Is There An Auto Mechanic In The House?

[Edward]

I am mechanically inclined and have tools, but I am not an auto mechanic. I hate working on motor vehivles and the only reason I ever do is because I have to, I can't afford to hire someone.

But anyway I have an F250 with a 5.8 8 cylinder and it is driving me batty. Ever since I bought this truck back in 2010 I think, every time I had been driving it and checked, the coolant was down in the radiator. I looked and looked and I could not find a leak. So I changed the radiator cap figured it was weak. I still had to keep topping off the radiator. But I had heat and the engine never over heated, not even once.

About a year n a half ago, I accidently felt that the passenger side floor board was wet. Eureka, it must have a bad heater core. But I put it off because I was working full time and had a company truck to drive. But now that's over so I set about replacing the heater core. It wasn't that hard to replace. I drove it for a few days to make sure no leaks before dumping in new expensive antifreeze. I found low coolant, and did find a leak on a coolant bypass hose. They wanted 50 bucks for the kit so I tried some hose by the foot to make it work. It had been laying against some metal and the vibration made it leak. I tried and tried and couldnt make bulk hose fit right. I broke down and paid the 50 some bucks for their coolant bypass kit and then it slipped right in and only a slight tweaking got it up off of the metal so it wont make it start leaking again.

Filled it water to make sure no leaks again...it was ok for a couple days but today the coolant was low again. I topped it off, ran it until warm and no leaks could be found. Connections are good, hoses good, heater core new, newish cap, no radiator leaks...what the heck else could it be? I have checked every hose, every connection...I can't find even a teeny leak.

What else could it be? Please help me with an idea!

It's a 1995 F250 with a 5.8 motor (351W).

 

[JohnDB]

Radiator leak...the seals get bad after a while.

Check to see if overflow tank is rising and falling as it should. Be sure to not open the radiator when hot. But fill it and your reservoir.

If it is, then it's just because the water under pressure at 220°F will evaporate.

Be sure to check out the oil and make sure it ain't looking like coffee with milk. (Cracked head gasket)

Check your water pump for leaks too. Gaskets can go bad and when the bearings go bad it will leak too. Grinds a hole in itself.

But the radiator is metal and plastic...it usually fails after 20 years or less. Even if it isn't leaking in the middle...it leaks around the sides.

 

[WalterandDebbie]

I am mechanically inclined and have tools, but I am not an auto mechanic. I hate working on motor vehivles and the only reason I ever do is because I have to, I can't afford to hire someone.

But anyway I have an F250 with a 5.8 8 cylinder and it is driving me batty. Ever since I bought this truck back in 2010 I think, every time I had been driving it and checked, the coolant was down in the radiator. I looked and looked and I could not find a leak. So I changed the radiator cap figured it was weak. I still had to keep topping off the radiator. But I had heat and the engine never over heated, not even once.

About a year n a half ago, I accidently felt that the passenger side floor board was wet. Eureka, it must have a bad heater core. But I put it off because I was working full time and had a company truck to drive. But now that's over so I set about replacing the heater core. It wasn't that hard to replace. I drove it for a few days to make sure no leaks before dumping in new expensive antifreeze. I found low coolant, and did find a leak on a coolant bypass hose. They wanted 50 bucks for the kit so I tried some hose by the foot to make it work. It had been laying against some metal and the vibration made it leak. I tried and tried and couldnt make bulk hose fit right. I broke down and paid the 50 some bucks for their coolant bypass kit and then it slipped right in and only a slight tweaking got it up off of the metal so it wont make it start leaking again.

Filled it water to make sure no leaks again...it was ok for a couple days but today the coolant was low again. I topped it off, ran it until warm and no leaks could be found. Connections are good, hoses good, heater core new, newish cap, no radiator leaks...what the heck else could it be? I have checked every hose, every connection...I can't find even a teeny leak.

What else could it be? Please help me with an idea!

It's a 1995 F250 with a 5.8 motor (351W).

I am mechanically inclined also, well after reading the above, at least I have had some experience with the same problem, and I found that model runs funny, esp. when the thermostat opens while running.

you would have to make sure that the radiator stays full, and hot enough, let me ask you, did you make sure of that? because you said:

Filled it water to make sure no leaks again...it was ok for a couple days but today the coolant was low again. I topped it off, ran it until warm and no leaks could be found. Connections are good, hoses good, heater core new, newish cap, no radiator leaks...what the heck else could it be? I have checked every hose, every connection...I can't find even a teeny leak.

Not if because the cooling system was leaking from the tailpipe, even not running hot losing water or coolant, please check.

 

[jasonc]

buy a pressure tester or rent one and put pressure on the system and you should be able to find the leak.

 

[Edward]

Radiator leak...the seals get bad after a while.

Check to see if overflow tank is rising and falling as it should. Be sure to not open the radiator when hot. But fill it and your reservoir.

If it is, then it's just because the water under pressure at 220°F will evaporate.

Be sure to check out the oil and make sure it ain't looking like coffee with milk. (Cracked head gasket)

Check your water pump for leaks too. Gaskets can go bad and when the bearings go bad it will leak too. Grinds a hole in itself.

But the radiator is metal and plastic...it usually fails after 20 years or less. Even if it isn't leaking in the middle...it leaks around the sides.

The overflow tank has not been rising and falling.

