I get terrible gas mileage on my 1996 A4 2.8 (10 mpg1). Wanted to change the Engine Coolant Sensor today (Autozone does NOT have the black square 4 blade sensor, only green, oval, 4 pin).

Removed the valve cover vent hose (black, corrugated plastic, coming out of the rear of each valve cover).

Full of white slimy slime (and water?).

What is that indicative of?
Running filthy rich?
Plugged cats?
Bad PCV valve?
Or bad engine temp sensor causing rich and cold mix, causing the slime (and water/condensate?) No coolant loss.

 

This sort of thing can happen if you frequently run the car for short periods of time so that the oil never gets up to temp. Also, the PCV hoses being damaged probably kept any significant vacuum from developing in the valve covers. Without the vacuum, condensation has nowhere to go.

If I were in your situation, I would replace all of the PCV hoses and valve as well as removing and cleaning the valve covers. Then change your oil.

 

That white slime is normal especially in cold weather climates. I would replace the tube due to it being cracked.
As far as getting a coolant temp sensor from Autoblown , Don't! get a dealer coolant temp sensor only! They are only about $25 , also get the plastic clip that holds it in place & the o-ring that seals it.

 

Is the PCV valve the Y valve on the driver side? One hose going to the front of engine (recirculating the fumes into the intake in the front?), 2 other going to the back (one going into the valve cover hose)?

Where is vacuum connecting to those lines?
Where are the valve breather hoses going to?

What is causing 10 mpg fuel mileage? I can understand a few mpg drop, but double the fuel consumption?

Engine coolant sensor causing ECU to stay in "cold start" (I assume extremely rich) mode? Partially also causing the slime?

 

The engine constantly thinking it's cold will contribute to poor mileage. Also, the loss of vacuum through the PCV system can contribute to this.

I think that the Y-shaped part you speak of is called the "suction pump". I'm not real familiar with the 12V engines. There is a separate PCV valve. I'll look through my Haynes Manual to see if there is a diagram of the hoses.

Even though mine is currently functional (knock on wood) I plan to clean it out/replace parts this summer. Rather than buying the same crappy corrugated plastic hoses, I plan to replace them with silicone hose. There is a writeup somewhere with a person who used heater hose. Buying the kit from ECS or the like can be costly and doesn't seem to last long.

 

bshusted, if you come across the 'replace corrugated with rubber hose' write link, please send/post.

I broke the one on the 2.8 twice already (today again), and did the same on my 2.7T. So I REALLY want to get rid of those brittle hoses (and I hate the 'mouthwash cap' connectors; never seem to get them off easy, no matter how hard I pry).

Those "Y" (suction Y) seem to be one way valves. Is there a real PCV somewhere in this system?

 

I'm thinking there is also a possibility that the Engine Coolant Sensor is sensing just fine and that the thermostat is stuck open thus keeping the engine far from an optimal operating temperature.

 

Prying? What are you prying? I find that if I simply squeeze the outer ring the entire connector easily slides off; no prying involved. Am I missing something?

 

shipo - your doing it right squeeze and it come rights off, or should at least.

vtraudt - to replace them with rubber just run the same diameter rubber hose, maybe use some fittings, some tubing clamps. I did it on mine, it wasn't hard.

 

This is easy to verify by checking the hoses at the radiator: if they stay cold while other coolant hoses already warm up: thermostat closed

Timing belt with pump, thermostat, etc. was done ca. 5k miles ago.