1998 Cadillac Catera, Brown antifreeze
Replaced lower waterhose... noticed after adding new antifreeze that it turned dark brown. Also noticed a slight white oily coating on the underside of the cap. I suspect a slight head-gasket leak. Do you think retorquing the heads will relieve the problem?
unfortunately no. find out which bank is the guilty party (inspect plugs) and replace the head gasket. Before you go the distance though, you mat want to stop by a GM parts dept. and buy a pack of coolant stop leak pucks, about $10. drop then all in a COLD cooling system, if it is a minor leak. these will likely solve the problem. on a side note the foam may also be attributed to moisute content as well, chanve the PCV valve if you havn't already done so.
The first basic question I would ask is; are you sure that the previous owner did not use the wrong coolant? GM uses only DexCool type coolant. If you accidently mix that with Prestone or other Non-Dexcool coolants it will result in a brown sludge that is very difficult to get rid of. I had this happen in another GM car that I owned and I had to use two containers of cleaner that you put into the cooling system and drive for a couple of days and then have the coolant replaced. This clears most of the sludge to allow the cooling system to function close to normal.
In the experience I've had with this issue, people buy the GREEN propolene glycol antifreeze, put it in then when it needs more later, they mistakenly buy the ORANGE silicate free antifreeze for newer Cadillacs, and others, put it in, then it turns brown. This could be the problem, or it simply needs flushing, to remove the dirt in the system. If the mixture is mixed, I suggest draining the system, and replacing the antifreeze, as soon as possible.
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