Recently purchased a 1968 Cutlass Sport. PO had the engine rebuilt about a year ago. He was and older gentleman and didn’t thrash it or drive it much.

After purchasing and fixing some minor electrical issues, I noticed a small pool of coolant at the intake manifold driver side. It was a bright green. I figured no big deal and made sure they were torqued down properly. Some bolts were a little loose. Got rid of the leak for a little bit.

After a few cruises the leak came back but now it looks dark like oil. Pooling at the same place the coolant was. Not sure what’s going on underneath and posting hear to get some ideas of whats going on.

Ive searched and haven’t come across something like this. It was coolant, now looks like oil. I recently changed the oil prior to this and it still looks good, before the change the old oil came out dark, nothing abnormal.

 

If the engine is running fine, no knocking, no banging, no tapping, not losing oil, not dripping copious amounts of oil & as you noted some of the intake manifold bolts were loose - I'd remove the intake manifold bolts one at a time (individually one at a time - not all at once). If the oil (during an oil change) isn't milky looking you most likely have a loosened manifold intake. Clean each bolt hole and each bolt as best you possibly can so the hole and bolt are as dry as possible, take some black RTV and lightly apply a film to each bolt - just enough to cover the threads, install each bolt back into the hole one at a time until you've done this with all bolts. Snug all bolts down, then torque all the bolts as outlined in the CSM. Keep a watchful eye on seepage. Since you stated a number of the bolts were already loose which you had to torque, there's a good chance the intake manifold simply raised above the level of the RTV used when a P.O. did the gasket installation however long ago that was - evidently long enough ago to find loose bolts that required torquing.

 

This seems like an issue of the bolts being loose not fluids wicking up the threads. Putting sealer on the bolts won't solve this. Try tightening the manifold bolts a bit more.

 

I would clean it off real good with some brake clean and clean rags. Then go to the parts store and buy a bottle of the die they sell for detecting leaks. If you dont have an Ultraviolet flashlight just buy the whole kit that comes with the die and the light. Put the die in the oil and drive it for a while. The use the light to see where the leak is.

I am betting it is leaking around the front somewhere and getting blown back by the fan.

 

What bill said. The front rail seal if rubber has a good chance of being out of place, if RTV it has a chance of being improperly formed. Either of these will lead to a leak. I would also double check the valve cover fasteners, they should be eventl slightly snug not torqed down tight.

 

Thanks everyone for the input. I’ll try torquing them down again and get a dye kit. The PO or mechanic used the plastic gaskets at the front and back, it looks sealed pretty well but who knows.

Question: Should I back off the bolts a bit and then torque down? Back them all off and follow the sequence? No leaks on the passenger side.

 

The problem with using the front and rear seals is mostly that they don't compress enough not allowing the side seal to seal with an aftermarket manifold. Aluminum manifold manufacturers suggest to throw them away and use a bead of RTV in their place.

 

From what I understand regarding your statements, thus far, it sounds like your engine is healthy and not spewing oil with significant oil loss &/or milky white oil in the oil pan; albeit, just leaking on evidently the left-hand driver side intake manifold. With that said, personally I'd back all of them off (very sparingly) in reverse sequence as prescribed in torque sequence defined in the CSM, then I'd torque them in their proper sequence as prescribed in the torque sequence defined in the CSM. There is "some" (very minor), but some minor flex in any intake manifold when you are applying torque (left>right; right>left; front>back; back>front). The gasket & any sealant has already "formed" into position. I think you just need a good old-fashioned snugging up of the bolts into their threads. I'll mention this. You know most people are dead set in suggesting bolts don't wear out - but, they do. Additionally, the threads wear out just like any threaded container holding a bolt - that's just a fact. The more times some PO removed those bolts, and reinserted those bolts the greater the loss of solid adhesion of the bolt to the threads. I don't believe anyone knows with any degree of certainty (1) if they're the original OEM bolts, (2) improperly sized bolts, (3) wear characteristics of the threads/bolts, etc.; and, (4) how many times the bolts have been removed and re-tightened in the past. The engine is 50+ years old - no one knows the prior history of this engine. Do your best to tighten them all up and monitor the situation. I'm nearly positive others will have differing suggestions. To each their own.

 

Thanks everyone again. I backed the bolts off slightly in reverse sequence and noticed 1 washer missing and another severely cupped. I replaced both, unfortunately I couldn’t find the thick washers at the hardware store so I used the thickest they had. Torqued per CSM at 15# then again at #35. Seems to have fixed the leak. Cruised around, hit the freeway and nothing so far. But now my idle is sticking a bit and I have to tap the gas to get the revs to come down, so on to the next!