James R.

I made the 400 mile trek from Thousand Oaks to Santa Rosa California last nite and noticed much to my surprise that the Coolant temp needle had dipped almost back to zero while comming down the Grapevine (steep grade). I was quite alarmed to see this since I've never seen the needle move to the left so much as even a hair.

I wondered if it possibly had to do something with the fact that there was hardly any engine load...and the ambient temp was around 30 F or so. But then I started to think that despite this the Thermostat should close thus bringing the temp back into spec. Anyhow I pretty much discounted it as a fluke until I hit flat land and started to clip along on the I-5 at speeds approching 100 Mph...plenty of engine load no doubt...alas the needle began to dip down again. All the while the Oil temp was a pretty solid 200 F it's usually around 212 but I think the colder weather explains the 12 Deg difference.

Anyhow I made a call to my friend via cell and asked him to get me the location of the engine coolant temp sensor in the OBD info via the climate control. I punched it in (51 I think) and the value read a solid 90 C which is right on par with what you'd expect (is this really the address for that value on a 99 car is the question?) Anyhow it never moved so I began to feel a little more comfortable.

Eventually I decided to drop a line to Anthony Gelinas of Greedspeed and tell him what was going on. I was worried that the thermostat I used when I installed the K04 may have been defective...but he said it's actually a pretty common behavior. He claims the people seem to have this problem a lot when they drive long distances in the cold. It seemed too perfect, this was my exact situation, but I trust him so I didn't question his info.

I appeared (assuming the code on the climate control in the FAQ is the right one for a 99 A4) that the temp val the ECU was seeing was 90 C...but the gauge on the dash was all over the place...never high, but sometimes waaaaay low or perfectly straight up and down.

Anyhow has anyone else had this problem...I took a few pictures of my guages reading 80~90 Mph oil at 200 F and coolant at 0 to shove in the dealers face when they claim they can't reproduce the problem.

I wonder where the temp sensor is...if it's in the radiator maybe the thermostat closed to keep the water in the block...then the cold air dropped the temp of the water in the radiator enough for the temp needle to peg to the left...then the thermostat opened when the block water got hot enough causing the temp to move back up as the hot water moved back into the radiator...it did seem to have a period.

Thanks in Advance,

James R.

99 1.8TMS (Neuspeed K04, K&N Filter, S4 Wheel Well Liner Mod, Remus Exhaust,Neuspeed Sport Springs, Neuspeed Front Anti Sway, Bilstein Sport Shocks, Brembo Rotors, Mintex Red Box, Ronal R28's 17", Euro Corners, Clear Sides, Full Tint...and some other stuff I probably forgot)

pauls

the temp sensor has to be somewhere toward the top (or virtually at the top, plumbing could put it lower) of the engine block. The reason is b/c the cyl heads are the most sensitive and hottest points in the engine. Thus cyl head water temp is what the sensor monitors and the thermostat regulates, so these two devices are usually in very close proximity. Everything else in the engine is always cooler as water from the cyl head goes through the thermostat directly to the radiator for cooling.

Sounds like you have a wacky guage or bad connection. Although I hear some scary things about interconnection between devices on Audi's. I'd connect my heated mirrors to the rear window defogger switch but the posts I read (and the faq) indicate that things may stop working, like the temp display, if you do this. Why things should be interconnected like this is a total mystery to me!! The moral to this story is that Greedspeed may be correct especially since the ECU seems to be getting the correct temp the sensor must be OK.