Is this normal, or is something wrong? The coolant is clean, the scum isn't on top of it, just on the inside walls. It's slight, not heavy, but looks brown on my finger when I scrape it on the inside. Thanks!

 

Is your engine oil dipstick clean?
That is indicative of oil in the coolent. Also check the transmission lines, you could be having a leak from them to the radiator. Also, what model? This could also be a leak in the cooling pockets for the transmission. It also could be residue from a previous issue, little history on your car.

 

Thanks, for your reply. My ride is a 2006 Uplander. I just bought it recently. I talked to one of the local parts people yesterday, and he told me a little scum is normal for an older vehicle. However, I like having second or third opinions. I will check the tranny fluid tomorrow to see if there's any moisture in it. How do I check the transmission lines to find a rad leak? I checked the engine dipstick and there is no indication of water drops or milkiness, although the oil is dirty, and the dash board tells me it's 50 percent used up. The actual coolant is pristine, almost brand new. I was worried about a leaking head gasket because my last two vehicles had this problem. I use my van in my landscaping business and I take my van on a lot of really short trips. The condensation coming out of it was extremely heavy, and worrisome. However, yesterday, when the weather was extremely wet and only several degrees above freezing, I took it for a long drive. Once the engine was good and hot, I parked it and took a look. The exhaust was dry and invisible, and there was no water dripping out of the pipe. So I don't think the coolant is leaking into the combustion. I suspect I'm just overly paranoid about head gaskets.