How come I check my coolant every now and then in my 1986 300-6 and it is always about the same level in the radiator. I look down the cap and it is like 6"- 8" down in the holding tank. I topped it off the other day when I was changing motor mounts and again this week it was the same. It doesn't get any lower than this though always stays the same, and also I checked the oil and it looks fine, also defiently not burning it out. Any other ideas? Shoudl it be right up to the top of the neck in the radiator? Kind of a stupid question but just curious. Oh, just FYI jsut changed the heater core earlier this last summer and pressure sems good in the system.

 

No such thing as a stupid question! I had the same problem with my 84 a couple years ago and finally found out my water pump was leaking, apparently just a little bit and only when it was running. You might want to take a look at the weep hole on the water pump to see if the tell-tale stain is there to indicate a leak.

 

Tighten/check all hose clamps. Look for any wet/antifreeze on the block. Maybe your heater core is doa. Did this just start after the heater core was replaced?

 

There are no poodles under the truck and I watched it while it runs to see if there are any fluids leaking anywhere. Even all around the block it is bone dry. Jsut kind of stratch my head over it. The old heater core was leaking, by-passed it for the summer and was still getting the same thing. No smell of coolant or anything, maybe it is the weep hole in the water pump though.

 

Can you smell antifreeze? Sounds stupid but you can if the leak is bad enough. I had the same problem with my F8. Fill the rad. 50 miles later the antifreeze disappeared like magic. Couldn't find the source of the leak. The only way I was able to solve the mystery was to add some leak detector to the rad. When the leak occurs it leaves a bright yellow/green color at the source. You can't miss it!! BTW the water pump gasket was the failure on the F8. Only would leak while driving. Kinda tough to check it on the highway at 60 mph.

 

Sometimes after you shut it off, pressure is still in the system, the rad cap releases this pressure along with the fluid to the vent pipe......just another thought to get you thinking. By the way, Fords Rad levels in the Radiator should NOT be top off at the very top. According to the Haynes manual and my experance in the past, the radiator should have at least a one inch "air" gap, meaning that coolant shouldn't be at the very top of the cap.... Also Skyline Drive has a good idea, at least you'll find the leak if there is one.......

 

I just remembered FWIW my buddies dad was a old school mechanic/service manager from the 50's,60's,70's and 80's. I remember now that he told me that older engines will seek its own collant level. FWIW

 

Makes sense about seeking its own level. I would let the ruck sit and idle for about 20 min and not the least drop of any fluid would be present uner the truck, it is really puzzling to me. Also I don't have any smell of coolant anywhere. Only time I did is when my heater core went bad. I'll have to keep an eye on it somemore.
Thanks,
Chris

 

Do you have a coolant recovery tank or just the overflow hose down to the road?

The motor's do tend to seek thier own level, so even without overheating sometimes they'll puke some water out 'till they get where they want.

My mustang always did this, coolant level was about two inches down there. I put on an overflow tank and the problem is gone. After it heats up the extra water it dosn't want goes into the tank, and as it cools down and the pressure drops a vacuum is formed and sucks it back in. Every time I check it (cool) it's full.

 

You can also pressure test the system too. Instead of idling the truck why dont you rev it to 2k rpm for a couple of mins.?

 

Chris,

The best way to find a leak in the cooling system is to pressure test it. It is best done when the motor is cold so you can look in all the hard to see areas without getting burnt.

If you are not familiar with the way it woks you simply remove the radiator cap, screw on the test adapter and then hand pump up the system to the manufactures spec. Most auto parts stores can provide the spec since they need it to sell you the right cap.

With the system under pressure and without the noise of the engine running you will probably be able to hear the source of the leak. Watch the pressure gauge on the tester and see if it holds any pressure or if it is loosing it slowly or even not holding it at all.

If you have an aluminum core/plastic tank radiator the tanks have large “O” ring gaskets that with age and the effects of hot coolant will eventually give out. The return side of the radiator is the most likely source of a gasket failure since it is much hotter than the supply side. My money is that is where your leak is occurring. And it is about 6” – 8” down from the top. Once the coolant leaks down to that level it will stop – or at least greatly slow down. Sometimes the crimps that hold the plastic tanks on can be tighten just a bit and stop the leak. Crimp it too much and you will crack the tank. Many good radiator shop can now repair those radiators. Look for one in your area.

If you can’t find a leak with the system pressurized then check that the cap is opening at the right pressure and that you have the right cap. If it is opening at too low of pressure it will belch out fluid until it get down to a certain point. The pressure tester kit also has an adapter to test the opening point of the cap.

Good luck,

Mark

 

MChild,

That's is where my radiator leaks - but only in the winter - in the summer it doesn't leak at all.

I tried to tighten the aluminum tabs on the side and it didn't help.

I will check around the local radiator shops; but, most are not interested in fixing anything - just selling a new radiator.

Thanks for the informative post.

Oscar