What a day. 2002 A6 4.2.

First, the question- a coolant line failed today, it goes from a molded union at the top of the radiator hose back toward the firewall. I assume this feeds the heater core? I had to McGyver a repair at the radiator hose- what & where is the attachment at the other end? Is it serviceable from the engine compartment?

In other news..noticing erratic performance and mileage numbers, and an occasional odd response from the temp sensor, I replaced that. I also, anticipating worse news, ordered a MAF. From what I could tell, seems like the temp sensor did some good. It's an easy job..

Now, if I install the MAF I assume the Bosch will self-adapt over time, even if I don't use a VAG to run the internal adaptation process?

I'm also thinking of doing the fuel pressure regulator as a preventive measure-- 122K and climbing.. Looks like another simple plastic clip- any tips aside from depresurizing the system?

 

No coolant hoses leave the engine compartment, there are two hoses that go to the firewall yes which are the heater core lines, they stop right at the firewall behind the battery. You have to remove the battery to see them. The connect to steel lines that stick out from the firewall, the steel lines are connected to the heater core and aren't servicable unless you pull out the entire dash board.

The MAF sensor isn't needed, if you did, the engine would hardly run. I would just shelf it in anticipation that you may need it down the road. The fuel pressure regulator won't have to be changed either, but if you want to replace something for maintenance replace the upstream O2 sensors, they are only designed to last around 100k then they start to degrade. O2 sensors will cause super poor fuel economy and rough engine concerns if not serviced.

P.S Upstream O2 sensors on a 4.2L are a *****

 

Thank you! In retrospect- sorry to call you out in the subject line, poor manners on my part, I appreciate your response.
Sounds as though I can get the hose from the dealer and replace it if I can get at the connection to the steel lines. I assume it's just a pressure clamp? It split right where it entered the molded radiator hose. I was able to extract the barb that was still in the rubber hose, and have it McGyvered- but it isn't a solid repair.

I appreciate the advice on the MAF, and the regulator. Not trying to squander money, despite how it sounds.

I did try to get an estimate from an exhaust shop for O2 sensor replacement (Labor costs- I've found sources for the sensors themselves- ouch!) and they said it would be more likely that one or both cats would fail soon, and I could do them at that time.
I'm recently relocated and have no tools/garage, so under-car work isn't an option.
Again, thanks
ST

 

Just PM me next time, i have a massive PM box just for that reason.
Most of the coolant lines are secured with simple adjustable clamps that usually require a special type of plier to get them off, you can use needle nose pliers as well, just takes a little more effort. The cats probably won't fail unless the engine isn't taken car of, like lets say the O2 sensors, coil packs, spark plugs, vacuum hoses blah blah.