Hi Everyone :).. I have an Audi A4 2004 and its been diagnosed with a head gasket leak.. Now unfortunately, the car won't start. Any ideas why that would be?

do your self a favor don't even bother with that head gasket sealant. the audi's engine runs to hot for it to be any real use. What you need to do is have the head torn down and replace it with an either original or after market gasket. tho i recommend getting it from audi. When it comes to the cooling system in an audi it is very important you fix it properly or you risk not having an engine at all. thats the risk with high performance engines. if this were a gmc or ford i would say go ahead do what he said and seal it but its an audi and doing a half arsed fix only causes more issues and more money spent

Yes Mr pro fixer take the car to audi have them fix it thats great wow pal. Forget that you know it all. Blue devil works for all cars I ve used it on my audi and bmw and full size truck and its been just perfectly fine just follow directions and that is your protection!

I am not saying to take the car to audi and let them fix it I am saying use genuine audi parts to repair the problem When your dealing with a blown head gasket it usually means you have a 50/50 chance at a warped head. Slapping on some sealant won't fix the internal issues as your cylinders will not have the right pressure. bad pressure no running and no amount of sealant will fix it. the head has to come off and be inspected then a new gasket used. So Mr i want to find something to harp on why not look into the full explanation before making your self look like an idiot... sound about right ?

Just a 2 cents worth; I just fixed a 1.8T in my 05 Passat with blue devil. There was no oil pressure due to coolant in the engine oil, misfires and all kinds of error codes. I changed the oil twice with short idle runs in between and changed the filter, drained old coolant then added clean water plus the blue devil. Ran for about an hour after warm up. Oil pressure is now perfect and a compression test came in at 150 Psi on all 4 cylinders. No check engine light anymore so misfire due to head gasket is gone. So though it's not the same as a new head gasket and machined head it can work. I'll drive it for 100k and see if it holds up. I do all the work on my Audi and VW cars so it's more about convenience than cost for me. Certainly worth trying if $30 is your budget not $3k (which is all the 05 Passat is worth). Happy trails.