2 Problems - Engine Not Warming Up To Operating Temperature

[Craig]

I have a 1994 GMC Yukon. Engine is a L31R crate (based on 96+ vortec) that is stock aside from aluminum intake and headers. I live in Canada where it's normal to get -30 c / -22 f.

I'm having a hard time getting it up to operating temperature in the winter. It seems to want to stay around 140-160 degrees. I went on the highway for a couple of hours and the engine was unable to warm the transmission properly so the torque convertor wasn't kicking in. I ended up getting 10.5 mpg on the highway at 2600rpm. I do have 3:73 gears in the rear, but in the summer, it will kick down to about 2100-2200rpm and give me 14-16mpg on the highway. Everything in the cooling system is new and stock with the exception of a ac delco high flow water pump. I hate to run it that cold due to the premature wear that occurs. I know these old vortec based engines like to run in the 190-210 range.

I replaced the thermostat with a expensive oem one today rated at 195 but it seems to have not done much. Is there anything else I can do to help get the temperature up? I'm thinking of buying a grille cover, not sure where a good place is to get one for a 1994. Any suggestions appreciated.

Secondly, on the highway, I noticed a fair amount of cold air coming in from the passenger side when it was on defrost. It stopped when I put it on recirculate. It almost felt like there was cold air coming from inside the glove box when I opened it up. Otherwise everything is working fine. Could it be a faulty blend door?

Any suggestions with these quirks would be much appreciated. Thanks guys!

 

[454cid]

Have you verified the engines temperature? The gauges are not precise. Mine reads a little high, but I've seen them run low like you've described, too. I would use an IR gun, or at the least use a scanner and see what the PCM thinks the temperature is.... I think the TBI engines have two sensors like the Vortec engines and I doubt both would be bad.

A grill cover is as close as your nearest cardboard box that you don't need...that's what I use when I've wanted to restrict cooling. Just don't forget it when it starts to warm up, and don't cut it too short or you won't be able to easily get it out from between your radiator and core support or whatever.

 

[Craig]

Have you verified the engines temperature? The gauges are not precise. Mine reads a little high, but I've seen them run low like you've described, too. I would use an IR gun, or at the least use a scanner and see what the PCM thinks the temperature is.... I think the TBI engines have two sensors like the Vortec engines and I doubt both would be bad.

A grill cover is as close as your nearest cardboard box that you don't need...that's what I use when I've wanted to restrict cooling. Just don't forget it when it starts to warm up, and don't cut it too short or you won't be able to easily get it out from between your radiator and core support or whatever.

I have a cheapo IR gun that's fairly inaccurate, I'll have to pick up a better one and then test it out again.

Might just go the cardboard route as well for now.

 

[df2x4]

Just a thought, is your truck equipped with a radiator that has the transmission cooler (warmer) built in? If so, is it still hooked up?

 

[Craig]

Just a thought, is your truck equipped with a radiator that has the transmission cooler (warmer) built in? If so, is it still hooked up?

Forgot to mention that, the truck does have a transmission and oil cooler.

 

[someotherguy]

Somewhere as cold as where you're at and I would be covering up the grille, too.

Be sure the fan clutch isn't stuck engaged.

As far as the cold air coming into the cab, your fresh air/recirculate actuator may not be working, or the HVAC box itself may not be sealing well against the firewall. Maybe in the past someone replaced the heater core and screwed up the foam rubber seal where the hoses come through, etc.

Richard

 

[454cid]

... Maybe in the past someone replaced the heater core and screwed up the foam rubber seal where the hoses come through, etc.

Richard

That could very well be the problem. My foam is bad there, and I don't know why. I've been the one to change the heater core. I use duct seal from Lowes on the outside of the firewall to seal it up.... if you're not familiar with it, it's a gray clay crap sold in the electrical department.

 

[L31MaxExpress]

I have a 1994 GMC Yukon. Engine is a L31R crate (based on 96+ vortec) that is stock aside from aluminum intake and headers. I live in Canada where it's normal to get -30 c / -22 f.

I'm having a hard time getting it up to operating temperature in the winter. It seems to want to stay around 140-160 degrees. I went on the highway for a couple of hours and the engine was unable to warm the transmission properly so the torque convertor wasn't kicking in. I ended up getting 10.5 mpg on the highway at 2600rpm. I do have 3:73 gears in the rear, but in the summer, it will kick down to about 2100-2200rpm and give me 14-16mpg on the highway. Everything in the cooling system is new and stock with the exception of a ac delco high flow water pump. I hate to run it that cold due to the premature wear that occurs. I know these old vortec based engines like to run in the 190-210 range.

I replaced the thermostat with a expensive oem one today rated at 195 but it seems to have not done much. Is there anything else I can do to help get the temperature up? I'm thinking of buying a grille cover, not sure where a good place is to get one for a 1994. Any suggestions appreciated.

Secondly, on the highway, I noticed a fair amount of cold air coming in from the passenger side when it was on defrost. It stopped when I put it on recirculate. It almost felt like there was cold air coming from inside the glove box when I opened it up. Otherwise everything is working fine. Could it be a faulty blend door?

Any suggestions with these quirks would be much appreciated. Thanks guys!

Weird, mine runs 178°F year round and likes running cool. Run them much over 190°F and the PCM pulls timing to keep it from spark knocking. Even then they often still spark knock on 87 with the factory timing maps.

 

[Craig]

Somewhere as cold as where you're at and I would be covering up the grille, too.

Be sure the fan clutch isn't stuck engaged.

As far as the cold air coming into the cab, your fresh air/recirculate actuator may not be working, or the HVAC box itself may not be sealing well against the firewall. Maybe in the past someone replaced the heater core and screwed up the foam rubber seal where the hoses come through, etc.

Richard

The heater core was replaced 2 1/2 years ago.

I don't think it's the seal on the firewall as the cold air completely stops coming in when I put the heat on recirculate. The second I take it off recirculate, it begins pushing in cold air again.

 

[wheelman]

In the old days.there was vehicles that had that problem.so they would come with a hose reducer.heater hose.would have a piece of pipe just a short piece that would stay set in the hose and slow down the flow.i bet some people complain Ed about not enough heat.