QuestionLast March my wife and I took the plunge and bought our 1st muscle car, a 1970 Mercury Cougar. It has the 351 Cleveland 4V engine with the Hurst close ratio 4 speed tranny.
We checked it out first as best to our knowledge but apparently we were too excited and forgot to check the basics, like the fluids.
We didn't have any trouble with the operation of the Cougar, either performance or operating temps and pressures. It was just me checking the antifreeze one day when I noticed what I later found out to be oil. I quickly checked the dipstick and was relieved to see no milky residue and no oil consumption.
The next day I did my own flush and fill without using a flushing chemical, just running water through the cooling system. I refilled it and closed it up. A few weeks later, after daily checking the antifreeze, the oil showed up again. I had my local shop, which I trust BTW, do a complete flush and fill, chemicals and all, and to verify that what I was seeing was truly oil. It was and afterward the antifreeze was nice and clear. The shop manager mentioned that if the oil returned I was looking at a costly repair.
Fast forward 7 months. No oil showed up in the weekly, not daily, driving of the Cougar. I think the longest drive I had in the 7 months was maybe 60 miles.
Now, I have returned from a 1200 mile trip and have found the oil back in the radiator AND a quart low on the dip stick. I belong to a Cougar forum and have asked about this problem. Nearly everyone said "head gasket" but one person mentioned something about a "water jacket" being cracked.
The history of the motor is unknown except for what we were told at the dealership: Engine rebuilt 3000 miles earlier, approximately 100k on the motor before rebuild.
I have scoured the internet looking for answers to the "oil in coolant" question. All I see is head gasket this, head gasket that. I have even seen that a blown HG would have symptoms the other way: coolant in the oil. The oil is fine.
My question here is: What ways could the oil mix with the coolant and if you know, how common is this "cracked water jacket" problem? It was mentioned that this has appeared on a few 351 motors.
Thanks in advance!
Paul
AnswerThere are several ways to uncover the problem. One is use a carbon monoxide detector on the radiator. most radiator shops have such a device. It will usually pick up a head gasket leak. If I were doing the job I would use a dye in the engine oil that will glow under a black light. The flush the radiator and drive the car until the oil shows up in the radiator. Check the dye. Experience tells me that there is a slight leak in one of the head gaskets and engine oil under 40 pounds of pressure is leaking into the coolant. As the cooling system runs at 15 pounds of pressure it could answer why there is no coolant in the oil.
Brad
