coolent loss
#1
09-29-2012, 09:54 AM
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coolent loss
1991 F-250, 302, 150,000 miles. Coolent is disappearing with no evidence of leak outside engine. In mornings after driving previous day overflow is empty and radiator is down on fluid slightly. Truck runs well and shows no unusual exhaust emissions. I am not a mechanic and haven't found a good one. I have some ideas about problem but can't afford to make any mistakes. I can't determine if there is coolent in the oil. Where should I begin to find the cause? Should I park this truck until this is fixed?
#2
09-29-2012, 10:21 AM
Fleet Mechanic
And yes, stop driving the truck or you will trash the engine bearings. Coolant makes a horrible engine lubricant.
#3
09-29-2012, 11:05 AM
You should drain the oil into a clean container and do a visual inspection.It's free and easy to do.It doesn't take alot of coolant to discolor motor oil.It is possible that you have a small external leak.Rule out the internal leak first.To find the external leak,you'll have to get the engine to operating temp and crawl under an take a real good look.You'll find it.Fill the rad before checking for the leak.How much coolant can you put in the rad after a day of driving?This will also determine the severity of the loss.
#4
10-03-2012, 09:09 AM
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Coolent loss
I am at sea on this one. The coolent loss is minor but consistant. There is no white residue on the filler cap. The dip stick does show overfull. The oil seems to be OK. However when hot the oveflow tank level is not rising. Cold the radiator is full. It has a newer rediator.
Last night my son and I took it for a 30 mile mostly city drive. From the shot-gun he observed a tic in the engine I couldn't hear, some gray smoke from the exhaust which I couldn't see and that the engine was loping sometimes in high gear at low speeds up hills. I could feel the loping in the gas pedal. Full power was fine. After we got back I could smell something burning (electrical type smell) and saw some vapor from the engine compartment but was unable to find the source. Truck has newer plugs and a new computer.
I must take it to a mechanic but would like to know what they should do next; a compression test for example or what? I cannot affford to make a mistake and need this truck to pull my RV.
Last night my son and I took it for a 30 mile mostly city drive. From the shot-gun he observed a tic in the engine I couldn't hear, some gray smoke from the exhaust which I couldn't see and that the engine was loping sometimes in high gear at low speeds up hills. I could feel the loping in the gas pedal. Full power was fine. After we got back I could smell something burning (electrical type smell) and saw some vapor from the engine compartment but was unable to find the source. Truck has newer plugs and a new computer.
I must take it to a mechanic but would like to know what they should do next; a compression test for example or what? I cannot affford to make a mistake and need this truck to pull my RV.
#6
10-04-2012, 05:06 AM
Posting Guru
It could also be the timing cover gasket.
You can do some diagnostics yourself, for free. Autozone and most other chain stores like them rent tools. Get yourself a cooling system pressure tester. It installs in place of the radiator cap, and pressurizes the cooling system. At that point, when the truck is cool, you can pressurize and check for leaks. This tool also has a gauge on it, so you can see how fast the pressure is going down, or once you've done your repairs, if it holds pressure.
At Autozone, tool rental is free. You pay for it up front, but get all your money back when you return it.
You can do some diagnostics yourself, for free. Autozone and most other chain stores like them rent tools. Get yourself a cooling system pressure tester. It installs in place of the radiator cap, and pressurizes the cooling system. At that point, when the truck is cool, you can pressurize and check for leaks. This tool also has a gauge on it, so you can see how fast the pressure is going down, or once you've done your repairs, if it holds pressure.
At Autozone, tool rental is free. You pay for it up front, but get all your money back when you return it.
#7
10-04-2012, 09:13 AM
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In search of .....
Duncan, I went thru a similar problem and found 2 problems on my 351 W ... first was the radiator cap #2 was the small throttle body heater hose ... it's 3/8 I think. Down at the lower connection there was a very small leak that only showed under pressure, coolant went down the front of the block and did not pool up near the distributor. If It were me I would also make sure the heater core isn't a factor ... Good luck on your search !!!! Dave
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#8
10-04-2012, 12:48 PM
#9
10-04-2012, 01:01 PM
Fleet Mechanic
Get yourself a cooling system pressure tester. It installs in place of the radiator cap, and pressurizes the cooling system. At that point, when the truck is cool, you can pressurize and check for leaks. This tool also has a gauge on it, so you can see how fast the pressure is going down, or once you've done your repairs, if it holds pressure.
I'm not saying that you shouldn't do a pressure test, just don't take the results as anything absolute.
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