When I witnessed the check engine light on my 2000 Echo, I looked under the hood and discovered a 1/2 inch hose was disconnected from the air filter area. In other words, the hose actually goes back to a regulator and the wall of the car behind the engine but it was disconnecting from the air filter area of the car - towards the front of the car.
For several months I tried to put the hose back on with the existing clamp. It seemed to occur most often during hot weather and when I turned on the air conditioner. For several months I had to check this hose to make sure it didn't fall off because the check engine light will NOT come on immediately when this hose comes off. Recently, I used a non-standard hose clamp - the kind that screws on instead of the standard one that pinches on. Hopefully this won't cause more problems than I know what to deal with.
Outside of this hose problem here are other unrelated problems I experienced and fixed so far:
1) Hose coming loose from air filter area and check engine light coming on
2) Blower 2 relay failure (symptom: only high fan speed works inside car)
3) Water pump replacement
Water pump failure symptoms: rattle and squeaks under hood, serpentine belt unraveled and car began to overheat (red radiator light above blue radiator light started blinking)
Resolution: Stopped driving the car but added water to get it home to minimize damage. The old water pump will continue pump water but the bearing seals will leak fluids on the serpentine belt and the belt that goes to the power steering pump.
Tips and Tricks: These are obviously non-standard tricks of the trade but in order to get the water pump out you have to remove the alternator.
To drain the radiator completely, loosed the plastic radiator drain plug on the bottom side of the radiator. A wrench was not required for this and it can be done my hand unless someone really cranked on it.
To remove the alterantor you must loosen the bolt below the alternator and remove the two nuts on the slide aduster above the alternator, give the belt some slack and remove the belt. After removing the belt, remove the bolt below the alternator. Remove all the wires on the alternator. Thee's two hex head bolts and two plastic covers that must be removed. I was able to salvage both plastic connectors and I recommend this. Unfortunately one of the plastic locking tabs broke on one of the plastic covers but I ended using a spray on, non-permanent glue to put it back on and hold it after I replaced the water pump. Wiggle the alternator forward and backward while pulling upward until the alternator comes off completely. After removing the alternator from the engine compartment, gently set it aside for reuse. Next begin remove the four hex head bolts on the water pump pullet. The pulley must be stabilized by sticking a screwdriver threw the holes of the pulley and using the side wall of the engine compartment to keep it from turning while loosening and removing the bolts from the pulley. Next, beging removing the two nuts and three bolts from the water pump. The next steps are definitely non-standard but it worked for me. I did not worry about damaging the old water pump because it was very obvious the bearings were bad and I had a new water pump ready for installation.
To remove the water pump, you must first remove the wires attached to the sidewall/wheel well. There's two thick bolts and a locking bracket that can be removed to move these wires out of the way. Next, begin removing the water pump. Try to work the water pump toward the front the vehicle. Don't give up! I almost did because it is a very difficult task to remove it. The trick was to angle the back of the waterpump towards the front of the engine compartment and gently wiggle it back and forth until it came out. When you are on the right track you will notice the back of the water pump will lift up and out of the engine compartment. Wallah! You got it! Go have a drink and relax because you are half way there.
I'm sure my next steps will bring a lot of controversey here but if you know of a better way to get the little booger of a water pump back in, let's hear it! I put the gasket on the engine first. Next, I used a wheel grinder to grind the front and back of the new water pump shaft (ouch) by about 1/64" on each end. The grinding wheel didn't touch the bearing seals or the water pump impeller blades so I believe this is a safe method to use. This allows the water pump to go in without damaging the water pump impeller blades or the new water pump gasket that was installed.
The rest is self explanatory - put all the nuts and bolts back on the water pump - stagger the tightening of the nuts and bolts of the water pump to ensure an even seal on the gasket. Put the water pump pulley back on using the same screwdriver and wrenches you used to get it off. Replace the wire on the sidewall (wheel well side). Out the alternator back on and wiggle it back and forth until the lower bolt can be inserted. Continue wiggling the alternator while screwing the lower bolt in. This can't be done by hand - it will become too tight and you will need the wrench to get it back on semi-tight. After you get the lower bolt on semi-tight you can put the upper adjustment slide, nut and lock back on. Put the serpentine belt back on - the belt only rubs against the water pump and completely encircles the air conditioner pulley, the fly wheel pulley and the alternator pulley. Use a wrench or pipe to pry the against the whole alternator and tighten the belt. NOTE: Do not Rambo the alternator and overtighten the belt. This will just cause damage to all the bearings on all of the pulleys. The belt only needs to be tight with no slack between the alternator and the water pump. Tighten the bolts all around the alterantor, replace the wires and refill the radiator and the reservoir with 50/50 antifreeze. I used premixed anti-freeze but of course Toyota will tell you only to buy the red stuff from their parts deparment. Your choice. I don't think it matters. Toyota will also tell you not to follow my instructions but those of you who have had to survive like me and get by the best you can will understand that the dealer's advice is not always to your benefit.
Good luck and feel free to Email me! I think the Echo will be one of the last gas fueled vehicles on the road because it is so economical and still has the toyota quality engineering. I look forward to American made hybrid SUV's, pickups and cars but this Toyota will remain in the family for quite some time.
By the way, I hope GM stays in business because I wuv my Silverado pickup too.