Intermittent Overheat
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Cross-Country
Joined: Aug 2011
Posts: 82
Likes: 4
Good idea, this would show it the tstat or pump isnt working?
FTE Legend
Joined: Nov 2015
Posts: 30,983
Likes: 4,136
From: Angier, NC
You did not say how long you are sitting not moving? if you have the AC on or not and how high the gauge gets from normal and where normal is on the gauge.
Being you can raise the RPM and the temp comes down and it dose not go up when driving / moving it is a air flow thing or lack of air flow.
How far does the fan sit from the edge of the shroud and how far in?
Fan blades should be half in the opening. If too far air will hit the shroud and get pushed back and block any air flow.
If out too far out it will not pull air thru the radiator and shroud but from the engine bay.
How clean is the coils / fins of the radiator & AC condenser?
Dead bugs and leaves can stop air flow.
As a air flow test get a sheet of paper and with the motor at idle see if the paper will stick to the grille.
If not low or no air flow.
Dave ----
Being you can raise the RPM and the temp comes down and it dose not go up when driving / moving it is a air flow thing or lack of air flow.
How far does the fan sit from the edge of the shroud and how far in?
Fan blades should be half in the opening. If too far air will hit the shroud and get pushed back and block any air flow.
If out too far out it will not pull air thru the radiator and shroud but from the engine bay.
How clean is the coils / fins of the radiator & AC condenser?
Dead bugs and leaves can stop air flow.
As a air flow test get a sheet of paper and with the motor at idle see if the paper will stick to the grille.
If not low or no air flow.
Dave ----
Thread Starter
|
Cross-Country
Joined: Aug 2011
Posts: 82
Likes: 4
You did not say how long you are sitting not moving? if you have the AC on or not and how high the gauge gets from normal and where normal is on the gauge.
Being you can raise the RPM and the temp comes down and it dose not go up when driving / moving it is a air flow thing or lack of air flow.
How far does the fan sit from the edge of the shroud and how far in?
Fan blades should be half in the opening. If too far air will hit the shroud and get pushed back and block any air flow.
If out too far out it will not pull air thru the radiator and shroud but from the engine bay.
How clean is the coils / fins of the radiator & AC condenser?
Dead bugs and leaves can stop air flow.
As a air flow test get a sheet of paper and with the motor at idle see if the paper will stick to the grille.
If not low or no air flow.
Dave ----
Being you can raise the RPM and the temp comes down and it dose not go up when driving / moving it is a air flow thing or lack of air flow.
How far does the fan sit from the edge of the shroud and how far in?
Fan blades should be half in the opening. If too far air will hit the shroud and get pushed back and block any air flow.
If out too far out it will not pull air thru the radiator and shroud but from the engine bay.
How clean is the coils / fins of the radiator & AC condenser?
Dead bugs and leaves can stop air flow.
As a air flow test get a sheet of paper and with the motor at idle see if the paper will stick to the grille.
If not low or no air flow.
Dave ----
guage sits right at or slightly above dead center and moves all the way to the right when it overheats
Hotshot
Joined: Feb 2004
Posts: 10,866
Likes: 2,626
From: The Shenandoah Valley
Originally Posted by frdbronco8
Thread Starter
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Cross-Country
Joined: Aug 2011
Posts: 82
Likes: 4
Looking for clues, I saw where you stated that you removed AC a few posts ago, but I wonder if you have tight belts running the water pump consistently. I see the bracket adjusting the alternator tension is a welded deal, is it a sound weld still, keeping the belt tight. I also see the PS pump is adjusted to maximum and looks like a bolt missed the head, is that also a tight belt? One or maybe both belts also turn the water pump.
FTE Legend
Joined: Nov 2015
Posts: 30,983
Likes: 4,136
From: Angier, NC
New lower hoses do not come with springs, you have to reuse the old one.
If there is no spring in the lower hose as the motor RPM goes up the hose gets sucked closed and stops the flow.
Dave ----
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Lead Driver
Joined: Nov 2000
Posts: 6,651
Likes: 352
From: Albuquerque
Could still be the fan clutch. Any goo around the clutch part? they will turn faster with rpm just more so when hot. also make sure no loseness of the blade if you move it front to back. It should feel tighter when hot if you spin it by hand.
Thread Starter
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Cross-Country
Joined: Aug 2011
Posts: 82
Likes: 4
Not fan clutch
Replaced the fan clutch with no change. This time I noticed when it overheated the lower radiator hose felt cool and the upper was very hot.... would that be thermostat? Maybe ingot a bad one.
Cargo Master
Joined: Mar 2008
Posts: 2,589
Likes: 212
From: Washington
Just take out the thermostat. See how it does with out it.
Logistics Pro
Joined: Jul 2005
Posts: 4,217
Likes: 154
It could be a stuck-closed thermostat - but if you don't know how old your radiator is, it could be a clogged radiator, inside the fins. An engine which heats up at speed is a sign of a bad radiator, but yours looks fresh, and has also heated up at idle. Maybe a previous owner dumped a bunch of Stop-Leak in it?
You could try removing the thermostat and running/driving it, and see what it does. One thing to remember though is that in some cases, running without a thermostat will cause an overheat, as the coolant is being moved too quickly to cool the engine and get cooled in the radiator.
And definitely check to make sure that your lower radiator isn't collapsing. You can squeeze it and feel for the spring inside. At RPM, the lower hose can suck closed, and impede coolant flow.
When I did my cab swap and removed the whole doghouse and radiator I found the spring in the upper hose... So I switched it. They also had the seatbelt retractors on the wrong side!
You could try removing the thermostat and running/driving it, and see what it does. One thing to remember though is that in some cases, running without a thermostat will cause an overheat, as the coolant is being moved too quickly to cool the engine and get cooled in the radiator.
And definitely check to make sure that your lower radiator isn't collapsing. You can squeeze it and feel for the spring inside. At RPM, the lower hose can suck closed, and impede coolant flow.
When I did my cab swap and removed the whole doghouse and radiator I found the spring in the upper hose... So I switched it. They also had the seatbelt retractors on the wrong side!
Fleet Mechanic
Joined: Mar 2013
Posts: 1,662
Likes: 1,063
From: Montana
If the upper hose is hot I think the thermostat is opening just fine, but if the lower hose is still cool the coolant isn't flowing through the radiator like it is supposed to. I am thinking there's some blockage in the radiator. Might be able to use some radiator flush from the parts store to get it flowing right again or it might need to be professionally cleaned (if you still have a radiator shop in your area).
Thread Starter
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Cross-Country
Joined: Aug 2011
Posts: 82
Likes: 4
I bled the system again and so far it's not overheating.... seems like everytime i bleed it works for a while and eventually starts doing it again. I didn't have an overflow tank, could I be losing enough coolant to cause this? It was just above the level of the fins when it did it last time. It's topped off now and I added an overflow so we will see what happens.
Logistics Pro
Joined: Jul 2005
Posts: 4,217
Likes: 154
If you are going to run an overflow tank, then you need to switch to a "recovery" style radiator cap which will allow coolant to be sucked back into the radiator upon cool-down.
A non-recovery cap is basically a check valve, and won't let coolant back in.
A non-recovery cap is basically a check valve, and won't let coolant back in.