the mutli-MALfunction sensor strikes again!

Phil Rose pjrose at
Mon Feb 11 15:12:29 EST 2002

Yesterday I happened to pull out my boost gauge (I keep it in the
glovebox) to check max boost. The boost hadn't seemed very impressive
lately, and so I wondered if I just was getting too blasé about the
usual 17 psi from my chipped ECU, or what? Well the tale of the gauge
was that boost was down to about 11 psi, max!!! No wonder things had
begun to feel so unimpressive, by seat-of-pants.

I did a quick check of hoses and clamp connections and found nothing
was obviously amiss. Then I recalled something puzzling had been
happening (from time to time) over the past 5 or 6 weeks. About every
20 or 30 miles of driving I would see--for no apparent reason--the
"engine coolant level" warning  display go on for a few seconds (5 or
10 seconds). But coolant level was always OK. I decided that this
must be caused by a bad sensor in the coolant reservoir (overflow
tank). Then I thought: isn't that same warning symbol also used for
"engine overheating" (answer is Yes)? However no overheating was
actually happening either. But this got me thinking about the
multifunction thermo sensor.  I recalled Scott M's site had a nice
discussion about loss of boost caused by _erroneous_
engine-overheating signals from that !*$&#@!  sensor, and it's been
mentioned on this list as a potential boost-killer a number of times.

When I pulled back the sensor's rubber boot, a flood of coolant
poured out. The boot--and the electrical connector--was FULL of
coolant. I removed the connector and dried out its innards (gave it a
bath of rubbing alcohol). Then I took the car out for a test drive
with the sensor disconnected, and vaVOOOM!!! I wonder how I could
ever have taken so long to realize how seriously the boost had
fallen. I haven't yet determined if that seepage of coolant is
internal to the sensor (requiring its replacement) or just external.
The coolant temp gauge had been working reliably all this time. To
allow for drainage in the future, I will definitely cut away the
rubber boot, which is a big part of the problem. Nice to have 17 psi


Phil Rose				Rochester, NY
'91 200q	(130 Kmiles, Lago blue)
'91 200q   (57 Kmiles, Tornado red)
	mailto:pjrose at

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