Coolant in oil after intake manifold swap

[Fishfan]

Hi guys, I just completed an intake manifold swap on my 66 Polara with a 318 Poly. The purpose was to go from a 2-BBL to a 4-BBL carb. I just ran the engine to tune the carburetor and checked the oil afterwards. The oil was brown and tasted of coolant. I have some questions, but first a little more background.

1. Before removing the old manifold, I took off the water pump (to replace it). Rad was drained too.

2. The intake manifolds (both the old and the new) have one set of what I presume to be water passages blocked (see picture).

3. When I put the new gaskets on I followed directions to put plenty of sealant around the ACTIVE water passages (on both the block and the manifold.

4. I did not put any sealant around the BLOCKED water passages.

5. When I reassembled everything, I had a huge water leak from water pump. I had to remove water pump again clean both surfaces, put a new gasket on and put plenty of sealant as dressing on both the timing cover and the water pump. I had no leaks afterwards.

So here's the questions:

Could the source of the coolant in the oil be contamination from when I removed the intake manifold? I didn't see any coolant when I removed it (remember I had removed water pump and drained rad).

Obviously water doesn't flow down the blocked passages on the manifold into the heads but now it occurs to me that water circulating around the heads might flow UP to the blocked manifold passages (with some pressure). Could the fact that I didn't put sealer around the blocked passages mean that water is leaking there?

My plan is to change the oil and filter tomorrow. Hoping I didn't do any damage and hoping it was just some contamination from manifold removal.

Photo of old 2-Barrel intake manifold. The "new" one also has these rear water passages blocked.

 

[1970FuryConv]

Hi guys, I just completed an intake manifold swap on my 66 Polara with a 318 Poly. The purpose was to go from a 2-BBL to a 4-BBL carb. I just ran the engine to tune the carburetor and checked the oil afterwards. The oil was brown and tasted of coolant. I have some questions, but first a little more background.

1. Before removing the old manifold, I took off the water pump (to replace it). Rad was drained too.

2. The intake manifolds (both the old and the new) have one set of what I presume to be water passages blocked (see picture).

3. When I put the new gaskets on I followed directions to put plenty of sealant around the ACTIVE water passages (on both the block and the manifold.

4. I did not put any sealant around the BLOCKED water passages.

5. When I reassembled everything, I had a huge water leak from water pump. I had to remove water pump again clean both surfaces, put a new gasket on and put plenty of sealant as dressing on both the timing cover and the water pump. I had no leaks afterwards.

So here's the questions:

Could the source of the coolant in the oil be contamination from when I removed the intake manifold? I didn't see any coolant when I removed it (remember I had removed water pump and drained rad).

Obviously water doesn't flow down the blocked passages on the manifold into the block but now it occurs to me that water circulating around the block might flow UP to the blocked manifold passages (with some pressure). Could the fact that I didn't put sealer around the blocked passages mean that water is leaking there?

My plan is to change the oil and filter tomorrow. Hoping I didn't do any damage and hoping it was just some contamination from manifold removal.

Photo of old 2-Barrel intake manifold. The "new" one also has these rear water passages blocked.
View attachment 560682

Coolant water mixture from the heads still contacts the blocked passage, so yes, it should have been sealed both sides.

Pressure tester on radiator and quiet garage may give you a hiss at the area of the leak, once you pump the cooling system up to 15 psi.

 

[57fury440]

Is the 4 barrel manifold a new aluminum one or a factory cast iron one? I had a few poly 318s and I don't recall using anything but new gaskets. I know that on LA318s the exhaust manifold bolts go into the water passages, and you have to put sealant on the bolt threads to seal them. You said you had to redo the water pump because the surfacers were not clean enough. Maybe the same goes for the manifold.

 

[Fishfan]

Is the 4 barrel manifold a new aluminum one or a factory cast iron one? I had a few poly 318s and I don't recall using anything but new gaskets. I know that on LA318s the exhaust manifold bolts go into the water passages, and you have to put sealant on the bolt threads to seal them. You said you had to redo the water pump because the surfacers were not clean enough. Maybe the same goes for the manifold.

Old cast iron manifold. I put new gaskets in.

 

[Fishfan]

Coolant water mixture from the heads still contacts the blocked passage, so yes, it should have been sealed both sides.

