Recent 340 Rebuilt - Coolant creating thick green film

[Titan1969]

I recently took possession of a long term resto project and was excited to finish up a few small items.....until I opened rad cap and saw thick green film on top of coolant. The 1973 340 was rebuilt by a reputable shop but not dyno'd just installed and broke in, prior to me taking possession. The rad is new also.

So you might say "bring it back to the shop". Well resto work done in MI and car was shipped to me in CA day after Xmas...so not so easy to solve with the shop.

Pics attached.

I have drained and refilled the coolant but the issues persists and I can like skim the thick layer off the coolant with a paper towel, so the rad fluid is separating from the film.

I checked dip stick for both trans and oil, no signs of coolant ( thank goodness).
Tsat opens, car runs normal temp and idles ok, car doesnt smoke.

Only item not replaced when the car was restored was the heater core, I would think if heater core was contaminated I would solved by now by draining and refilling.

at first I hoped it was a case of the rebuild shop not cleaning out the coolant passages, but no way to verify this.
Could the cleaning soluiton for the line hoing etc, create this thick film if not cleaned out prior to running the motor?

Since I dont have a "real" coolant flush system, would it make sense to bring to shop and have it professionally flushed? or am I wasting my time? is it more likely a head gasket?

Thanks in advance for any thoughts on next steps here, really a bummer paid a fortune for the car resto work and cant even drive it.

any links for my issue are appreciated

 

[Adam]

Looks like there could be oil getting in there. I would drain all the antifreeze coolant out, flush it with clear water, fill it with clear water, and then see what the slime looks like after it has run for awhile.

There are places that analyze engine oil for contaminants, maybe they can analyze the green goop.

 

[fasjac]

Like Adam said, flush repeatedly with water.
may even connect directly to the heater core and flush too.
I would also pressure test the cooling system, just to know if it’s holding. It sure looks like oil may be in there?? A clear oil dip stick is good though. BG makes a really good chemical flush. Good luck sir and let us know what you find.

 

[704406]

You don't say if the car is auto or manual trans. Follow the suggestions and flush the system. In your first picture it doesn't look like an original rad, I once had a trans cooler in the bottom of the rad leak trans fluid into the rad, so check the trans fluid level if yours is an auto trans.
It might be best to pull the rad and get it flushed at a rad shop. They can test the trans cooler as well if it's got one.

 

[moparleo]

Draining and refilling does nothing in your case. Definite fluid transfer happening. Pull the sparkplugs to check for gasket problems. Do not run the engine any more as anything that does get into the oil pan will be pumped to the bearings. You may end up pulling the engine to completely clean it inside and out. Remove the valve covers as well to get a look inside. If you see the same thing, time to pull it out...

 

[Titan1969]

Draining and refilling does nothing in your case. Definite fluid transfer happening. Pull the sparkplugs to check for gasket problems. Do not run the engine any more as anything that does get into the oil pan will be pumped to the bearings. You may end up pulling the engine to completely clean it inside and out. Remove the valve covers as well to get a look inside. If you see the same thing, time to pull it out...

OK was guessing it would end up this way. hindsight I shouldve just bought a crate motor, but wanted to keep numbers matching for the resto. Ill report back with pics after valve cover removal. thx everyone

 

[Adam]

He said there is no sign of coolant in the oil. I think he can safely explore some possible causes. Draining and running water may tell him if the problem is oil or trans fluid from radiator cooler, etc. Also, he may not need to pull the engine it may be a cracked head, (high pressure oil forcing its way into a water jacket) or a head bolt not torqued properly, crud in the bottom of the threads, etc.. if the block has a hairline crack, well he’s really not hurting it anyway.

 

[budascuda]

OK was guessing it would end up this way. hindsight I shouldve just bought a crate motor, but wanted to keep numbers matching for the resto. Ill report back with pics after valve cover removal. thx everyone

You did the right thing by keeping it a number matching car.
The best of luck to you, I am certain you and the folks here will figure it out.

