Engine overheating at idle - trying to diagnose

All,

First time poster, second guessing my choice to buy a used '95 B3000 that needs to make a trip x-country next week. I'll start by saying that I've been reading as much as I can on this topic, enough to be dangerous, but not enough to know what I'm actually talking about.

Here's the primary problem: my V6 3.0L B3000 is overheating to dangerous levels while at idle, unless you rev the engine. Here are the symptoms:

1. Engine runs nice and cool at speeds above about 30 mph.
2. At idle or at slow speeds, coolant gauge quickly (<2 min) will peg out at the max.
3. While at idle, if you put truck in neutral and rev to around 3K, coolant temp gauge will quickly drop back down to middle or below
4. Heat just won't come on if you start up and drive while it's cold out, even for 30 minutes at 40 MPH. But if you let it idle for a while, it will kick in nice and warm.

Here are some additional things that may be related:

1. Transmission fluid seems GROSSLY overfilled. As in, 3 times higher than the high fill mark. I tested this while hot and idling, following proper method. It doesn't seem foamy, but I don't know what it's supposed to look like otherwise.
2. Small puff of white smoke when I start up the truck most of the time
3. Coolant reservoir is full, almost to the neck, and the radiator seems not at all full. Almost as if it's not flowing back into the radiator. Have not yet tested this from a cold start until hot and bubbling, to see how much the fluid should expand, or how it flows in. This is just an observation while cold.
4. Previous owner supposedly replaced the thermostat. I'm not convinced they did this at all, or that they did it properly.
5. I can spin the fan with mild resistance after it's been freshly driven. It is not free spinning. It is also not stuck. And I jammed some newspaper in while running and wasn't able to stop the fan - it seems to be on there pretty good.
6. Engine definitely leaks oil, possibly some other fluids.
7. Pulled a spark plug and it was totally burnt out, possible oil on threads but could have been my PB blaster. Will check more tonight.
8. Engine oil seems fine, not milky, not overfilled.

I have not yet checked compression or done a coolant flush. Will do compression check tonight, but fluid seems bright blue and very clean. Radiator cap seems clean and new, wouldn't expect it to be that. Not sure what kind of job was done on the thermostat, but I'll be checking it when I do a coolant flush in a couple of days.

Here are my questions:

• Is there a chance this is the fan clutch? I don't know how loose it should be when cool, or how to test that it's fully engaging / disengaging.
• With all of these symptoms, some of which could be unrelated, could this just be air in the coolant system and it needs a proper bump?
• How likely is it that this is the water pump impeller going bad? There's no wobble in the bearings, at least.
• How likely is it that this is a blown head gasket? It sounds like this would mess up the vacuum line, force coolant out of the radiator and into the reservoir. But it doesn't explain why the system cools down so quickly when I rev the engine, which sounds more like a water pump issue.
• What else could this be? Bad vacuum lines? Clogged coolant line somewhere? Something else?
• What possible causes are there for why the coolant reservoir is so full and the radiator is so low?

I desperately need help, would like to eliminate the things this isn't and make sure the vehicle doesn't explode on me and destroy the engine during my 3,000 mile trip next week.

I'd suggest you go down the list you made. starting with the fan clutch.. It was fan clutch the on my truck. Had it changed and it's never overheated in traffic again!

.

Welcome to TRS

A lot of good info in your post

Yes, rising temp when stopped and dropping temp when driving, is usually Fan Clutch, or more specifically air flow thru the radiator.
The Fan and shroud's sole purpose is to keep air flowing thru the rad or no cooling takes place.
When driving there is air flow, when stopped there is not so fan is used to to keep air flow going.

But your other symptoms point at other issues as well.

I would do the Glove Test first, it is free
It tests for leak from cylinder to cooling system, i.e. blown head gasket or cracked head

Cold engine
Remove rad cap
Remove overflow hose from rad, plug opening with vacuum cap or ??
Coolant should be down about 1" from top of rad for test, down more than 1" is fine.
Disconnect Coil Pack wires, you want a no start

Put Latex glove over rad cap opening seal it with rubber band, or you can use a balloon or even a condom instead of the glove.
Cooling system is now sealed.

Crank starter motor and watch glove
If should just lay there no movement at all.

If it starts to bounce/inflate, then you have a cylinder leaking pressure into the cooling system, for sure.
Blown head gasket or cracked head.

