Have a 383 stroker that was running hot. Bought a new radiator, water pump and thermostat. When I pulled the old thermostat out I noticed a white jelly looking substance stuck to all the walls of my intake manifold. What is this and what is the best solution to clean it off? Should I take the manifold off to clean it or run an agent through the cooling system that will clean it.

 

sounds very similar to the classic symtoms of mixing dexcool and green antifreeze. its a total no-no. it will fill your entire coolant system with that gelatinous build up.
i'd suggest flushing your coolant system very good. then put a gallon of a degreaser in it like mean green or similar, top off with water, run it for 10 minutes, then flush it all out.
get some weedeater line and fish it in the coolant passages to loosen the stuff up. might even pull the block plugs on the sides and fish around in there.
then pour a gallon of vinegar, and top off with water. run it for 10 minutes to clean everything out. flush with water again.
fill with your favorite green antifreeze and distilled water.
stay far away from the orange dexcool, and never mix the two.

 

Good advice from redneckjoe. Let me add this: an old radiator shop told me this many years ago - 1 cup of Lestoil to clean and filled with water. Drive it for a day as long as the temperatures do not go below freezing that day! Then water rinse as many times as necessary to run clean. Then fill with your favorite green antifreeze and distilled water. Lestoil available at Lowes in the cleaning products aisle.

 

1. What kind of coolant are you using?

2. If it's a concentrate, are you mixing it with tap, bottled or distilled water?

3. If you're mixing with tap water, how hard is the water in your locale?

4. Did anyone put any kind of additives (wetters or sealers) in the cooling system at anytime?

 

Use distilled water. Its only a couple of bucks for a 4qt jug. Never use tap water. If you dont want to bother to mix you can buy pre-mixed coolant. The down side is it is almost as expensive as regular, so it will cost twice as much. Some people cant figure out how to mix coolant, hence the premix.

tap water is fine for flushing, cleaning or getting you home. For the 4 bucks it would cost to use distilled I think its worth it.

I have used water wetter agents in my trucks for pulling our big trailer. Did it make a difference? Couldn't tell on the gauge and there was no noticeable difference. Wetting agents are most effective with a 100% water only coolant. The more actual coolant you add to the mix, the less effective they become. Most companies will have a temp drop chart with various coolant mixtures as a reference.

Sealers......if you are tired of chasing a stubborn leak, going to sell it and send the car on down the road, then fine. If its a car you are keeping, then properly fix the leak Dont poor crap in it and try to fix it. Sealers are not smart enough to know what leak you want fixed. So they gum up rads, heater cores, restrict smaller coolant passages, etc. I have torn down too many engines with that crap in it. It doesnt fix anything, just masks the problem. When ever I see that stuff on the shelf I always think of the guy flippin cars for cash and passing problems along to the next owner. I know some people on here may disagree, but if you were paying me to fix a leak, would you personally accept that as "properly repaired"?