Please expand on running too cold

[Jamie]

I have a 91 explorer 2wd 2dr, 5spd, and live in South Louisiana. My thermostat stays just above the cold level, and on the hottest day will get about to the 25% mark, I don't think I have seen it reach or stay in the middle, and never hot. With 145,000 miles, how could this affect my engine. My only concern is a machine gun sound tat-tat-tat that is pretty constant, but it too is intermittent and very hard to pin down.
What about running too cool though?

 

[Kris Guilbeaux]

If the gauge never goes off the letter C then the engine is running too cold. My Navajo did this when I bought it. The ticking noise that you hear might be your lifters. My Navajo and my moms Explorer do this too but it is not something to tear the motor apart for (even though I might)...



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Kris Guilbeaux
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http://www.tisd.net/~guilbeau/explorer.html

 

[Steve M]

Jamie,

You need to replace your thermostat, it is about $8 in parts and only 45min or so of labor, most of that will be waiting for the coolant to drain and trying to figure out how to get the bolts for the intake off. You might want to do a coolant flush and fill at the same time.

 

[Garrett]

If an engine never warms up, it can't burn as efficiently as possible - making more crap spew out the tailpipe, and getting worse performance and fuel economy at the same time. As mentioned above, change the thermostat - it's a cheap starting point to finding the problem.

And just a note on the tapping noise - I had that noise in an old '93 that's no longer mine, and the sequelae was a broken connecting rod that destroyed the engine. I had the dealer look at it for a possible lifter problem, but that problem couldn't be found. And, a couple days later, the engine froze with a bang. Just thought I'd share this painful story one more time! It helps with each telling.