Weird overheat scenario....

[rwbenner]

To all, hello again.....I'm back at the well asking for more help/advice from everyone. Grab a cup of coffee though, a lot of "back story" to this one....

I have a 2002 Sport Trac with north of 300,000 miles. I let my son borrow it while he was visiting from Cali the other week, and he called me with an overheat problem (temp gauge on "high", steam from under hood while engine was idling in a parking lot after about 5-7 minutes). My brother was closer to him than I was (he also does mechanical work), and he stopped by to help out. He could not find any leaks from any hose or the weep hole on the bottom of the water pump, and he only added about half a gallon of antifreeze to the radiator to top it off). I then told my son to drive it straight back to me, watch the temp gauge, and call me if it got near the "H" on the temp gauge. On his way home, he stopped at TB for some drive through food (albeit I told him to drive straight back), and while waiting for the food he said the temp gauge started creeping up again, but never got to "H". Once he started driving on the road, the temp gauge went back down and there were no more overheat concerns.

When he got the truck to me, I waited for it to cool and checked the radiator, the level was down a wee bit, but I could not see the radiator core yet so I figure that was good. The reservoir was empty. My initial thought was that the fan clutch had gone bad and was not engaging the fan enough to allow adequate cooling during idle. I did notice however once he got it back to me (and this is where I need your help), that the fan blades had been striking the upper part of the radiator shroud to the point that it wore through part of the shroud, and the fan blades all have impact grooves wore into them from repeatedly striking the upper shroud. WHAT IS UP WITH THAT? While I realize that impacting the shroud will slow the fan speed at an idle and contribute to overheating, I have no reasonable explanation why they are rubbing. There is no play in the fan blade indicative of bad bearings in the pump (and beside I think the serpentine belt runs over top the fan blade pully - forcing it downwards if anything), and the pump is not leaking. Finally, the radiator and the shroud retaining bolts are all intact, nothing has moved or shifted.

I ordered another fan clutch, and was going to swap out the thermostat housing for the metal one while there (BTW, does the thermostat have a seal I need to buy?) But the shroud-fan blade dilemma has me perplexed.

So to wrap things up, here are my specific questions
1) Does it sound reasonable that the fan clutch could be faulty?
2) Any idea what may cause the fan blades to suddenly start to rub on the upper radiator shrouding (at the 12 o'clock position of the shroud)?
3) Does the thermostat have a seal or gasket that I need to buy separately from the thermostat?

Thanks to all for your advice in helping me keep this '02 ST with 300k on the road for just a few more miles

Randy

 

[dvdswan]

1) Does it sound reasonable that the fan clutch could be faulty?
2) Any idea what may cause the fan blades to suddenly start to rub on the upper radiator shrouding (at the 12 o'clock position of the shroud)?
3) Does the thermostat have a seal or gasket that I need to buy separately from the thermostat?

Randy

1) Yes, at 300k a fan clutch can be faulty.
To test, with the engine cold, spin the fan. There should be some resistance but it will turn and spin 1 to 3 times around. If it spins freely or does not spin at all you have a bad fan clutch. If it is locked up, it's not all bad you will still have cooling just the typical loud roar of the fan when the clutch is engaged. On cold morning you should hear this for about 30 seconds to a minute before the clutch gets to ambient temp or even operating temp.

2) Several thoughts on this. How are your body mounts, specifically, the front 4 (2 on the rad support to frame and 2 on the front of the cab) could be bad/worn out or rusted. Radiator supports (the seats where the radiator sits) could be bad/worn out or rusted. I would also check your engine mounts. Yes, normally when these are bad the lower shroud would be chewed up. But on the chance that both are bad and the engine had shifted position this would happen as well.

3) My T-stat housing came with a new t-stat, gasket, and seal. You just need to read the fine print explaining what you are buying.

 

[rwbenner]

Thanks for the intel….In was thinking maybe transmission mount was failing and allowing the front of the engine to pitch up, but I didn’t think about the radiator or cab mounts….those are good ideas! Many thanks!

 

[dvdswan]

A trans mount will generally give a thump on takeoffs from shifting positions.

 

[rwbenner]

@dvdswan, u nailed it. I thought I had looked thoroughly at both radiator mounts/bolts but after getting the fan and shroud off and out of the way, I saw this (see pic) just rattling on the frame. Not attached anywhere….just trapped by the radiator and engine bay components so it never fell onto the road. lol.

Anyway, I effected repair on that, got the Tstat housing swapped, and the new fan clutch in the fan housing. Tomorrow is reattaching the fan and shroud and topping off the antifreeze.

I was wondering about the oil though, I seem to remember that one should always change oil with an engine overheat….but the oil does not look or smell burned/cooked.