Coolant leaking

[94mustangcobra]

I've looked everywhere for an external leak, can't find one. looked at the overflow can radiator, heater core tubes, all of it and nothing. did a pressure check on the system and it's losing pressure. have to add coolant about everything 3 to 4 days. can't see it in the oil, can't smell it in the exhaust. only thing that might be is when i checked the plugs all are black (colder plugs for nitrous/rich SCT tune) except for cylinder number 6 wich is crusty white. did a compression check and all cylinders are pumping up the same and i don't have access to a leakdown tester. anymore thoughts??

 

[Vipersix]

Uhh... where is the coolant going if it's not leaking out?

You've got some odd problems if you have 7 black and 1 white spark plug. Are the black ones oily black or crispy black? White spark plugs are normally a good sign for extreme temperatures/pressures caused by excess timing, poor fuel, high compression, or a combination of all three. Of course, the fact that your compression is all the same sort of blows a hole in my leaking cylinder theory.

Hmm...

You wouldn't happen to have ensured that you are getting spark at each spark plug have you? Obviously this doesn't solve your coolant problem but it's a start at something.

The only other thing I can think of is that you have a transfer of coolant into one of your cylinders (possibly #6) and it is getting pumped out your tailpipe. This would explain the loss of coolant and the crusty spark plug. Might be worth taking off that head.

 

[94mustangcobra]

the other seven plugs are a sooty dry black not wet oily looking. but i'm gonna be pulling the intake off here shortly just to take a look and make sure it's not my intake sitting weird or whatever, but it is progressively getting worse. thanks for your reply Vipersix

 

[95Vert]

Take it to get a coolant leak test.

 

[94mustangcobra]

already been done and it loses pressure fairly quickly

 

[95Vert]

already been done and it loses pressure fairly quickly

Are your head gaskets ok? What about your intake gaskets? Check 'em out.