BobKat

Here's a weird one for you all in line with the now old questions and topic of the so-called over-heating problem referenced here. If there's anyone out there with an answer I would surely appreciate it and it may help those who have posted what I consider to be a similar problem in this question/topic: I own a 2004 Subaru Outback, 2.5 liter H4 engine, manual transmission, CA emissions compliance. I am a former auto technician and though not an expert on the latest technology, I know a lot. The car has 220,000 highway miles on it. a few weeks ago I replaced the head-gaskets with Felpro Improved designed gaskets, timing belt and all associated parts, the clutch, rear main seal, O2 sensors (part of the problem) water pump, thermostat (Duralast fail-safe), cam and crank position sensors, spark-plug and wires and the engine temperature sensor. I commute 150 miles a day to work and the job seems to have gone well - the heads were leaking but are no longer doing so. There are no leaks. However the O2 sensor, bank 1 triggers the same OBD2 code at around 400 miles, Prior to changing the 5 O2 sensors the warning light would activate within 100 miles. The cruise control still won't stay on. And I have to very weird temperature sensor problem: As I read that a slightly malfunctioning temp sensor can result in the O2 warning, I changed it with a new one when I did all the engine work recently. It was a WELLS SU4300. There's absolutely no reason these days to rely only on Subaru parts as in most cases these parts are supplied by the very same manufacturer that sells the so called "after-market" part. Prior to the "engine rebuild" I discussed my temperature gauge start at base and gradually rise to the mid-point after warming up and stayed there. After the rebuild during which I installed a new temp sensor, I was surprised to notice the temp gauge going to the mid-point and much to my dismay climbed well past the red-line. I noticed this as I was test driving it after checking everywhere for leaks and found none. I quickly went back to my shop and parked, turned off the engine, popped the hood and looked for signs of over-heating. There were none. I hadn't driven far so I thought maybe there was a pocket preventing the thermostat from opening. I felt the lower radiator hose which seemed at first to verify my concern as it was cold in contrast to the upper hose. However the radiator fans hadn't come on - so did I have a wire unplugged? I didn't. I started the car again and the gauge went to mid-point for a couple minutes, then rapidly went over the red line. I let the car idle hoping if there was a vacuum bubble it would clear and the thermostat would open and /or the fans would run. I kept feeling the lower hose. In the time I would expect for the thermostat to open with it idling, the lower hose finally got hot indicating the thermostat opened. The fans still hadn't come on. Still no sign of over-heating. After about 15 minutes the fans came on for about a minute and stopped. The engine was not over-heating as indicated by the gauge. I turned the engine off and let it sit for about 2 hours. I then put the old temp sensor back in, started the car and all was good as I drove the car to work for about three weeks with the gauge reading normal. I got a refund on the temp sensor as it was apparently defective. Since the O2 warning still was happening around 400 miles and the cruise control still would shut-off, I ordered another new temp sensor from a different autoparts store. I got another Duralast/WELLS SU4300. I installed it yesterday and noticed that when I activated the ignition without starting the engine the temp gauge went to the mid-point immediately. The engine was stone-cold.I started the engine and within about ten minutes idling the gauge read above the red line. So two defective sensors from two separate suppliers? Same part number? I called the auto supply store told them my car and asked if the part number was correct? Only one sold for my car. I let the car cool, put the old sensor back in and it's back to the normal mid-range. So what I know: 1) Engine not over-heating. 2) WELLS SU4300 the only temp sensor available for my car. 3) Old sensor corroded and it needs to be replaced sometime. 4) All new sensors read over-heating when that's not true. What am I missing? What could be the problem??? I don't doubt the old sensor needs to be replaced, but the way the new ones act am I forced to depend on the old one forever until it decomposes?