coolant reservoir top off results in leak out of back of engine?

[mangusset]

i'm baffled. had a low coolant light come on while driving, got home before the needle moved past half way.

noticed a small trail of coolant wetting drive way.

topped off reservoir and all the coolant that was added came gushing out the back of the motor. dropped right over the driver's side cv joint.

it's tight over the top, rear of the engine bay (against firewall) to see if any coolant lines split or disconnected. from underneath, 1 line seems a little suspect but impossible to get to.

calling all gurus! thanks guys.

[mangusset]

this is interesting

http://www.audizine.com/forum/showth...a-coolant-line

[2004B6S4]

There is a coolant hose that goes from the back of the motor to the heater core. I removed my motor recently and the brittle connection on the end broke, and I can tell by the residue that it had been slightly leaking for some time. That could be your problem. (btw, does anyone know if there's a way to get just that plastic connector piece on the ends of the coolant hoses? that's the part that always fails ime and the hoses are still fine. audi doesn't sell the connectors separately). Sorry I have no idea how to replace that hose without pulling the engine but just throwing that out there as one possible cause

[924Carrera]

There is a long line that goes from the upper radiator hose, wraps around behind the engine along the firewall, tees near the middle and connects to the back of the engine near the intake, and then continues to the reservoir. It has a section of small diameter stiff plastic that cracked and was leaking on mine. When I removed it to replace it, a ton of coolant came out of the engine from that back port. Might be worth checking that one.

[evildsmr]

There is a coolant hose that goes from the back of the motor to the heater core. I removed my motor recently and the brittle connection on the end broke, and I can tell by the residue that it had been slightly leaking for some time. That could be your problem. (btw, does anyone know if there's a way to get just that plastic connector piece on the ends of the coolant hoses? that's the part that always fails ime and the hoses are still fine. audi doesn't sell the connectors separately). Sorry I have no idea how to replace that hose without pulling the engine but just throwing that out there as one possible cause

If I remember correctly someone posted before that they found just the plastic connector and tried using that to replace the failed one and he still experienced leaking. The plastic connector is only available for the TT through gap. I suggested just buying the whole hose which is only $80 from jhm of not cheaper through gap.

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[mangusset]

Guess that 'T' would be #37, it looks fine on my car

[mangusset]

and connects to the back of the engine near the intake, and then continues to the reservoir. It has a section of small diameter stiff plastic that cracked and was leaking on mine.

Thank you, what's the best way to access this section of the coolant line?

[2004B6S4]

If I remember correctly someone posted before that they found just the plastic connector and tried using that to replace the failed one and he still experienced leaking. The plastic connector is only available for the TT through gap. I suggested just buying the whole hose which is only $80 from jhm of not cheaper through gap.

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Interesting. I saw one somewhere for sale that I think was listed for the B5, but it might have been the one for the TT or maybe it fits both. I figured our coolant flanges must not be the same size, but thought about trying it out just to see for sure. I decided not to waste the money but was wondering if anyone else may have tried it so thanks for letting me know! I'm guessing it leaked because the inner diameter was a little too big and the o-ring couldn't seal?
Some aftermarket parts company should sell just the connectors. it seems like a bad design, the plastic parts of the hose assemblies are always failing far sooner than the hoses themselves. should've just used barbed flanges and clamped the hoses directly on.

Guess that 'T' would be #37, it looks fine on my car

I've heard that the coolant temp sensor commonly leaks as well, it's on the back of the engine and is marked #49 there. I'm not sure if it could have as big a leak as what it sounds like you are describing, but it's something to check. also, 924carrera had a much better suggestion than me, I wasn't really thinking things through but if it comes out right after you add it to the tank then it's probably something along that line that goes to part #37. if not the tee then maybe the hoses. did you pour in some more water and try to watch it as it leaks out?

[924Carrera]

Thank you, what's the best way to access this section of the coolant line?

It's routed along the firewall above the ECU harness. It's not too hard to access. The part with the hard plastic starts near the middle of the engine on the passenger side and continues as far as that tee. On the diagram there the line as an assembly is number 35. The brittle part that breaks is shown there like a separate piece, but has no number callout and cannot be bought separately. It goes between items 6 and 36 on that diagram.

[mangusset]

finally had some time to get back in the garage.

removed the expansion tank and found this right below the oil filter housing. it appears to be # 46 above and houses the temp sensor (2004b6s4 was on the right path). due to the lack of space, I cant figure out for the life of me how to go about pushing the hose back in. what's more, looks like it's got a crimp-on style clamp;

[2004B6S4]

the crimp on style clamp is just to connect the hose to the plastic flange. The plastic flange is broken, in your 2nd pic you can see part of it still attached to the coolant pipe and the rest of it is clamped inside the hose. you have to replace the whole hose because the plastic connector isn't sold separately. the hose is part # 8e1819371q (well it was for my car, I just replaced it less than a week ago. have your supplier double check your vin in case the part changed, though). If you have enough room to reach your hand in there to remove the broken connector, you may be able to change out the hose without removing anything else besides the battery. The plastic connector works just like the 2 radiator hoses - you gotta remove a metal clip first and then it will pull off. The opposite end of the hose goes up through a rubber grommet into the battery area, and connects to a heater pipe at the firewall just to the right of the battery.

[mangusset]

thank you very much 2004B6S4

my hands won't fit in there unfortunately

did you replace the hose yourself? if a shop did it, what'd they charge you?

[2004B6S4]

I did it myself with the engine out

[mangusset]

I did it myself with the engine out

thanks.

I was able to jimmy up an extended pick and removed the clip but can't get the connector to pull off. does it twist off or just pull straight off?

[icanfly]

It pulls straight off. but will be tight and thus tuff. There is also a small plastic ring in addition to the gasket, don't loose this. Also, try not to take that ring out. It's a complete pain to get back in. In the even that you do, remember that the bevel faces the motor...it's equally difficult to put it back in.