I don't know if anyone does autopsies like I do when I remove a failed part, but I thought I'd share this one. When I bought my '97 Aerostar 8 years ago, I noticed some brown gunk floating in the coolant. Not a whole lot, just a few specks here and there. I did a drain and fill several times but then I noticed that it ran warm on warm days (80F and up). When pulling the motorcycle trailer up some grades with temps in the mid 90's or cruising down I5 to California in the summer, the temp gauge would get up to the "R" or "M". It usually didn't go over the "O" and the old 4.0 would never get past the "O" under similar conditions.

I replaced the radiator about 7 months ago and tore the old one apart. I saw where the brown gunk was coming from. I can only assume the previous owner had used radiator sealant. This gunk had completely coated the radiator and plugged up a good number of the passages. Also, there was a good (bad) coating on the tranny cooler. Cooling capacity was probably reduced by 30% to 40%. I'd post an image to illustrate, but I can't figure out how to do it.

I went over to the hot part of the state for the last weekend in June and the temperature gauge never got above the "O" with temps in the mid 90's with the new radiator. And this was with the wimpy single row radiator for the 3.0.

If you're thinking about using radiator sealant, think twice. I hate to think what the rest of the cooling system looks like, but at least it seems like the cooling capacity is adequate now.

 

All cooling system sealers are just stop-gaps to deal with an immediate problem, and should not be used for extended periods of time. One of my cars had sealant from the previous owner, and I found it when I was flushing the cooling system. The sealant got flushed out and it started leaking. Some sealants are a lot worse than others for clogging radiators or heater cores. Also, those hoping to seal a head gasket leak will be disappointed. The sealers only work on leaks to the open air, not against combustion chambers that will generate more than normal radiator pressures.

 

these goldenseal plant and other snake skin quicky fixes also plug up the not fun to replace heater cores

I had to replace both the front and rear H. cores after using the goldseal tabs trying to stop a top front engine leak. not a fun or low cost job and in the winter time