So I took my car to the shop today and they told me that there is combustible material in my coolant. They said that it is probably a bad water coolant seal and were not sure on how much it would cost to replace it. Any idea on how much this would cost from anyone who has had this done before?

 

The cost of a full tear down.

around 1k if you do it yourself.

probably 3-5k at the shop.

 

Are you loosing coolant or is the car overheating?

 

This is the correct question.

If the car isn't overheating and your coolant isn't noticeably disappearing the motor can keep going for quite awhile with a dying coolant seal. (Mine did).

Your only other option is a complete tear down. I know people who have taken the whole motor apart just to do coolant seals but it is obviously a lot of work and for me at least (This just happened to me) I decided to do a full rebuild because... well, the whole motor is apart.