350 Chevy operating temp

[Bulldog]

I'm sure Kevin can answer this one, but please feel free to chime in.

I am trying to get my 1987 Chevy 1/2 ton ready for my son to drive. Everything operates well, but the engine doesn't heat up much when it's really cold. I haven't driven older vehicles in awhile, but I don't remember them being so cold blooded.

I installed a 195* thermostat earlier this summer. I operated fine and I could see the thermostat open up at about 195*. Once it started getting cold this winter, the truck would run about 150* even when parked. I put some cardboard in front of the radiator, but it didn't seem to help. I think the thermostat was sticking open, so I changed the thermostat again. The thermostat opened at about 195* as it should and the heater seemed to blow fairly hot air. Now at -40* the engine temp may be only getting to 150* when parked and about 135* when driving. Not very warm in the cab either. I don't want to believe the thermostat is sticking open again. Any suggestions? I was thinking of putting some pipe insulation on the heater core hoses since these are fairly long and could be losing a fair amount of heat in the system.

By the way, the truck has a after-market flex-fan and not a clutch type fan. Could the flex fan be moving too much air cooling the system? Do you think a clutch fan would work better in the cold?

If I need to replace the thermostat again, I may go with a 205* thermostat. The guy at NAPA said he did not recommend these with computer controlled vehicles because the higher temps may be misinterpeted by the computer as an overtemp condition. My 1987 truck is the first year of TBI fuel injection, I don't know is the computer is complex enough that a 205* thermostat will affect it

[arcticmutt]

check the temp going into the heater core and then the one coming out see if they feel about the same if not you may have a plugged heater core or air in the lines if you think that it may be air remove the radiator cap and high idle the truck to bring the temp up then when the thermostat opens the level should drop when it does fill it up and put the cap back on and see if that helps any

[Angler]

when the turd's fan met Mr. Optima it was -20 and I wheeled for about an hour and then drove all the way back to fbx from Np and the temp never got abve where it usually is at operating temp and that is with no fan!

[ChevyKev]

I dunno ... if you have the front blocked off, it shouldn't be that bigf of a problem - but I would attribute most of this go round to -40 temps.

Mine seems to do ok, but I don't have a temp degree guage, just lines and a red bar. My heater hasn't hbeen blasting hot air, but the cab is comfortable. hrug:

[99TJ]

Like Kevin said I'd say it was the cold temps if the front is not blocked off. My 82 would run around 180 sinc I had a 180 thermostat in it

[4x4_MMMH_4x4]

heehee mine runs at 200 but i dont get comfortable heat:whistle:

[akdsmer]

-Interior cab heat is a product of the exchange of cold outside air and hot coolant. You don't get much better than 150* at the vents with 195* and shop air, you can bet that 100* air out the vents is only warm when you have -40 air pushing through the core. If you drop the engine temperature down to 150*, you will be lucky to anywhere near that with a good heater core.

-A fan pushing -40* air onto the engine is a very good heat exchanger. I would replace the fan with the correct fan. Most likely this will fix your problem. Same thing happens when the thermostatic clutch fans go bad.
I would remove the fan and see if the engine will then maintain temperature. If it doesn't, then replace the thermostat. I don't buy my t-stats from the aftermarket. I get them from the dealer. Even then you can get bad ones-a typical failure is a bad spring that won't keep the valve closed, or an aftermarket pump/pulley that has higher volume/pressure than stock.

-It doesn't take a sophisticated computer to see that the engine temperature is getting too hot and then pull timing and add fuel (to cool the cylinders). But this doesn't happen at 205*. The only real computer issue is that many times a 160* t-stat will keep the vehicle from going into closed loop on pre 1996 engines, as it is waiting for it to warm up. this also throws codes on FI vehicles for not reaching operating temperature.Regardless of the temp of the t-stat, it is suppose to keep the engine at the set temperature, so keep the 195 that came with it and ditch the cheesy fan.

I've had a couple of early 90's TBI trucks. They all made good heat and kept at or near operating temperatures when it was cold, although one wanted a few more rpms to flow enough coolant through the core to make great heat.

