'91 4.0L getting hot at low RPMS?

[high5]

my '91 ranger 4x4 with 4.0L and auto is used on my inlaws farm for my hunting truck. i use it year round and it is getting warm when just idling around or when parked. i have swapped the fan clutch which did not correct the issue and neither did a new thermostat. in cooler temps i don't have the problem but now that it is up around 100degrees i have started having the issue. if when parked i rev the motor up to around 2500 RPM it will cool back down. also if i speed up, which increases the RPM and air flow through the radiator it also cools down. you can also gather from this that if i run down the road i have no issues there either. just at slow speeds when putting around the farm. any ideas?

 

[nine-teen91stxranger]

maybe a faulty waterpump or the rads clogged, dont do it yourself, you cant get it 100% clean, bring it in.

 

[cr_the_machinist]

Have you replaced the radiator cap in the past? May be worth trying since it's a part under $10 and take 5 seconds to change. If the system in not under enough pressure, it prone to boiling over and overheating.

 

[289-tiger-]

Good advice on the pump and radiator above, also do not overlook the possibility of an old serpentine belt slipping on the pump pulley.

Good luck

 

[high5]

thanks for all of the replies. i'll check all of these things.

 

[Hellcat]

my '91 ranger 4x4 with 4.0L and auto is used on my inlaws farm for my hunting truck. i use it year round and it is getting warm when just idling around or when parked. i have swapped the fan clutch which did not correct the issue and neither did a new thermostat. in cooler temps i don't have the problem but now that it is up around 100degrees i have started having the issue. if when parked i rev the motor up to around 2500 RPM it will cool back down. also if i speed up, which increases the RPM and air flow through the radiator it also cools down. you can also gather from this that if i run down the road i have no issues there either. just at slow speeds when putting around the farm. any ideas?

You might want to get your radiator flow tested. I had a similar problem and finally got the radiator tested I only had about 40% flow. I know this sounds simple but I missed it because I could see the antifreeze moving when I took the cap off. I had flushed it and it looked like the antifreeze was moving around good. A new radiator and the problem was solved. As touchy as the 4.0 heads and head gaskets are about over heating I would not take many chances.

 

[high5]

Update:
After hunting season i brought the truck home to work on it. I replaced radiator and water pump. I had previously replaced thermostat, rad cap, fan, and fan clutch. All of this and i still have the same issue. If i increase the rpms off of idle the temps will come down. If i do not run the a/c it does not heat up near as bad. I am thinking it is an air flow issue at idle. Any ideas on a fan that will fit my application, that will help with air flow at idle? I would prefer mecanical over electric. Any help/ideas will be appreciated.

 

[alwaysFlOoReD]

Is the shroud still there? It's important!

Richard

 

[high5]

Is the shroud still there? It's important!

Richard

yes it is there and in good shape.