Engine gets close to overheat with ac on

[Bunger317]

Got a problem that's driving me nuts. Got a 1994 4.0 w/a4ld. Runs great. Gets shit mileage but I'm on 33s with 3.73s. Anyways I'm in so cal and it's been hot. 100-105° ambient. Since it got hot whenever I run my ac the water temp starts climbing. Gets up towards the A or L in normal. I shut the ac off and it starts cooling back down after a few minutes. So far I've replaced water pump. Thermostat(tried a 197 and 180). new radiator. Fan clutch seems to work fine. When it gets hot I can hear the fan roaring when I leave a stop sign. Flushed out the heater core with the hose. Ran a combustion gas test on the radiator to rule out head gasket. I've got a 180 stat in it now and it runs down toward the N until I turn the ac on and sit at a light then it starts climbing. With the 197 stat with my infared thermometer I was seeing as hot as 225 on the t stat housing and 205-210 on the upper radiator hose. When it gets real hot I've only got about a 5-10° difference between the upper and lower radiator hose. Any ideas? It's too damn hot to not be able to run my ac.
Once the temp gets up it doesn't cool down even doin 55 on the highway. It won't cool back down till I shut the ac off.

 

[rusty ol ranger]

205-210 doesnt seem to bad under those conditions.

Do any of your other gauges act wonky?

 

[Bunger317]

205-210 doesnt seem to bad under those conditions.

Do any of your other gauges act wonky?

Negative. And my water temp gauge seems to work correctly. With the 180 stat it stays below N. With the 192/197 it stays around the R.

Ive just never had a vehicle where the water temp fluctuated this much.

Is the infared gun at the upper radiator hose and accurate way to judge how hot it's actually getting?

 

[rusty ol ranger]

Negative. And my water temp gauge seems to work correctly. With the 180 stat it stays below N. With the 192/197 it stays around the R.

Ive just never had a vehicle where the water temp fluctuated this much.

Is the infared gun at the upper radiator hose and accurate way to judge how hot it's actually getting?

I would think so. Its the last stop before the radiator.

My 97 F250 HD moves around alot too. Its got a 180* stat and if im just cruisin itll sit right around "n" but if im makin that 460 gimmie what shes got ive seen up to midway on the gauge before.

With the AC on and those tires youre workin that motor pretty hard...and thatll make heat.

This might be a good @RonD issue.

 

[Bunger317]

I would think so. Its the last stop before the radiator.

My 97 F250 HD moves around alot too. Its got a 180* stat and if im just cruisin itll sit right around "n" but if im makin that 460 gimmie what shes got ive seen up to midway on the gauge before.

With the AC on and those tires youre workin that motor pretty hard...and thatll make heat.

This might be a good @RonD issue.

I agree. It's especially heats up if I drive on the highway for a while with the ac on them come to a stop light. If I start the ac as soon as I get in the truck and don't stop it stays relatively cool. It's after I've been going awhile and come to a stop that it builds up heat

 

[rusty ol ranger]

I agree. It's especially heats up if I drive on the highway for a while with the ac on them come to a stop light. If I start the ac as soon as I get in the truck and don't stop it stays relatively cool. It's after I've been going awhile and come to a stop that it builds up heat

And youre sure the fan clutch is working right?

It could *possibly" be worn impeller blades on the pump. But nevermind you changed that.

Unless the radiator is plugged?

 

[Bunger317]

And youre sure the fan clutch is working right?

It could *possibly" be worn impeller blades on the pump. But nevermind you changed that.

Unless the radiator is plugged?

itseems to love a ton of air idling and when I leave a light when it's engaged it roars like a diesel truck fan so I'm assuming it's working right.

new water pump and new radiator

 

[RonD]

Fan Clutch maybe?

The fan is only there to pull air thru radiator when driving under 30mph, above that and the speed of vehicle forces more air thru radiator and inside engine bay than any fan can
This is why there is a fan "clutch", its mostly disengaged when you need the horse power, at speed, then re-engages when you don't need the power, driving slow or stopped

Pretty simple device, it has a bi-metal spring on the front next to center of radiator, the radiator heats up the spring and it expands, which closes valve(s) inside the clutch which causes the fan blade to spin faster, closer to water pump shaft RPMs, i.e. grabs more air to cool radiator more
As radiator cools down, at speed, fan blade becomes free spinning, no HP draw

