Overheating diagnosis help

[I_bRAD]

My dummy dash gauge informed me that my truck was overheating, looking for some help diagnosing the issue as I can't see anything obvious:

Fan clutch isn't great. When I stop the engine (hot or cold) the fan continues to spin for a moment. Additionally, if I rev it when it is cold the fan blades actually flex enough to hit the belt pulleys at around 4k rpm. It does seem to move air though. There doesn't appear to be any damage to the fan blades (missing pieces, cracks etc)
I am under the impression that the fan shouldn't do much at highway (80kms/hr) speeds though?

I am seeing overheating across the board, but particularly when idling I see a bigger spike. The fan clutch explains the idle I think, but still, at operating temp I am seeing ECT from the OBD @105C. When idling it went up to 123 before I intervened. It drops a couple degrees if I turn on the heat full blast but not down to the 85 or so I was expecting.

Here are some numbers at idle after it warms up:

ECT: 118C (244F)
Upper rad hose: 77C (170.6F)
Lower rad hose: 43C (109.4F)
cam cover (Front L): 92C (197.6F)
cam cover (rear R) 99C (210.2F)

I suspect the lower numbers at the hose is due to the poor heat transfer of rubber, and the cam cover measurements lead me to believe I'm in the ballpark of correct operating temp, but it's still reading pretty high as far as the truck computer is concerned.

Am I overthinking this? Will a new fan clutch solve my problem or should I continue to look for trouble? I'm in an area where I'm ordering online so each attempt at parts brings shipping charges and a wait so I'd like to get this right on the first attempt.

Do coolant temp sensors simply fail, or can they start to degrade over time? Is that something I can test with a resistance reading in hot water?

This is a 97 with the 5VZFE and it has about 390k kms.

No codes or check engine lights. Seems to run fine. If I hadn't noticed the gauge I'd never know any different.

Any help or advice appreciated! Thanks.

 

[jgue467]

When starting, especially in mornings, is there a roar from fan that quiets down after a minute?

Done the fan clutch test? roll up a newspaper, with engine running and very carefully insert into blades. A good clutch won't let you stop the blades. Some mechanics just hold blades while another starts, if able to hold then clutch is shot.

Replaced radiator cap? Those go south and won't hold pressure allowing temps to rise dramatically.

I don't really understand the temps you cite but as an example, mine in austin summers hovering above 100 for 8 hours a day, it can idle for hours, 195, tow in stop/go traffic, still 195. Runners have a very strong engine cooling system, yours should too.

 

[spartacus]

How old is the radiator and when was the last coolant service done?

 

[T4topher]

All the above mentioned plus I’d replace the thermostat while your at it and make sure it’s in the correct position. I can never remember if it’s the 12 o clock or 6 o clock position it needs to be in, I’m sure someone knows.. Might be worth doing a timing belt/water pump too..

 

[FordF150]

You keep overheating and you can throw that engine away.

I have a 2005 with 150,000miles and it has never had even one overheat.

Find out what it is right away.

radiator cap
thermostat stuck (not likely)
weak or bad fan going
radiator needs replacing (just got old)
leak
wp


take it to a pro shop for diagnosis

those HAND HELD thermoguns are not the best for accurate temperature readings.

 

[I_bRAD]

When starting, especially in mornings, is there a roar from fan that quiets down after a minute?

Done the fan clutch test? roll up a newspaper, with engine running and very carefully insert into blades. A good clutch won't let you stop the blades. Some mechanics just hold blades while another starts, if able to hold then clutch is shot.

Replaced radiator cap? Those go south and won't hold pressure allowing temps to rise dramatically.

I don't really understand the temps you cite but as an example, mine in austin summers hovering above 100 for 8 hours a day, it can idle for hours, 195, tow in stop/go traffic, still 195. Runners have a very strong engine cooling system, yours should too.

Haven't tried to stick anything in the fan, but it does seem to 'roar' like you said at start. I am concerned that something is allowing enough flex for the fan to hit the engine though, especially since I'd expect the fan to flex away from the engine, and not towards it. Can't feel any play in the water pump bearing.

 

[I_bRAD]

How old is the radiator and when was the last coolant service done?

coming up on 9 years and the cap was replaced at that time too. I will bashfully admit that was likely the last time the coolant was changed too! I only drive it 5000kms a year though so it doesn't get a lot of miles.

 

[I_bRAD]

weak or bad fan going

leak
wp

Do you agree a weak fan would only affect idle temps though?

I will have to look more carefully for a leak. I keep it in my wood shed so any leaks wouldn't be obvious on the ground...

 

[HiLife]

A 9yo radiator is most certainly has brown plastic because of age. Keep on a look out for micro cracks. Those cracks is the start of your radiator exploding from the 14 psi pressure, leaving you stranded.

Ya, it's all on the fan that keeps the engine cool below a curtain mph. As the mph picks up, ram air through the radiator takes over cooling it.
I know your over heating while idle.
Is it still over heating at 50+mph? What's the temp?

Personally I would do the radiator, cap, coolant and thermostat just as part of maintenance.

 

[I_bRAD]

A 9yo radiator is most certainly has brown plastic because of age. Keep on a look out for micro cracks. Those cracks is the start of your radiator exploding from the 14 psi pressure, leaving you stranded.

