Cooling system leak
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Junior User
Joined: Apr 2003
Posts: 50
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From: Nanaimo B.C.
Cooling system leak
High guys,
I've got a problem. I own an 87 F150 4.9 truck that has developed a leak in the cooling system that I can't find. The engine never oveheats even with the fluid level down. I replaced the heater core, one thing I noticed though is that when I take the rad cap off now after running the engine it hisses which it didn't before so I am assuming the system is sealed which it wasn't before. Another thing I did was fill the rad up to the very top of the neck and now I am wondering if that was to full. The coolant appears to be most prevelent under the oil pan on the ground. I recently replaced the heater core, but that doesn't appear to be the problem, since I pulled the cover off and checked it and there was no fluid anywhere. Also the overflow res doesn't want to stay full. I checked my oil and it apprears to be alright so I don't think it's the head gasket. Anway any any ideas or suggestions would be appreciated.
Thanks in advance
F.O.G.
I've got a problem. I own an 87 F150 4.9 truck that has developed a leak in the cooling system that I can't find. The engine never oveheats even with the fluid level down. I replaced the heater core, one thing I noticed though is that when I take the rad cap off now after running the engine it hisses which it didn't before so I am assuming the system is sealed which it wasn't before. Another thing I did was fill the rad up to the very top of the neck and now I am wondering if that was to full. The coolant appears to be most prevelent under the oil pan on the ground. I recently replaced the heater core, but that doesn't appear to be the problem, since I pulled the cover off and checked it and there was no fluid anywhere. Also the overflow res doesn't want to stay full. I checked my oil and it apprears to be alright so I don't think it's the head gasket. Anway any any ideas or suggestions would be appreciated.
Thanks in advance
F.O.G.
Tuned
Joined: Feb 2003
Posts: 495
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From: Cincinnati, Ohio
Might be the water pump or a hose. I would have the system pressurized so that nyou can locate the problem. Usually you can detect leaks just after turning the ignition off after the system has reached thermo temperature and has built up pressure. Drive the truck a few miles and then shut it off and look for the leak. Look from under the truck up at the water pump to see if that is your problem. Check all hose clamps and at hose attachment points for a leak.
John
John
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Junior User
Joined: Apr 2003
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From: Nanaimo B.C.
Thanks
I think I found the leak. It appears to be the lower hose at the block. The strange thing is that it doesn't leak when the system is cool, just when it's hot and under pressure. I guess I'll try tightening the clamp first since the hose looks pretty good. And if that doesn't work I'll replace it. I also wonder if the rad cap is no good since the system doesn't seem to go to the overflow. Anyway just a thought and once again thanks.
F.O.G.
I think I found the leak. It appears to be the lower hose at the block. The strange thing is that it doesn't leak when the system is cool, just when it's hot and under pressure. I guess I'll try tightening the clamp first since the hose looks pretty good. And if that doesn't work I'll replace it. I also wonder if the rad cap is no good since the system doesn't seem to go to the overflow. Anyway just a thought and once again thanks.
F.O.G.
Posting Guru
Joined: Dec 2002
Posts: 1,113
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From: Remsen, NY
Hoses will start to leak like that when they start to go bad. The inner layers develop leaks and the coolant runs up along the reinforcing fabric and out of the end of the hose. It's a good early warning of a major hose failure. And those hoses are about $20 at NAPA IIRC. Clamping harder will only delay the replacement if it does anything.
Also, I haven't seen this talked about much. You can go to NAPA and buy a little bottle of UV dye to put in the coolant. Then, with tiny leaks you can't find, the dye will leak out and mark where it's leaking. Then you just get one of those little ultraviolet penlights (leak detection) from the air conditioning section of Autozone or whereever and go looking when it's dark. The tiniest leaks show up this way.
Also, I haven't seen this talked about much. You can go to NAPA and buy a little bottle of UV dye to put in the coolant. Then, with tiny leaks you can't find, the dye will leak out and mark where it's leaking. Then you just get one of those little ultraviolet penlights (leak detection) from the air conditioning section of Autozone or whereever and go looking when it's dark. The tiniest leaks show up this way.
