Well, on the 91 5.2 auto I bought, i got the thermo replaced with the 195 degree unit - the one in it WAS a 160 - and now, the truck WILL warm up to half-way up the temp gauge - while running - if I stop, and let it idle, the temp will drop some, JUST above where it was with the 160 thermo.

Also, after swapping the thrmo, the CEL went out - and is no longer displaying, but I do have a 'Maintenence Required' light, now. What is this? I could not find reference to it in the owners manual (which seems pretty much useless)? Is it just a reminder for scheduled maint, and if so, for what, and how woudl I reset it?

 

Have you checked your fluid level. Sounds like you are low. 190 is factory. 160 will set off the CEL, just like you said. As far as I know the Maintenance light is for service reminder, like you said. To change oil and all. To rest I would guess just unplug the battery for a min or so.

 

You make me wonder now. Before I replaced my radiator and thermostat last winter, My truck would run steady right in the middle of my temp gage. After a new radiator and thermostat (what ever $6 one the local shop had) it now runs no warmer than 25% of the gage, idle or highway.

Is that running too cool? Will my heater suck this winter? Its supposed to be a bad one again!

 

Oh yea a low thermostat will lower the heater temp.

 

Lol, if you got a 180 deg thermostat, the blunt answer is yes, your heater will SUCK this winter. It probably gets a LOT colder up where you are than it does down here in NC, and last winter with my 180 deg thermo, I about froze every morning. If you turn the blower speed up past 1/2, it will cool the heater coil right off, and keeping the blower at 1/2 or lower will take forever to heat the truck up. It will eventually get comfortable in the truck as long as you have at least a half hour drive to make.

 

Huh, mine seems to heat up just fine, in the cabin and the temp guage doesnt even get past the second cold side line, because of that ive been told i could have a 180 thermistat
in the photo it isnt fully warmed but when it is it dosnt get above that line

 

Ya it looks like you got a 160 thermostat. For me 180 hits just on the 2nd line. It took me a minute for me to figure out what is wrong in that pic. It is the gas guage. I'm not use to it being that big.

 

Lol, wow, your right Crazy. The '87s sure had some differences in the dash board. I mean I know even some of the newer 1st gens didn't have a tach, but the speedometer only goes up to 85! I'd have that thing bouncing the needle off the bottom on a daily basis!! They must not have put much stock in the carbbed 3.9.

 

Ok, well, still curious - since the gauge only seems to get to the right reading while driving, and it idle it drops down to JUST above the second line on the cold side, plus there is STILL no heat from the heater, regardless of where the fan speed is at, I'm at a loss.

I will have to warm it up, and drive for a bit, and feel the heater hoses, etc... May have to back-flush the heater core...

If it comes down to it, how difficult is it to replace a heater core in one of these things?

 

Two other questions here - one is related to this, one isn't....

Today, on an extended drive, we foudn out the truck seems to be leaking coolant from between the engine and the trans. While looking, I could find no evidence of a leak higher up, and dripping down. My dad suggested may a soft-plug on the back end of the engine? Is this something common? Anyone else had this happen?

We're trying some of GM's awesome coolant system sealant tabs, and some alumaseal coolant sealant, to see if it'll make a difference.

Secondly, the oil-pressure on these trucks - is it supposed to vary depending upon engine speed? Like, at idle, is it NORMAL to drop down towards the low end of the gauge, and only move up while excelerating, or reving the engine? I have had some vehicles that ARE supposed to vary, and others that are not - I'd like to know if this is an issue I should address now - oil-pump, etc..., or not.