[Bulldog]

OK, now I feel a little dumb. The first time I blocked off the radiator I only loosened the fan shroud and inserted cardboard. Upon closer inspection, to get the cardboard between the radiator hold downs; I only had covered 70% to 80% of the radiator. Before I changed out the fan, I decided to cover 100% of the radiator. I removed the radiator hold downs and leaned the radiator and shroud back allowing be full access. I used some reflective foil insulation to cover the entire radiator. After a little test drive, the engine was running at 210* (insturment cluster guage) and I even saw 215* at one point. The cab heat is decent now considering it's -30* outside.

[Bulldog]

OK, covering 100% of the radiator didn't fix it. Two different trips in town and it's only running 150* now. Looks like the thermostat is sticking open. I'll take Kelly's advice and buy an OEM therostat, not an aftermarket. I'm getting tired of changing t-stats.

[AKMark]

Another thing to consider would be getting rid of mechanical fans, and buying a Taurus electric fan setup. That way nothing would pull air at all until it was switched on which in the winter, you probably wouldn't need to run at all.

BTW, no vehicle I owned (and I had several) ever got to normal operating temp during the -40's up there. I'm sure a few folks remember Michael who had a Durango who's 360 wouldn't give heat when it was below -25, no matter what he tried.

My 85 Burb would get close with the high idle on for extended periods of time, but the moment I started driving the temp would go down.

Try removing the fan shroud when you are playing with it. That will decrease the amount of air pulled by the fan. Just watch in the summer as you might have an issue keeping your cool, but it should be fine.

[arcticmutt]

with my full size dodge and no cardboard at all I run 205 to 210 even at 40 below

[Bulldog]

Chevrolet/Cadillac of Fairbanks (Lithia) and Aurora Motors were both out of themostats. GT Automotive supposed carries AC Delco also, but they were closed today. All the parts stores in Fairbanks only sell Stant, which I've already installed two of these and they both seem to be sticking open. Yesterday, the engine temp did warm up to where is was suppose to be running for a short period so I know the engine should run warmer.

Maybe I have some junk in the coolant system that could be causing the thermostats to stick open. I installed new coolant after installing the thermostat, but maybe the system needs to be flushed. Is there a good way to do this in my garage without making a mess? Or should I just go to a shop? Any recommendations of a good shop? Do they just back flush the system or perform something like an acid flush?

[78calico]

Before you go out of your mind, try heating up some water in a pan on the stove. Throw your thermostats in along with a thermometer and watch what happens. It's a quick and easy way to verify if your thermostat is actually opening and at what temperature. The temperature warmed up above -20 yesterday.

[akdsmer]

I'm sure a few folks remember Michael who had a Durango who's 360 wouldn't give heat when it was below -25, no matter what he tried.

He had a bad heater core. He was too cheap to replace it.

FYI My 1.6L sidekick came up to temperature and was blowing rather hot air at -35*.

[AKMark]

He had a bad heater core. He was too cheap to replace it.

FYI My 1.6L sidekick came up to temperature and was blowing rather hot air at -35*.

I helped him change it, it still had no heat when the temps dropped below -20. I even helped change the radiator and water pump. That stupid truck wouldn't warm up period.

[justimpact]

I have a tool that pulls a vacuum on the cooling sys. when refilling with coolant this prevents any air being traped in the cooling sys. which may cause no or insuficent heat it also fills the cooling sys. faster and without making a mess if you are intrested in flushing the cooling sys. let me know all that you need is a few 5 Gal. buckets cooling sys. flush additive a garden hose and some time

[akdsmer]

I have a tool that pulls a vacuum on the cooling sys. when refilling with coolant this prevents any air being traped in the cooling sys. which may cause no or insuficent heat it also fills the cooling sys. faster and without making a mess if you are intrested in flushing the cooling sys. let me know all that you need is a few 5 Gal. buckets cooling sys. flush additive a garden hose and some time

AIRLIFT. I have one as well. It is great for pulling a vacuum to verify that the system is leakproof before installing the coolant.

[justimpact]

AIRLIFT. I have one as well. It is great for pulling a vacuum to verify that the system is leakproof before installing the coolant.

Yes it is good for checking the sys. for leaks but does not always work I have had several vehicles hold a vacuum but when cooling sys. is full and under pressure have leaked but for the most part it was human error or a freak of nature the vacuum leak test is acutaly one of fords aproved methods of testing EGR coolers on the 6.0L diesels