You can remove 1 spark plug at a time and crank engine, when bouncing stops last spark plug removed was from leaking cylinder, put it back in and retest to confirm.


Reasons I would suspect cylinder leak are these:
Full over flow
No coolant return on cool down
Heat up at idle, cool down when RPMs increase, so not related vehicle speed/air flow.

A cooling system has no pressure when cold, pressure comes from coolant heating up and expanding, this doesn't happen until coolant is above 160degf.
As coolant expands pressure inside the system builds up to 14psi(rad cap rating), at 15psi rad cap's big spring is pushed open and coolant will flow into the overflow tank.

After shut down coolant cools down and shrinks, pressure in the radiator goes down and will get to -1psi, the small spring in rad cap is pulled open and coolant is sucked back into the radiator from overflow tank.

This type of system is self purging for air, air in the system will make its way to highest point, top of rad, when coolant heats up rad cap opens and the air is the first to be pushed out to overflow tank, it will bubble up in the overflow tank and be gone.
When system cools down again coolant will be sucked back in not air, so rad stays "topped up".

If a cylinder is pumping air and pressure into the system, the 14psi cap opens fairly quickly pushing cold coolant out and filling the overflow tank, you would also see some bubbling in the tank as the air makes it to the top of rad.
As engine heats up and coolant level drops you can get over heating.
At low RPMs the air slows coolant flow so you get hot spots , as RPMs increase air is pushed out of the way allowing coolant to flow and temp drops.

At shutdown coolant cools down but system stays under pressure so no coolant can be sucked back in from overflow tank.

I would do the glove test to either find out you have a gasket issue or take that off the table, so you can look at other possible things

Great write-up, RonD. I will try do the glove test tonight, maybe even before I attempt a compression test. I'm guessing I should also pull the fuel pump relay when I do this?

Really hoping that it's not the head gasket - that's more $$ than I'm in a position to cover.

Still trying to work out if the trans fluid massive overfill is related to this, or just a colossal oversight from the PO.

If I'm not getting any glove movement, is the next thing to do really to just pull the fan clutch? Or should I try to burp the system somehow? Would any of these symptoms be caused by the PO putting in the wrong thermostat, or installing it wrong?

Denisefwd93, good to know. I'm thinking of reshuffling my list from cheapest test through most expensive / hardest to prove:

1. Glove test
2. Burp system
3. Compression test
4. Manually move fluid from reservoir back into radiator and see what happens
5. Coolant flush and thermostat inspection / replacement
6. Fan clutch swap
7. Water pump swap

I'm worried that a fan clutch swap is just not enough to get this done, in case it isn't the problem. I'd hate to tear down that far and then get so close to the water pump, only to have to do it again later. Is there any other way to test the fan besides trying to spin it, to see if that clutch is going? Before you swapped your fan clutch, did you have the same problems, where the engine would overheat at a standstill unless you revved the engine? It seems like a fairly quick fix, but I'd rather not waste the money just guessing at different things.

I should probably have mentioned that I broke the purge valve solenoid after I got a P1443 error and pulled it to clean it out but broke it getting it back in. I have a replacement coming, and in the meantime there's an open vacuum line after the purge sensor, between it and the carbon canister. I just shoved a bolt in there because it was some weird plastic tube with rubber tubing around it and I couldn't crimp it, but I should put that back in order in a day or two. Would that small vacuum leak around my temporary fix have anything to do with any of this, or is that unrelated?

Why r u making it so complicated? There are very simple ways to check the fan clutch. Nothing major to teardown needed rent the special wrench and change it! "Ur welcome" Or màybe my posts are invisible lol

Sorry, not trying to make it complicated, just trying to avoid buying parts until I know exactly what I need. My local store only has the severe duty fan clutch, which is more pricey than the regular replacement (but less than an engine, I guess). Reading up on the fan clutch swap, it looks pretty easy with the right tools, so I might go for it anyway. Assuming I need to tow 1000 pounds and load up another 1000 in the truck, you think that's in the severe duty range, or just regular / heavy duty?

Is it important to this whole situation that the air conditioning system doesn't work on this truck? I don't hear anything clicking on, no changes when I switch from A/C to regular fan.

These systems with overflow tanks are self purging, as described.

When refilling most systems you remove 1 heater hose and fill thru rad until coolant comes out heater core/hose, then reattach hose.
Top up rad and put cap on.