Ya, it's all on the fan that keeps the engine cool below a curtain mph. As the mph picks up, ram air through the radiator takes over cooling it.
I know your over heating while idle.
Is it still over heating at 50+mph? What's the temp?

Personally I would do the radiator, cap, coolant and thermostat just as part of maintenance.

Still overheating at speed, although not as bad. Took it for a spin last night and I was seeing ~220F Could get it down to 215 if I turned on the heaters.

That was at 50mph, which is about the top speed this thing ever sees.

 

[Wedgy]

Anything over 5 years on a radiator is asking for trouble, don't be cheap, just replace it and most likely it will solve your problems. That is if you haven't already fried your HG. Change the thermostat also and make sure the jiggle valve is in the 6 o'clock position.

 

[jgue467]

Just looked at mine, with original blade, all blades are 1.1 inches away from nearest bolts on pulleys.

I can't imagine how blades could flex so much, even started it, same location, revved up to 3K, same place.

I think that is a problem on yours. Maybe not The problem, but it is one far from normal.

Also, have you cleaned up between a/c condensor and radiator? When I offroad around tallish grass even with skidplates on, grass gets up between the two. Eventually it covers the lower half between the two on mine. Doesn't cause an overheating issue but it might on yours with the fan flexing.

I'd suggest replacing fan and clutch, plus radiator cap. Luck.

 

[spartacus]

Fan blades flexing and hitting is bad. Definitely need to fix that first before diving deeper into diagnostics.

 

[HiLife]

The plastic stock fan isn't sposed to be flexing bad enough to hit the engine. The fan clutch would slip before spining the fan fast enough. Fan clutch slip would lessening the drag on the engine for better gas mileage too.

I was at 192 after a heat soak today. I drove at 30 mph (I think second gear), held the very lit throttle with 2000 rpm and 22% engine load. After about 1/4 of a mile of driving like that the cooling system went down to 188.

Does your engine stay up there when doing the same drive sequence?

 

[I_bRAD]

Solved. The gauge isn't the dummy! The prolem was behind the steering wheel.

Not sure what's up with the fan, but I'm not going to fix it until something breaks. It only flexes that much when I hit >4000 rpm which pretty much never happens during use.

The problem was low coolant. I didn't see any leaks, and I've never had any obvious leaks but somewhere along the line I lost coolant. If it is leaking out over 5 years I can live with that. I did leave it in the garage tonight so I can see if there are any drips on the floor. Hopefully the cat doesn't come to visit!

Just drove to town and back (about 40 mins) and it held steady at 178-180. Can't do better than that.

Thanks for all the help and sorry to waste everyone's time! :high5:

 

[T4topher]

Not sure what's up with the fan, but I'm not going to fix it until something breaks. It only flexes that much when I hit >4000 rpm which pretty much never happens during use.

The problem was low coolant. I didn't see any leaks, and I've never had any obvious leaks but somewhere along the line I lost coolant. If it is leaking out over 5 years I can live with that. I did leave it in the garage tonight so I can see if there are any drips on the floor. Hopefully the cat doesn't come to visit!

Just drove to town and back (about 40 mins) and it held steady at 178-180. Can't do better than that.

Thanks for all the help and sorry to waste everyone's time! :high5:

If it happens when you hit 4K rpms that sounds like the fan clutch is toast. Could be part of the reason the fan is flexing so crazy. Basically the fan clutch isn’t engaging and it’s trying to spin the fan super hard.. Just a thought..

 

[JoeT4R]

Just want to ask, could/would a low coolant overflow reservoir have any impact on this? If yes, should I always have a full reservoir? Mine has been pretty low for at least 1 year and I have noticed slightly warmer temps during the summer months but nothing absurd or overly concerning. However if those can be eliminated by filling the overflow reservoir then of course I want to get on that NOW!

 

[I_bRAD]

If it happens when you hit 4K rpms that sounds like the fan clutch is toast. Could be part of the reason the fan is flexing so crazy. Basically the fan clutch isn’t engaging and it’s trying to spin the fan super hard.. Just a thought..

Sounds reasonable. I still can't figure out why the fan would flex towards the engine instead of away from it though as the reaction force should be opposite to the fan direction! Will keep an eye out for a used one perhaps; That's $100 I could use for something else at the moment...

 

[I_bRAD]

Just want to ask, could/would a low coolant overflow reservoir have any impact on this? If yes, should I always have a full reservoir? Mine has been pretty low for at least 1 year and I have noticed slightly warmer temps during the summer months but nothing absurd or overly concerning. However if those can be eliminated by filling the overflow reservoir then of course I want to get on that NOW!

Apparently the system can't suck all of the fluid out of the reservoir as I still had a bit in the bottom so wasn't too concerned, but when I actually opened up the rad and filled it I had to add quite a bit. For a few bucks worth of coolant I say do it!

 

[19963.4lsr5]

Just want to ask, could/would a low coolant overflow reservoir have any impact on this? If yes, should I always have a full reservoir? Mine has been pretty low for at least 1 year and I have noticed slightly warmer temps during the summer months but nothing absurd or overly concerning. However if those can be eliminated by filling the overflow reservoir then of course I want to get on that NOW!

At every fillup I check the oil level and shake the fender to make sure my tank is between the low and high Mark. Cold engine I have it on the top line so when the engine gets up to temp I’m above the top line around 1/2”. Which it how it’s supposed to happen. That’s how all the air gets purged out of the cooling system.

Never let it go below the low mark.


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