 

[Titan1969]

He said there is no sign of coolant in the oil. I think he can safely explore some possible causes. Draining and running water may tell him if the problem is oil or trans fluid from radiator cooler, etc. Also, he may not need to pull the engine it may be a cracked head, (high pressure oil forcing its way into a water jacket) or a head bolt not torqued properly, crud in the bottom of the threads, etc.. if the block has a hairline crack, well he’s really not hurting it anyway.

yes ill explore a few more options before throwing in the towel and pulling engine, what can it hurt at this point. I spoke to another mopar ASE mechanic today, he "thinks" the 340 oil passage from the bottom end, is very near the coolant passages that lead up to the rocker arms. If the gasket ( or head issue ) is occurring on the top end, he said the high pressure oil / gasket head area could very well be pushing into the coolant passage. This would leave no coolent on the dip stick / bottom end but still be enough oil pressure present to over come the coolants pressure. So something else for me to investigate.

Im getting an ASE mechanic to drop by the car next, do a visual insepction and give me a quick write up of whats hes observed before I tear into it. Since Im in CA, we can never have enough paperwork and experts in case I need to fight the motor shop for some reimbursement. hope it doesnt come to this.

 

[704406]

I don't think I'd pull the motor and disassemble it until there was contamination in the oil. Follow the suggestions and try to eliminate 1 thing at a time.
I'm sure you'll kick yourself if you pull the motor if you didn't have to, if it turns out it's a relatively simple fix.
Let us know if there is green goo inside after you pull the valve covers.
Is it standard or auto trans?

 

[Titan1969]

I don't think I'd pull the motor and disassemble it until there was contamination in the oil. Follow the suggestions and try to eliminate 1 thing at a time.
I'm sure you'll kick yourself if you pull the motor if you didn't have to, if it turns out it's a relatively simple fix.
Let us know if there is green goo inside after you pull the valve covers.
Is it standard or auto trans?

Auto 727 and has a brand new rad. So theres a chance, i suppose, that the rad is defective also. Easier to pulll it and have it tested, so I can eliminate it.

 

[Titan1969]

pics of car, sure looks good...despite not mobile

 

[budascuda]

yes ill explore a few more options before throwing in the towel and pulling engine, what can it hurt at this point. I spoke to another mopar ASE mechanic today, he "thinks" the 340 oil passage from the bottom end, is very near the coolant passages that lead up to the rocker arms. If the gasket ( or head issue ) is occurring on the top end, he said the high pressure oil / gasket head area could very well be pushing into the coolant passage. This would leave no coolent on the dip stick / bottom end but still be enough oil pressure present to over come the coolants pressure. So something else for me to investigate.

Im getting an ASE mechanic to drop by the car next, do a visual insepction and give me a quick write up of whats hes observed before I tear into it. Since Im in CA, we can never have enough paperwork and experts in case I need to fight the motor shop for some reimbursement. hope it doesnt come to this.

That sounds reasonable, whether thats the case or not. definitely worth checking.
But i f you don't mind, I will ad my two cents too.
One thing obvious from your pictures is that the fluid in the rad looks "frothed up", like the way specialty coffee is made, the theory of " close" passages+high pressure oil+latte` like foam on top.........the problem might not be a catastrophic thing after all!, I hope

 

[budascuda]

pics of car, sure looks good...despite not mobile

View attachment 78540

View attachment 78541

Looks fantastic! Stay patient!

 

[Titan1969]

Dipstick. Engine has approx 4 hours run time. Seems clean and normal. Opened valve cover openings peeked inside, nothing foamy or green. Can see rockers with oiled pooled, oil normal.

 

[budascuda]

I just thought of something, is it possible to at least call the rebuilder and ask him if he usually pressure tests block+heads before hand?

 

[70chall440]

I would thoroughly flush it, refill it with water and run it for awhile and see if you get any more contamination. If its a head gasket issue, cracked head or block issue it will come back but usually if oil can get in to the cooling system then coolant can get into the engine (usually). That said, on an initial rebuild it is possible that somehow oil got into the cooling system by accident and it is nothing more.

You dont have anything to lose by trying everything first before diving into it deeper.

 

[budascuda]

Since the oil is not contaminated, it might not be oil/coolant problem, it could be exhsust/coolant problem.

If there was a hairline crack(very small one) in on of the heads, between an exhaust and coolant chamber wall, hot exhaust could find its way into the coolant side (and froth it up) but not the other way around.
I have come across this problem with Mazda 2600, the chamber walls in the aluminum head are too thin and if the engine overheats just once, the membrane thin chamber walls in the head will crack upon cooling.

 

[Mopar Nut]

Have you pressure tested the coolant system?

 

[Titan1969]

Have you pressure tested the coolant system?

no, havent driven the car anywhere due to the coolant issue. I could find a local shop to test.