88 90q IP done + autochk says HOT ! !

[Andrei Kogan <abk@phy.duke.edu>]

Hello fellow listers,

did the Timing belt Idler pulley yesterday. A few quick comments:
1. The main pulley has to come off to remove the Idler. Their "projections"
interfere 
(only by a few mm, but enough to prevent the IP from sliding off)

2. I used a screwdriver to pop out the old idler. however, I don't think
I'll do it again. 
It is easy enough to  make a simple puller using a screw that fits the
thread in the pulley.
It appeared to me that repeated use of screwdriver/prybar may deform the
Idler housing in the block.
I think so partly because the new one went in to easily -- I just started
it by hand, pressed *a little* and it
popped right in. 

3. I didn't drain coolant, nor did I remove the waterpump. I just loosened
it to free the timing belt. A little bit of
coolant seeped through the seal, but not much --- less 1/2 cup I'd say. I
didn't need to add any afterwards. We'll
have to see if develops a leak before another 60K.

4. The old idler pulley *WAS* about to go bad. Funny , I couldn't tell
while it was on the car -- I kept spinning it and it felt just fine, quiet,
no play, smooth etc. I almost wanted to put everything back together, but
then decided it would be foolish. So I said I hope Lonnie knows what he is
talking about and popped it out. Playing with it in my hands, I managed to
make it produce the exact same whine I used to hear from the engine. I was
VERY impressed with the mechanic who pointed that out, he was certain it
was the IP and none of the other stuff that's quite close ... 

Moral of the story: don't assume you know better, always replace everything
whenever you are there. 

Now, the question:

This morning, on my way to sears to replace the 1/2" breaker bar I
destroyed  (Fortunately, it snapped when I was tightening the pulley bolt
back ) The Autocheck system signaled a problem with coolant. Here is the
situation:

1. The in-dash coolant temp gauge behaves as usual
2. Radiator hoses get warm, so I assume that indicates that the thermostat
opens (please confirm)
3. The level in the expansion tank is at minimum mark when the car is hot (
so plenty of fluid in there)

The buzzer and the blinking water temp symbol come on for a  minute or so
shortly after I get going. then they 
seem to go away. It doesn't happen every time, but happened at least three
times today.

Can someone explain the "topology" of the cooling system to me?  I am
trying to figure out the direction of the flow, 
where all the components are along the flow -- thermostat, radiator,
engine, all the sensors.
Does anyone know what sensor feeds the autocheck system? There are two
sensors on the port on the left side, one, 2-pin unit pointing upward and
another bigger one pointing downward. I tried to unplug the 2-pin sensor
and determined that it wasn't the one for the dash --- the temp gauge in
the dash was still working, however I got the Check Engine light, so the
2-pin must be then for the fuel injection system.


Any comments? I am leaving on a 6-hour  trip to Atlanta on Friday, do you
think there is something I could/should check/do before I go?

I don't tend to trust the autocheck in our car --- it never warns about
fuel getting low, and sometimes it 
signals low oil pressure when the car is very COLD, which is not at all
what I expect based on my experience 
with the 4000 which has  an oil pressure gauge on it --- the *cold* 4000 is
*least* likely to have the oil
pressure too low, it usually is above 5 bar even when idling. But I don't
want to neglect it and feel stupid afterwards. 


Thanks a lot everyone. 
Please cc your responses to abk@phy.duke.edu  ,
as I am in the digest mode.

Andrei