new member here and I have a quick ???. I have a 91 with the 4.3 with 297,650 miles on it. (from what I'm told yes its the stock engine and tranny) Anyway there is white sludge on the oil dip stick and in the top of the oil fill cap. I'm not stranger to engines so at first this did not bother me since it did start getting cold here. So condensation could be the problem. Took it to a friend of mine to look the truck over (I only gave 500 for it). While I was there I showed it to him and he said the PVC valve was not working correctly. Turns out the TBI port for the PVC was clogged got that sorted out and have driven it 250 miles since. Go to check the oil and sludge still there.

The sludge is not oil water mix per-say its pure white. The oil is still well oil (in this case black I mean almost 300,000 miles) just there is lots of White sludge as well. Could it just be building up at the end of the dip stick tube. I plan to replace this engine when I get anther car to drive and pass this down to my son. For now though I need it on the road cause its my only ride.

Also I lost maybe a cup of coolent in a 2 week period but I think the heater core has a hole in it and they used some stop leak to fix it since I have little to no heat.

 

If its not mixing in the pan it sounds normal.

You just found out what stop leak is good for, clogging up heater cores and radiators. Lucky and hope its only the heater core in your case. Next time I suggest placing a valve in the heater feed line. Just manually shut the valve and it will stop it until you can replace it without clogging the system up.

 

I would pour a bottle of CLR into the rad, run it a couple hours, and flush it out. If the heater core has a leak, you will smell it in the cabin. Then replace the core if leaking, flush with water real well, and fill with new coolant. That CLR works amazing for flushing out all the crud and grime.

As for the white stuff, maybe pull a valve cover off and see how much is inside there. If none, then i wouldnt really worry about it.

It the heater core leaks, you can pull the 2 hoses off it under the hood amd join them together with a coupler to bypass the lleaky heater.