1/4 scale

Today I had a problem with my cooling system. Low coolant display was flashing in the instrument cluster while driving on the highway. Temp gauge is near the red mark over on the right side of the gauge. I pulled off and popped the hood. The expansion tank is way below the min. mark. Coolant below the tank (exited the relief valve). No other signs of coolant or ruptured hoses. The engine was idling while I checked this and a quick glance at the temp gauge again showed a normal temperature reading. I topped the tank off with water and started to drive again, and the temp needle quickly swung back to the 3/4 mark. I promptly turned for home and made it back by coasting with the engine in frequent idle mode. Idling seemed to keep the mark in the 3/4 zone on the gauge.

So what do you guys think it is? I haven't changed the coolant sensor (G62), but from what I understand, a faulty one doesn't result in an overheated engine (mostly odd temp gauge readings). My next thought is the water pump, with impeller spinning (or not spinning on shaft at high engine speeds), hence normal gauge temps at idle. The other obvious one is the electronic thermostat (stuck closed or near closed). Other problems could be a bad coolant tank or cap which is (are) not pressurizing the system correctly.

I haven't replaced any of these parts yet. I guess the first part to change is the temp sensor, then move on to the water pump and thermostat (may as well do the timing belt as well in that instance). The engine is an 02 1.8T with 60,000mi. Anyone have any experience with similar symptoms? Thanks.

diagnosticator1

Sounds like you will be doing the TB now also. Be sure to get the TB Kit, it will come with a coolant pump. Check out ECS Tuning or similar.

1/4 scale

any good cheap online sources for the oem thermostat?

Bronze

ecs sells the OEM thermostat separately, IIRC.

1/4 scale

Yes, I saw it there as well. I decided to go with Jim at DieselGeek. Bought the entire TB kit for $299 shipped (OEM thermostat included). Here's the list of parts I'll be getting this week:

2002-2005 B6 Audi A4 AMB 1.8T T-belt kit:

06B109243B Timing Belt Tensioner same as OE

06B109477A T-Belt Tensioner Damper w/244 roller same as OE

06B109119F Timing Belt Contitech same as OE

06A121011L Gasoline Water Pump Graf-metal impeller

06B121111H Thermostat/housing OE complete plastic unit with o-rings

06B903137C Multi-rib belt, Conti same as OE

026103085D DPH Cam Seal better than OE

.8C120HCS 8mm x 120mm black hex cap bolts

H20 Extractor bolts

Contact Jim at jim@dieselgeek.com if you're interested. He use to have a kit on his website but took it down since ECS and Pure probably had the sales market (he's mostly a diesel parts VW/Audi business).

Bronze

Thanks for the info. I'll be doing a TB change probably around August.