Coolant leak, but no idea from where...?!?

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Patrick

Patrick

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Kind of embarrassing guys - there's a small puddle of coolant below the 318 after it sits for a while and i have no idea where it's coming from... Looks to be on the passenger side mid to back engine. I touched along the head gasket and looked/touched at and near the freeze plugs - no sign of a leak. I checked the heater hoses going into the heater core - no sign there either. I looked/touched on the driver side as well as the oil pan - dry...

There is no leak when the motor runs and does not leak within ~ 1 hr of turning the engine off either... Weird!

Thanks in advance for your suggestions!
 
There's nothing embarassing about that! What I would do to start is to pressure test the cooling system...may not work cuz you say the leak happens after a hour of sit time, but its worth a shot. The second easy thing you can do is run to your parts store and and get your hands on some coolant tracer dye and pop it in your radiator, it will make locating the orgin of the leak much easier!
 
Great - thanks for the suggestions. Am i looking for an radiator cap adaptor that allows me to hook up my compressor then?
 
No, you are looking for a kit that contains radiator cap adapters and a hand pump with a gauge. Ask for a radiator pressure test kit at your local parts store. If you hook up your compressor to the radiator, you will be needing a new radiator. The leak you are describing sounds like the classic exhaust stud leak. The 2 exhaust studs at the ends of the head screw into the water jacket. If you install them without thread sealant the result is the leak you are describing. The fix is remove the studs and reinstall with sealant. Drain the radiator when you do it or you will have a big mess. Don't forget to do both sides while you're there.
 
my quarter bet is placed on leaking freeze plug. The seepage through a rusted plug is very small. The crap that has accumulated in the moisture will help hide it and promote the evaporation when the engine is hot.
 
grumpuscreature said:
No, you are looking for a kit that contains radiator cap adapters and a hand pump with a gauge. Ask for a radiator pressure test kit at your local parts store. If you hook up your compressor to the radiator, you will be needing a new radiator. The leak you are describing sounds like the classic exhaust stud leak. The 2 exhaust studs at the ends of the head screw into the water jacket. If you install them without thread sealant the result is the leak you are describing. The fix is remove the studs and reinstall with sealant. Drain the radiator when you do it or you will have a big mess. Don't forget to do both sides while you're there.
Click to expand...

Ah ha! We did have to re-tap one of the studs (I forgot about that!) so you may have found the problem... I'll take a closer look there and keep you posted.
 
RedFish said:
my quarter bet is placed on leaking freeze plug. The seepage through a rusted plug is very small. The crap that has accumulated in the moisture will help hide it and promote the evaporation when the engine is hot.
Click to expand...

This could be true too - will the dye test work well enough to isolate the leak?
 
Yup... put money on the exh stud especially if you had to fix threads.. It may stop on it's own (not sure how long you've been driving it) or a small amount of "Stop Leak" should stop it. Not the whole big pill or bottle... just a small amount.
 
moper said:
Yup... put money on the exh stud especially if you had to fix threads.. It may stop on it's own (not sure how long you've been driving it) or a small amount of "Stop Leak" should stop it. Not the whole big pill or bottle... just a small amount.
Click to expand...

I touched all around the studs and everything feels dry!?! The freeze plug isn't dry but it isn't dripping wet either.

I'll get that pressure kit and try to nail this once and for all! Been busy at work so haven't had the time yet...

Thanks guys
 
Patrick said:
I touched all around the studs and everything feels dry!?! The freeze plug isn't dry but it isn't dripping wet either.

I'll get that pressure kit and try to nail this once and for all! Been busy at work so haven't had the time yet...

Thanks guys
Click to expand...
Isn't dry? Your problem, and the rest are fixing to go. Get brass ones, from boat places.
 
Was out of town this weekend but wanted to give you an update. No leaking anywhere around the studs. Read in another post here that this could be freeze plugs behind the motor (hidden by the tranny). Again, haven't verified this yet, but since there is no visible sign from above this seems to me to be a reasonable answer... Can't pull the tranny out anytime soon so my bandaid will be to replace the 15 lb cap with a 7 lb one to hopefully reduce the pressure a little bit. Thoughts?
 
a weak system cap is meant for a radiater that has been repaired. It might buy some time before the leak gets worse but the leak will still be there.
I would suggest barrow a system tester, pump it up to about 15 lbs. and walk away for a few hours. Come back and find the leak. If by chance you should have a rare cold water leak at the water pump, you wouldn't find the leak under pressure. This leak happens at zero pressure. Its rare but it has happened. Coolant will leave a white residue trail where it runs and drys. Visual evidence. Good luck
 
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