found some tan gunk in my rad fluid. changed out the tranny oil .. thought it looked a bit milky after a ride, drained it and it looked fine. Took off rad cap and found this tan gunk onder the cap. drained the fluid and the fluid looked great but said gunk dribbled out after the rad fluid. not much but its in there. where should I start looking?? water pump seal? head or base gasket??

do you have to have a pic on another site to post them here??

is there a way to tell if the water pump seal is leaking when the pump cover is off and the impeller is off?? would you see any seeping around the shaft. I cleaned up around the seal and did not notice any corrosion. There was plenty of gunk in the nieghborhood though. seal itself looked pretty good. tranny oil is nice and clean. If th epump seal is leaking shouldn't it leak rad fluid into the tranny. Not tranny oil intohte radiator??

Hi Skidmeister,

Are you having a cooling problem or just stressing over a something a little odd? Almost any time you have metal and fluid in contact in a hot engine they're gonna cook up something unpleasant. Could be residual gasket goo or assembly lube or myriad other things. If the fluid looks good that's a pretty good sign that there's nothing major going on. It sounds like this tan gunk is floating on the top of the coolant which would indicate it's not water soluble i.e. oil or some kind of polymer. First step is drain and refill with good coolant preferably something that is magnesium friendly (propylene glycol) like Engine Ice, Maxima Coolanol, or Silkolene Pro Cool. Ride for a while and see if there is the same amount of goo. It may be this is something that is just leaching out of the system and is relatively harmless. To be honest unless the thing is spitting steam out I rarely look at my coolant and then I'd have to see something really funky with the coolant to get me worried. A little scum on the surface I expect. Ewwwwwww!