Easy to test
Cold engine, sat over night, open hood and spin the fan, should move but not spin, its "cold locked/engaged"
Start engine
Should hear a "roar" from the fan grabbing air, its locked, then it quiets down after 5 seconds or so, unlocked
Shut off engine
Spin fan blade again, should be easy to spin, now unlocked

If it spins easy before starting then most likely its bad, but one more test, after driving and getting home, i.e. engine/rad all warmed up, shut off engine and open hood
Spin the fan, should be locked, it will move but not spin
If it spins then replace fan clutch

Test fan clutch first its free and easy

Next is radiator, also free to test
After engine/rad is warmed up, i.e. when you get home
Remove the two bolts that hold the fan shroud to radiator and move it back out of the way
Run you hand over the radiator fins
It should be even heat but warmer the closer your hand gets to upper rad hose and cooler towards lower rad hose
If you feel any cold spots that will be blocked radiator tubes, you will feel it, pretty noticeable

If fan clutch tests as OK, and radiator feels OK then replace water pump

 

[Bunger317]

Fan Clutch maybe?

The fan is only there to pull air thru radiator when driving under 30mph, above that and the speed of vehicle forces more air thru radiator and inside engine bay than any fan can
This is why there is a fan "clutch", its mostly disengaged when you need the horse power, at speed, then re-engages when you don't need the power, driving slow or stopped

Pretty simple device, it has a bi-metal spring on the front next to center of radiator, the radiator heats up the spring and it expands, which closes valve(s) inside the clutch which causes the fan blade to spin faster, closer to water pump shaft RPMs, i.e. grabs more air to cool radiator more
As radiator cools down, at speed, fan blade becomes free spinning, no HP draw

Easy to test
Cold engine, sat over night, open hood and spin the fan, should move but not spin, its "cold locked/engaged"
Start engine
Should hear a "roar" from the fan grabbing air, its locked, then it quiets down after 5 seconds or so, unlocked
Shut off engine
Spin fan blade again, should be easy to spin, now unlocked

If it spins easy before starting then most likely its bad, but one more test, after driving and getting home, i.e. engine/rad all warmed up, shut off engine and open hood
Spin the fan, should be locked, it will move but not spin
If it spins then replace fan clutch

Test fan clutch first its free and easy

Next is radiator, also free to test
After engine/rad is warmed up, i.e. when you get home
Remove the two bolts that hold the fan shroud to radiator and move it back out of the way
Run you hand over the radiator fins
It should be even heat but warmer the closer your hand gets to upper rad hose and cooler towards lower rad hose
If you feel any cold spots that will be blocked radiator tubes, you will feel it, pretty noticeable

If fan clutch tests as OK, and radiator feels OK then replace water pump

thanks for the reply.

new radiator and water pump.

fan clutch has been tested and worked. Engaged when cold and hot. When it's extra warm it roars everytime i leave a stop light. Even after letting it warm up in my driveway in the morning it roars the first couple blocks when I leave. It seemed to be moving a ton of air at idle.

could there be an issue with the ac system that could be cause extra heat to buildup?

 

[rusty ol ranger]

Is your fan shroud intact?

A missing fan shroud lets the fan air kinda blow everywhere rather then pulling air thru the radiator

 

[rusty ol ranger]

thanks for the reply.

new radiator and water pump.

fan clutch has been tested and worked. Engaged when cold and hot. When it's extra warm it roars everytime i leave a stop light. Even after letting it warm up in my driveway in the morning it roars the first couple blocks when I leave. It seemed to be moving a ton of air at idle.

could there be an issue with the ac system that could be cause extra heat to buildup?

I doubt it

 

[Bunger317]

Is your fan shroud intact?

A missing fan shroud lets the fan air kinda blow everywhere rather then pulling air thru the radiator

fan shroud is in tact.

 

[rusty ol ranger]

fan shroud is in tact.

Im outta ideas on this one bud

 

[Bunger317]

Starting to wonder if this is just normal for an old truck like this?

wondering if it could be an issue with the motor? Egr or something causing it to lean out? Replaced 02 sensors awhile back after getting a 172 code. They thing runs incredible minus the 13 mpg and now this ac heat issue

 

[rusty ol ranger]

Starting to wonder if this is just normal for an old truck like this?

wondering if it could be an issue with the motor? Egr or something causing it to lean out? Replaced 02 sensors awhile back after getting a 172 code. They thing runs incredible minus the 13 mpg and now this ac heat issue

If it was lean i would think the symptoms would be there regardless of AC operation.

Plus there would be codes and the ECM will dump fuel To it to compensate.

I honestly think its just a combination of it being hot as hell outside and the engine getting worked