper mix in ASAP. I'm assuming you fixed the leak and you're not having to top off anymore?