Hi guys -

I'm having trouble with my 2001 A4 2.8 overheating. The other day I notice my coolant was low so I added 50/50 to the fill line. The next day when leaving work I noticed when I turned it on there was a horrible knocking sound coming from under the hood I took a look and it was dark out so I didnt really see anything. Home was only 5 mins away so I drove home and by the time I got home the sound was gone. The next morning I went out to start it up and the knocking was back (seems to only happen when the car is cold). I drove again after the car warmed up and the knocking sound was gone...after about 5 mins my temp gauge was on HOT. I pulled over and waited until it cooled down so that I could drive it back home.

Any ideas? I assume its either thermo or water pump but your input would be much appreciated.

Car details: 2001 Audi A4 104,000 miles. ( I haven't had timing belt service yet)

 

Where does the knocking sound come from? I wouldn't be so sure that the two symptoms (overheating and knocking) are related to each other. Overheating is probably from a coolant leak, since your coolant level dropped...but doing the wp and tstat w/ a coolant flush is a good maintenance step anyway at that mileage. you may also want to replace your spring clamps on the coolant hoses with some better quality hose clamps. Use Pentosin G12 coolant.
The knocking is probably just noise from the lifters when the engine is cold.

 

You should be using G12 and nothing else. If G12 mixs with any other coolant it forms a jelly like substance. This jelly could be blocking coolant flow.

 

knocking sound is hard to tell exactly where it is coming from...it almost sounds like its coming from the fan.

Could any of my problems be due to the fact that I just used regular coolant that I got from speedway and mixed it with water? Does it have to be this g12 stuff you are talking about?

 

ok, well it wasnt g12, so that could be the overheating problem...no? How should I drain what i have in there and replace it?

 

Well was your original coolant pink? If so, and you put any other coolant than you def. need to flush your system. If that is not your problem as of right now you WILL have a problem soon. Here is a write up.

http://audizine.com/forum/showthread.php?t=73219

 

mixing non-G12 compatable coolant will only do harm over a long period of time. If you keep in there for a week or 2 before you do the wp, it won't be bad. it won't turn to jelly overnight. the green coolant just is not as good at preventing the aluminum engine and cooling system components from corroding than the g12 coolant. you should be able to order everything including coolantat ecstuning.com. the dealer will charge ~$25/gal for the G12, and will charge you 3x as much for the wp, tstat and belts as ecs or 034motorsport.com.
You really gotta find where that noise is coming from though.

and you can get cheap distilled water for ~$1/gal at a riteaid or cvs pharmacy to mix 50/50.