I recently purchased a 2000 f150 5.4 4x4 (770 bifuel series). Has 160k on the odometer. The truck runs very well, with the exception of on occasion, the shift lever will read P and it'll be in R. Only had to experience that once to remember to double check!

I decided to replace the oil filter adapter gasket as I had an annoying oil leak. Doing so, I drained the coolant and noticed that it was brown. Something I have never experienced. I took a look in the resivoir and noticed that there too the coolant was brown and there was almost.... Scaling, for lack of a better word; on the walls of the resivoir.

Puzzled and concerned I removed the resivoir, threw some water and purple power in there and gave it a good shaking. When pouring out, I placed my hand under the stream and caught what seemed to be rocks at first. When rubbed the build up breaks up into a fine paste.

From searching the web I've found that dexcool could be the culprit?? The motor runs fine, I know there's a chance of exhaust leak and head gasket failure with these symptoms just wanted some feedback.

Will post pictures...

Thank you in advanced for your time and consideration,

Adam.

 

Could have been some kind of stop leak additive...
Wouldnt hurt to do a flush on the whole system. Just one of those things you do when you buy a used vehicle. Change all the fluids and check up on maintenance items like plugs and fuel filter.... Go through and give the maf, iac and if your feeling worthy, a throttle body cleaning. Then enjoy the next 100k.