Any remaining air will be pushed to top of rad and stay there, then when engine heats up air will be forced out, and coolant pulled back in on cool down.

If the there is a blown gasket then air just keeps getting pumped into cooling system, so you can never purge it, which reads like the issue.

Yes pulling the fuel pump relay is fine.

Small head gasket leaks don't show up much on compression tests, only a few pounds of pressure difference.

If glove doesn't move then next step would be to heat up engine and rad, then shiut down and pull fan shroud off and back towards engine.
Run you hand over radiator surface, should be nice and warm all over, no cool spots, cool spot is blocked tubes.
Fan clutch works from radiator heat not engine heat, if rad has blocked tubes in the center then fan clutch never gets hot so never fully engages.

Rad should get cooler towards the bottom but only 15deg cooler not cold.

Feel upper rad hose and then lower rad hose, 15deg difference.
If lower hose is cold then either rad is plugged or water pump impeller has worn down from electrolysis.


If you do have the bouncing Glove then you can patch it temporarily, and the temporary is just that, a day or a year, there is absolutely no way to tell how long it will last.
I have used Rislone and it does work for small leaks or cracks, follow directions, for sure.
No it does NOT clog heaters or radiators, that isn't the way it works.
It is a "liquid glass" that turns to a solid when heated above 1,200degF, like in a firing cylinder, so only place it can "clog up" is at the leak point in the cylinder.

And you must leave it in because it will leak then reseal and leak then reseal.

So, this is all fantastic information. And after some tests just now, I'm cautiously optimistic that I will only need to go as far as the coolant flush. The glove test showed no movement, although it certainly inflated after about 5 minutes of idling and me squeezing the hoses. But the real problem turned out to be a seriously clogged overflow hose to the reservoir - so much so that as I was flushing out the reservoir, I had to unclog the hose about 3 times to get all of the rust and gunk out of the way. I'm going to do the full coolant flush on Wednesday and will report back afterwards, but there's no way that any amount of vacuum would be able to pull anything out of that reservoir, and I was reassured that I heard a nice sucking sound when I detached the reservoir hose from the radiator neck to get things started.

I will also note that the fan spun up to a faster speed for the first 10 seconds or so after starting it up, and then quieted down, as expected. So hopefully that means things are working as expected on the fan clutch side.

More updates to follow in a couple of days - this could just be the first of many problems.

Fan should not quiet down that quick IMO. We put the HD clutch on mine, sounds like a military Jeep for a good while until she's up to temp. BTW my fan did same as you as describing. Fan clutch is pretty cheap insurance imo

Good news about the Glove test

That's about right for the Ford fan clutch.
Ford fan clutch will be locked after it sits for a few hours, so at start up you will hear it grabbing lots of air, then in 5 to 15 seconds it will unlock and quiet down.

There is a bi-metal spring on the front of the fan clutch, as it gets warmed up by radiator heat it causes fan to spin closer and closer to water pump speed.

Fan clutch failure symptoms are about air flow not RPM.
While raising the RPM increases flow and will cause better coolant flow it won't reduce the temp as much as vehicle speed when fan clutch is failing.
Increasing temp while stopped, and lower temp while moving would be the sign of failing fan clutch.
Not while "idling" which is RPM.
So if coasting down a hill at 40MPH "while idling" doesn't cause temp to climb then it isn't a coolant flow issue/RPM issue.
That's why it can get confusing, air flow or RPM

Okay, sounds like that fan clutch might not be definitively working, but I will give it a check after the flush. Given how much crud was in the reservoir, I wouldn't be surprised if there were obstructions elsewhere, too. But the heat works eventually, so that's encouraging. I'm hoping the overheating was due to having too much air in the system, since it wasnt able to pull a full gallon of coolant out of the reservoir.

You can Back Flush heater core.
Google: backflush heater core

Very easy to do, you can also fill core with warm water CLR mixture(or vinegar) and let it sit for 15 min. then flush and repeat as you see fit

You can tell if core is plugged up just using the garden hose to flush it

Already in the works. Bought the coolant flush kit to add a tee to the heater inlet hose. I will run some coolant flush liquid through the system and then give it a thorough flush with the hose. Hopefully that does it. While it soaks, I've got lots of lower priority fixes I can tinker with.

A tee in the line may not purge the heater core the flow must be directed into the core Per Ron's advice , luck !