B8 S4 Mystery Coolant Leak

[ken_bunker]

driver's side
below exhaust manifold
Dripping from motor mount bracket bolt, circled.

Does not appear to be the pcv, waterpump, or thermostat. No coolant in the valley.
It has the updated waterpump.
Ideas?


2010 S4 dsg
IMG_1377.jpg

[whiped]

From the bottom of the coolant Res.

Give it a wiggle and it will usually stop. Mine does this sometimes when I change plugs.

[ken_bunker]

From the bottom of the coolant Res.

Give it a wiggle and it will usually stop. Mine does this sometimes when I change plugs.

The reservoir doesn’t appear to be leaking at the bottom. Would that drop down the side of the block?


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[Allan691]

“Give it a wiggle and it will usually stop.” LOL


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[whiped]

Mine would leak from the bottom of the tube coming out, run down the frame rail, over the engine mount and pool near where yours is.

[ken_bunker]

Mine would leak from the bottom of the tube coming out, run down the frame rail, over the engine mount and pool near where yours is.

Strange. I gave it a new o-ring there and it didn’t leak for almost a week. Seems like it’s just lined up properly or something


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[JoeCS4]

I just changed my spark plugs yesterday and noticed a minor Leak from the water hose(part number:8K0121109AB) that connects to the coolant expansion tank as well. I think I might move the coolant expansion tank too much when I do the driver side plugs, so the hose cracked? However it somehow stopped this morning.

[chilort]

From the bottom of the coolant Res.

Give it a wiggle and it will usually stop. Mine does this sometimes when I change plugs.

I just changed my spark plugs yesterday and noticed a minor Leak from the water hose(part number:8K0121109AB) that connects to the coolant expansion tank as well. I think I might move the coolant expansion tank too much when I do the driver side plugs, so the hose cracked? However it somehow stopped this morning.

Glad I'm not the only one. Only seems to leak when I've got it pushed out of the way to do the plugs.

[cgnorthstar]

Same thing when I changed my plugs. Think the bottom hose has to be on there just right so it doesn’t leak. After I put the tank back, no more leaky....lol


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[JoeCS4]

Yeah it actually leak all day yesterday. I got home last night and parked the car in the garage. After 2 hours, I open the hood and see 2 drops of coolant right under the water hose. I removed the two bolts that hold the expansion tank and pulled the tank off from frame then put it back in. In this way, I can re-lineup the tank to the frame perfectly. I haven’t driven the car since then, but I checked it like 5 times today, luckily no leak so far. I’m gonna drive the S4 later tonight and see if it holds.

[JoeCS4]

Update: still leaks a couple drops every time I drive the car. Not too terrible though.
Edit: 3/12/19 took the tow bolts that hold the coolant expansion tank out, moved the expansion tank away then put it back, no more leaks. Thank god

[ken_bunker]

Update: Found the main coolant leak... Cracked block @ passenger side engine mount bracket.

[Mira250f]

i have same problem :( , what you solution your crackle? replace engine?

[Morritse]

This just happened to me. Any resources on fixing it? If you welded it did it simply fail again?

[Bartlett]

3 people with a crack in the same area?

[Morritse]

3 people with a crack in the same area?

Seems so.

[Waffles_s4]

What year each of you with the problem is your s4?

OP is a 2010


I wonder if it's a specific year or mount part number that's causing all this.

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[Morritse]

What year each of you with the problem is your s4?

OP is a 2010


I wonder if it's a specific year or mount part number that's causing all this.

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2011

[Waffles_s4]

I wonder if the newer engine mounts have a different part number

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[Mira250f]

i have 2013 s4 :(

[B8S4OZ]

Mine is a 2010 and I just had the same issue. Replacing plugs and it started leaking pretty badly. I can see its coming from the hose at the bottom. 8K0121109AB I just quickly removed it and reattached it while losing some coolant. I will let it sit and dry out then pressure test it again.