dyera1

I just rebuilt a 1968 dodge 318 engine. It drove fine during the test runs but while driving home for the first time she shut off and was overheating. radiator hoses were so hot!. When i popped the hood i saw white smoke coming from the intake manifold to cylinder head, gasket. it also looked like white smoke was coming from underneath the valve cover, but not sure. PLEASE HELP! The current set up is an Edelbrock Preformer intake on a 68 318 bored out 30 over. new valve job and valve seals, new Gaskets all the way around, and new water pump. what could have caused this? bad pump? it smoked on both sides of the manifold which is making me confused. the radiator to engine settup is a little different than usual with longer hoses than usual. HELP

TVLynn

I would start by checking that all of the hose connections are tight, Check and make sure the thermostat is not installed upside down. Make sure you didn't get a magnum water pump serpentine belt turns it oposite I think ???

Coronet 500

I'm wondering how long were the test runs compared to the drive when it failed. My first thoughts are air pocket in the engine and/or faulty thermostat. I would remove the stat and boil it in a pot to see if it opens. When I first fill smallblocks I use a short hose at the pump heater hose with a funnel and another short hose at the manifold heater hose. When fluid comes out the manifold hose you will know the block is completely filled. Filling the heater core before attaching hoses will remove air from it aswell.

Do you have a temp sensor in the manifold?

dyera1

I will check the thermostat this afternoon. water pump rotation has been checked. thanks.

dyera1

The test runs were 2, 15 minute drives where I went from 0-55mph six or seven times. The drive home was a 7 min 3 mile drive in normal traffic.

440roadrunner

This could EASILY be an airlock. To fill any traditional / vintage engine, remove the heater hose immediately under the thermostat. Fill "until you get water." On the Mopars I try to remove that hose at the heater rather than the engine, as I can prop the hose up higher, and get more coolant in. "Dip" the hose into a container to confirm you have water "up there," then hook back up to the heater.

ALWAYS when warming an engine after a re-fill run for a bit with the heater engaged, and constantly feel the heater hoses BOTH of them which should get very warm even before the stat opens.

It has become popular to drill a bleed hole in the flange of the thermostat, and I'm sure this helps as well. Some stats come this way.

Also, on most engines, when the coolant is airlocked, the temp gauge is very slow or unresponsive

I hope you have not hurt anything

Archer

d -

Always do the easy checks first.

Carefully feel all four quadrants of the radiator, they should be about the same temp. (An IR thermometer comes in real handy here.).

Once cool, open the cap and watch for water flow.

However, what you are describing is usually a frozen thermostat. If you bought a Mr. Gasket T-stat, then it's almost certain...

Seriously, remove the housing and the t-stat, drop on a new gasket and retest. If the temp stays within reason, get a Stant 180* t-stat and you're done. If the engine is worked, you can drop to a 160 for faster opening.

If that's not it, then there's a blockage in a water passage. (The blockage may be solid or air). Running the engine from cold with the radiator cap off might solve an air gap, but if it's solid, you'll have a full flush in your near future.

Archer

dyera1

What I have done; Drained then radiator fluid from the lowest end of the radiator, removed thermostat housing, (Fluid gushed everywhere and thermostat was in correctly), boiled thermostat, (Didn't start to open until water was was really boiling), under the thermostat was some brown grime. Nothing thick though. The temp light never came on during the last drive but I want a way to test it as we'll. Any ideas on where to go from here?

dyera1

So I removed the stat and started her up. No smoke and ran perfect, for now. Got evenly hot throughout the radiator. One small seep from under the stat housing. Buying an o-ring to replace that this evening. Thanks guys. I will let you know if anything else developes.

pro-tech

So what you are saying is the thermostat is bad? If its OK with the thermostat out.. When you get the new stat drill a 1/8" hole in the flange of the thermostat like 440RR said and that will eliminate air pockets. Unless you have an air lift tool to add coolant and you probably dont so the hole is the best option..Keep us posted...Bill

dyera1

Yes the stat was bad. But here is what I also found. Being a custom setup engine i didn't have a radiator fan housing (stupid me!). Since my new radiator is inset further forward I just think I was producing enough vacuum drawing in cool air. My fan already has a 2inch spacer on it, to get it closer to the radiator, and since finding a custom dimensioned housing may be hard to find, I purchased two 12" electric cooling fans. The kit didn't come with a housing but side by side they will fit perfect and I can block off the rest if I need to. I also purchased and installed a temp gauge. In three days I should have the truck together and on the road for a test.