91 3.0 overheating... I thought I fixed it. Advice from the Gurus please....

[dvdswan]

Quick story, I bought the truck with a new water pump installed already. Vehicle got hot on me (very end of the normal range) in traffic, as soon as traffic started moving temp gage went down below 1/2 gage. I checked the fan clutch which was bad, it would spin freely easily when hot or cold. Well, I could not break the fan clutch loose, even tried heat. So rather than friggen messing with it all weekend, I cut off the fan clutch and installed a new water pump. I made sure to coat the long studs with gasket sealer good as possible leak spots. The system doesn't leak and bled just fine. Also, replace both rad hoses and both heater hoses.

I've been searching on here and read that its possible with the 3.0 when it gets hot that the head gaskets collapse. Is this really a thing? I mean heads are torqued down to (swag) 110 ft. lbs. or something, how can it collapse. Maybe its the wrong word.

Anyway, So yesterday I'm doing my normal running between job sites, and pull into a parking spot, temp was high a little higher than 3/4 gage (not hot by my opinion) and still in the normal range. I heard water boiling in overflow reservoir. I heard the fan clutch driving, highway speeds gage was below 1/2, street driving is where the temp rose.

Is it possible that the one of the head gaskets blew? There's no water in the oil (thankfully) and idling for 20 minutes it doesn't go past 1/2 gage. I'm stumped.

 

[franklin2]

Around town overheating is a airflow problem. Do you have a fan shroud on it? Fan should be very noisy when it's locked up. And I would not trust the factory gauges for troubleshooting purposes. You can buy a cheap infrared thermometer gun from Harbor freight to see if the gauge is lying to you.

12:1 Infrared Laser Thermometer

Amazing deals on this 12:1 Infrared Laser Thermometer at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

 

[dvdswan]

Has fan shroud, new fan clutch and it does engage as it should. Not really going of the gage, yes it gets high, it has not been out of the "normal" range, it did boil over in the overflow tank.

If its possible its more of a load on the engine I think. I had it idling for 20 minutes + and the temp rose, fan engaged and temp dropped. No boiling.

 

[franklin2]

The boiling into the tank could be a faulty radiator cap. Take it off and see if the thin brass piece has any cracks in it. Replacing the cap is not going to change the temp reading, but should stop the boiling over.

 

[Dirtman]

What that guy said.

 

[RonD]

First off, water/coolant does not boil in the overflow tank, bubbles in the overflow tank means there is air in the top of radiator and its being pushed out into the overflow tank and bubbling up

210deg is 1/2 on Ford Temp gauge, 3/4 is about 260deg, and IS overheated, time to pull over

Head gaskets are Crushed by the engine overheating
Metal expands when heated, that's why heating up a part can break it loose, the metal expands and breaks free of rust or ??
Since the heads are torqued down, when engine is allowed to overheat the head metal can only expand down toward the block............................and that can/will Crush the head gasket's metal rings that seal the cylinders
Cylinders are surrounded by coolant passages, so if the metal ring "breaks" then the 900psi pressure inside a firing cylinder will find its way to a coolant passage via the softer material of the head gasket, and that injects "air" into the cooling system, AND displaces coolant in the head causing overheating to start
As this "air" is circulated with coolant it will find its way to the highest points, heater core and radiator
Heater will often get cold as this "air" blocks flow thru heater core, and overflow tank will start to bubble as the "air" is pushed out

You can smell the overflow tank and radiator for "exhaust" smell, after engine has cooled down
The "air" is actually "exhaust" gases from cylinder firing, its just exiting the cylinder thru cooling system instead of exhaust manifold

You can do the "Glove Test" to see if head gasket is the issue, but it reads like it may be
Or leave rad cap off, top up rad and start COLD engine, coolant should NOT start to over flow, may be one burp but that's it, let it idle
If coolant is overflowing then you do have a crushed head gasket, the "air" coming in is displacing the coolant in the head causing radiator to overflow, and you will start to see bubbles in radiator

3.0l Vulcan engine is not known for failing head gaskets, like the 4.0l but any engine run at 260deg for very long will get a Crushed head gasket, it just physics

 

[dvdswan]

Thank you for the detailed explanation @RonD, I guess I was overthinking the "crushed gasket".

I'll do the glove test just for piece of mind but pick up a rad cap. I appreciate everyone's input. Thank you.

I know the rad cap is aftermarket but is there a better one to go with like gates or something.

 

[Dirtman]

Ron sure does love the glove test!

 

[dvdswan]

Ron sure does love the glove test!

If its piece of mind who's complaining.

 

[RonD]

Yes, I am cheap
I like "free" tests, get physics working FOR ME instead of always against me, lol
Entropy SUCKS

 

[Dirtman]

Yea! Screw physics! Let's all go beat up Rudolf Clausius!

 

[RonD]

Lets not "shoot the messenger"

 

[Eddo Rogue]

You would know if the head gasket is bad, by which I mean you would see tremendous amounts of smoke and steam billowing out of your exhaust pipe, especially during acceleration.