460 Coolant Contamination Concerns

Rebuilt 460 with 2600 miles on it.

Ever since I've had it, I get some white smoke on cold starts but then dissipates. No identifiable sweet smell. No known coolant consumption but haven't taken any reservoir measurements to really watch it closely.

After probably 1000-1500 miles I noticed some black flecks/gunk in the reservoir near the top stuck to the sides. Drained the radiator, cleaned the reservoir and refilled.

The gunk is back although not as much.
Rubbing the sides with my finger as far as it will go, I get this:

Rubbing my fingers together it has a rubbery feel. Definitely not slick or lubricating.

The coolant is the expected green color. Looking at the bottom of the reservoir I noticed a layer from the outside about 1/8 thick. Took a straw and scraped it through the plug hole:


This is more slick than the side wall stuff although one is submerged and the other isn't.

Removed the radiator cap and the coolant looked good. Upon tipping the cap to let it drip, the brown stuff (more diluted) dripped from that cup on the bottom of the cap with the rubber seal and got into the filler neck:


You can see how besides what dripped in the middle, around the outside is dirty. With no pressure and the cap sealed, this "outside" would be in the same pool as the reservior.
Running a rag in the cup area by the cap spring yielded this:


Checking the dipstick it looks fine and the oil is the expected color. Truck hasn't moved in a while so everything should be settled. Can drain the oil tonight if needed.

Called the builder and he recommended to test the coolant for combustion so I will pick up one of those tests this evening. Otherwise he wasn't concerned but wasn't really expecting him to claim it either.

While of course I'd like it to be just leftover from the rebuild, new radiator, new hoses, etc, it doesn't give me that warm feeling.

*Edit for spelling

Forgot to add the photo of the reservoir showing the black (grey) stuff towards the top.
Couple inches of coolant in there now and if I recall correctly, gets half full when at operating temp.

The builder is right on!  

Unfortunately these engines like to crack between the exhaust seat and the spark plug.
But often they stay very tight and only let anything through after an extreme heat cycle.

My truck reservoir varys much more than that, and is nearly unreadable at this point.

Thanks Jim.

Don't interpret my comment as being unhappy with the builder - not at all. He came highly recommended and 460's are his cup of tea.

Going to be near HF tomorrow so may just wait and pickup a tester there.

I got to thinking about the layer in the bottom of the tank. Oil in coolant would always float, right? It's on the bottom of the tank but how would it get into the tank if it wasn't floating to the top in the radiator?

You didn't sound like you were angry at the builder at all.
If he knows these engines, he knows what goes wrong with them too!
And his advice is a first step.

Rubber in the coolant (from something like a water pump seal) can appear.

Plastics like polyethylene are especially oleophyllic. They latch on to oil and any part of the reservoir can be in contact over a bump, or when the radiator cap is releasing pressure.

I beat on my engine and it holds coolant but I have cracked enough heads to know that it can happen.

Scott, I would feel as you do in your situation. I'm glad the likes of Jim are here to make you feel at least a little better. Kudo's to you Jim!

BTW Jim, you may recall me asking about the wire in my alternator harness the other day? It is not my choke wire. I think you said it was the old stator wire which I'm inclined now to believe. Thanks!  

That wire goes three places on most charging systems.

1) The stator, obviously
2) The regulator (if external)
3) The choke (if it is a female bullet)

I have a hard time seeing details on my phone without my glasses, and I often don't bother to zoom in and just blurt out an answer.
I'll go back and look closer.

Yes - it is great to have a knowledgeable sounding board like we do here.

I remove and drained the reservoir into a mason jar. Was brown at first but overnight it all settled so is back to green with a layer of brown at the bottom. Honestly if the radiator wasn't new I'd probably assume a dirt dauber got into it. That's what it looks like. I've decided that since I have to replace the heater core anyways I am going to bypass it, and do a few flush cycles. If after that, I still have concerns I'll buy one of the testers we talked about.

I was looking at heater hoses although mine are new with the rebuild.
Seems like everyone is big on the Gates Green Stripe. Not cheap though and has a larger OD. Anyone have an opinion or do most just use whatever the parts counter gives you?

I have been using almost whatever hose I get.
But I try to shop at mom 'n' pop or commercial stores.
Used to be I would change heater hoses if I had to do the water pump, because it was buried behind my A.I.R. pump bracket.
I don't think I've looked at them since I got rid of that giant casting.

Scott, now that I see your edit, I think you simply have a bit of normal condensation in the muffler.
Did you test for hydrocarbons?

Hi, I am new on this site but I have a lot of experience with 429/460 engines. Looking at the picture of the stuff on your finger, I am wondering if it could be rust. Even after hot tanking, and /or shake and bake cleaning there can still be some rust in the block. These blocks are 40+ years old, I've seen the bottom parts of these blocks with solid rust in them. Even after cleaning, there is no guarantee that ALL of the rust or scale is completely gone.

If the smoke you see from the exhaust is from coolant, then you should notice a sweet smell to it, as well as a loss of coolant. You could also pull the spark plugs and see how they look, also, if you detect anything from looking at your plugs a compression and a leak down test could be next.

I like to start with easiest and least expensive tests first, a cooling system pressure check with the engine cold, and again with the engine hot. The hydrocarbon check is also a good check but if coolant is getting into the combustion chamber, you still need to know where the problem is, the spark plugs should tell a story.

I hope this helps,

Thanks Staci.
I think it is just rust. The mason jar has been sitting for a couple days and everything brown is at the bottom and the top is nice and green.

I ordered some cleaner so once I get all my wiring changes buttoned up, I'll do a few flush cycles.
Will check the plugs during that process as well.

I am glad to hear that. The last thing anyone wants is a problem with a new engine.