Packard Forum Index » V-8 (1955-56)

I am looking for some advice in diagnosing a problem with my '56 400. I just returned from a Blue Ridge Packard tour and heard a hissing noise from under the hood. When I opened the hood I saw what looked like chocolat milk bubbling out from around my radiator cap and a puddle under the car from the overflow vent.

The car ran absolutely perfectly on the tour with no overheating problems at all. I checked the oil and, while it was at the low mark on the dipstick, it looked normal. I checked the transmission fluid and it doesn't register on the dipstick although Bob Aller rebuilt ransmission shifted perfectly during the tour.

So, I'm thinking I have a leak in the transmission cooler allowing the tranny fluid to get into the coolant system. I'm also wondering what the "chocolat milk" mixture will do for my cooling system and if I can flush it all out. And I'm also wondering if I have that same mixture in my transmission and what it could do in there. Nothing registered on the dipstick which could be a good thing (no chocolat milk).

Any thoughts or advice on what to do next?

I think I would drain a bit of trans fluid to see the condition. If water or chocolate there, it should be on the bottom and come out first. If present then change but if not then just add. It is suspicious that there is nothing showing on the dipstick. At any rate, go ahead with the coolant flush. Doubt any damage would have been done to the cooling system. Finding a NOS cooler at a decent price may be an adventure but many have recommended going to an aftermarket air cooled unit anyway so that might be one option.

99.999% chance that you are right about the transmission cooler being the culprit. I would be most concerned about water that backed up into the tranny once the trans. pressure fell below the cooling pressure when the car was shut off. Perhaps dropping the tranny pan is in order.

I would assume a good flushing of the radiator / cooling system would get most of the oil froth out of the cooling system. Maybe a detergent or similar remedy will be recommended by others here.

Last and certainly least of your problems at this moment is that if you were frothing around the radiator cap, the cap is bad and needs replaced.

Many more will be along soon with great advice.

Have you checked the motor oil also just to make sure you don't have an engine crack/head gasket somewhere that is leaking oil in the coolant.

Normally, there is no direct engine oil pressure in contact with the cooling system except in the earlier 3 piece engines equipped with oil system heat exchangers. I would be highly suspicious of one of those letting go, especially since the newest one is now 71 years old.

That said, Kev has a good point on possible head gasket. There could be some oil pushed in, and would also help explain bubbling from the radiator cap possibly caused by combustion pressure. I still vote for tranny cooler, very failure prone and seems to fit the symptoms.

Let us know what you find.
Jim

I still vote for tranny cooler, very failure prone and seems to fit the symptoms.

At least in my own experience and that of other local owners, the transmission cooler is not failure-prone, quite the opposite. But I do agree it would be my #1 candidate for your symptoms.

Have you checked your transmission and oil dipsticks? If either of them is full of chocolate milk there is your answer, either a bad tranny cooler or blown head gasket.

Thanks everyone for the advice, it's appreciated. Kev, I did check the oil and it looked normal. I don't know if that means I don't have a blown gasket or not. I'll replace the tranny cooler and see if that solves the problem. Max Merrit has them for $225. I'll post the results when I get it done.

Jed, perhaps a better move would be to remove the cooler and pressure check. A local radiator shop could do this for you if need be. In my personal experience with many verities of application from heat exchangers in automobile radiators to industrial heat exchangers in fire engines and commercial applications such as over the road diesel engines have been that the heat exchanger are a weak link, periodically exchanging fluid into fluid.

From what Dave (O_D) has said, this is not the case on Packard V-8 applications. I stand corrected and would strongly recommend before spending the money and not being sure of the true issue, test yours.

Best of luck,
Jim

Just to point out that red tran fluid into the coolant would not make brown, would it? I've also never seen a bad cooler (other than the necks rusted off) in 19 years of Packard service. The actual exchanger is stainless on these cars. I'd definitely drop a sample of engine oil and tranny fluid just to check.