The head gaskets are ok. I have played that game before.

water pump is no leaks and no noise. I replaced that in Colorado maybe 4 or 5 years ago.

I looked all over that radiator today real good and didnt see a drop or any rust or any thing. If it's leaking on the sides then I would be able to see water showing up. And today, it held 20 lbs of pressure for 10 or 15 minutes. Didnt budge the gauge, and that was right through the radiator cap!

 

[Edward]

buy a pressure tester or rent one and put pressure on the system and you should be able to find the leak.

I did that today! It held!

 

[Edward]

The overflow tank has not been rising and falling.

The head gaskets are ok. I have played that game before.

water pump is no leaks and no noise. I replaced that in Colorado maybe 4 or 5 years ago.

I looked all over that radiator today real good and didnt see a drop or any rust or any thing. If it's leaking on the sides then I would be able to see water showing up. And today, it held 20 lbs of pressure for 10 or 15 minutes. Didnt budge the gauge, and that was right through the radiator cap!

That would be a head gasket? There is no water in the oil...

??

 

[KevinK]

Is there any white vapor coming out the exhaust?

 

[JohnDB]

The overflow tank has not been rising and falling.

The head gaskets are ok. I have played that game before.

water pump is no leaks and no noise. I replaced that in Colorado maybe 4 or 5 years ago.

I looked all over that radiator today real good and didnt see a drop or any rust or any thing. If it's leaking on the sides then I would be able to see water showing up. And today, it held 20 lbs of pressure for 10 or 15 minutes. Didnt budge the gauge, and that was right through the radiator cap!

Ok...
If you aren't getting any rise or fall to both the overflow tank or temperature gauge your thermostat is stuck open. All the pressure is coming from your pump.

Not good. Granted you aren't overheating but your engine isn't getting hot enough soon enough...and possibly you might even have had an air bubble by your thermostat before...which causes overheating to begin with.

You might not see rust but you should see coolant leaking somewhere...
Stop using water and use coolant instead so you can eyeball the leak or whatever.

 

[JohnDB]

One other thing to check is where the water hose splits for the heater and engine. (Some goes to the heater core and some to the engine. It's buried down low by the firewall.

That might be where you have a slow leak. Had that happen once as well. My old Ford trucks have always had radiator issues...so did my Pontiac.

Them overflow tanks only fill after a good hot run on the interstate. An old plugged cap can blow out the seals on a good radiator so keeping an eye on the overflow tank is important when stopping for gas. Also check the drain plug on the bottom of the radiator. It can leak too.

 

[Edward]

well up until now I have only filled the radiator. This time I also put water in the overflow tank to the cold fill line. I didn't think it would make a difference before. The stat is only 4 or 5 yrs old too but I suppose it could be bad again.

I just checked it again and the oil is clean and nothing abnormal at the tail pipe.

Not having a garage here sucks.

 

[Edward]

One other thing to check is where the water hose splits for the heater and engine. (Some goes to the heater core and some to the engine. It's buried down low by the firewall.

Do you mean the coolant bypass? That's all new.
and the heater core connections are high and visible.

 

[KevinK]

There is one other common problem with the 351W engine. Apparently there can be coolant leak from the timing chain cover. Either the gasket blows, or the bolts or aluminum housing itself corrodes enough to cause leakage.

 

[Edward]

Ok...
If you aren't getting any rise or fall to both the overflow tank or temperature gauge your thermostat is stuck open. All the pressure is coming from your pump.

It did heat up faster before, and while I did check the heater I didn't really pay attention to how fast it heated up. It didn't seem to take very long today and I did run it on the interstate.

I guess I'll pick up a new T Stat for it. That;s an easy change and we'll see what happens then. Even if it is stuck open though, it shouldn't make it lose water, right?

 

[Edward]

There is one other common problem with the 351W engine. Apparently there can be coolant leak from the timing chain cover. Either the gasket blows, or the bolts or aluminum housing itself corrodes enough to cause leakage.

It should dry real good tonight and tomorrow I'll slip some cardboard under it to see if any drip show up when I run it for awhile.

 

[KevinK]

See any yellowish residue around that area now?

 

[JohnDB]

It did heat up faster before, and while I did check the heater I didn't really pay attention to how fast it heated up. It didn't seem to take very long today and I did run it on the interstate.

I guess I'll pick up a new T Stat for it. That;s an easy change and we'll see what happens then. Even if it is stuck open though, it shouldn't make it lose water, right?

Stuck open can make the water evaporate...steam is all that hits the overflow tank. Not quickly...but over two days? sure it's possible.

 

[Michael74]

They make dye that you can put in to make tracing leaks easier.

 

[jasonc]

There is one other common problem with the 351W engine. Apparently there can be coolant leak from the timing chain cover. Either the gasket blows, or the bolts or aluminum housing itself corrodes enough to cause leakage.

351 will do that but oil would have mixed with oil

Stuck open can make the water evaporate...steam is all that hits the overflow tank. Not quickly...but over two days? sure it's possible.

Reverse ,a stuck open t stat would lower engine temp,and take longer to heat the block.Nissan of mines fully open at 160.

In the cold at 0 I can use the heater in 3 minutes,stuck open which it happens nope more like an hour

Also check coolant to water ratio . water will evap quicker then antifreeze .

 

[jasonc]

If truck has obd2 a code for t stat would possibly show