Pressure tester on radiator and quiet garage may give you a hiss at the area of the leak, once you pump the cooling system up to 15 psi.

Ugh. That's what I was afraid of.

 

[Fishfan]

Coolant water mixture from the heads still contacts the blocked passage, so yes, it should have been sealed both sides.

Pressure tester on radiator and quiet garage may give you a hiss at the area of the leak, once you pump the cooling system up to 15 psi.

Wouldn't the combustion be compromised if water was escaping through the unsealed gasket on the blocked passages?

 

[1970FuryConv]

Wouldn't the combustion be compromised if water was escaping through the unsealed gasket on the blocked passages?

Not necessarily. It might be vaporized and sent out the exhaust pipe.

Also, gravity might dictate that coolant/water is draining onto the intake valley and down into the oil pan.

If the oil did not have coolant in it before the intake was replaced and it does now, the intake replace is probably the culprit.

Further, sealing the intake bolts if it's a small block is a good idea.

 

[Fishfan]

Not necessarily. It might be vaporized and sent out the exhaust pipe.

Also, gravity might dictate that coolant/water is draining onto the intake valley and down into the oil pan.

If the oil did not have coolant in it before the intake was replaced and it does now, the intake replace is probably the culprit.

Further, sealing the intake bolts if it's a small block is a good idea.

I guess the low friction thing to do would be to change the oil and filter and see what happens, understanding that I probably have to remove and reinstall the manifold. FACK.

 

[mrfury68]

After replacing the intake manifold did you change the oil and filter? That's always the last thing I do before firing up the engine. After a few hours of running, drain the oil and change the filter again. Changing intakes can get anti-freeze everywhere, including in the crankcase. I also agree with some RTV silicone on water passage bolts. Good luck.

 

[413]

What kind of sealer did you use? Did you put it together immediately, or let it set up first?

You should have sealed up those blocked passages, there is still coolant there amd the gasket is what seals it.

Maybe the manifold is cracked? Or been milled down? It is about 60 years old. Did you install the manifold dry and see if it fit on the heads correctly?

Do you have metal intake gaskets? Did you use the end seals or just silicone there. The seals could be keepimg the intake from going down enought to seal if anything is milled.

Does the car start, run, and idle as good as before, meaning there are no vacuum leaks?

 

[detmatt]

I’ve never worked on a poly, water passages in the intake??

 

[413]

T stat is on the intake, along with bypass hose, heater hose bibs and temp sender. You know, just like an LA engine arrangement.

here is a pic of the gasket. 4 intake ports, 2 water ports, one exh crossover On each side.

 

[Fishfan]

What kind of sealer did you use? Did you put it together immediately, or let it set up first?

You should have sealed up those blocked passages, there is still coolant there amd the gasket is what seals it.

Maybe the manifold is cracked? Or been milled down? It is about 60 years old. Did you install the manifold dry and see if it fit on the heads correctly?

Do you have metal intake gaskets? Did you use the end seals or just silicone there. The seals could be keepimg the intake from going down enought to seal if anything is milled.

Does the car start, run, and idle as good as before, meaning there are no vacuum leaks?

I used the sealer that came with the felpro gasket set you posted the picture for. I used the end seals that came with the kit.

Yeah, I realize now that I should have sealed the blocked passages. My flawed logic was that if they were blocked there would be no water passing through them. But I didn't think about water circulating in the heads coming UP to those blocked passages.

I test fit the manifold an all seemed OK. Holes lined up.

Engine runs better than at any time in the 18 years I've owned the car. Of course, a brand new Edelbrock 4-bbl compared to a 2-bbl stromberg that's been rebuilt 20 times is no comparison and I only drove it a mile or two.

 

[Fishfan]

T stat is on the intake, along with bypass hose, heater hose bibs and temp sender. You know, just like an LA engine arrangement.

here is a pic of the gasket. 4 intake ports, 2 water ports, one exh crossover On each side.

View attachment 560722

Yeah, this is the set I bought from Summit. This is how I installed them. Ok. So obviously, I need to re-do the work. I've made peace with that. Question is have I damaged anything? What to do after I install new gaskets? Change oil several times?

 

[1970FuryConv]

Yeah, this is the set I bought from Summit. This is how I installed them. Ok. So obviously, I need to re-do the work. I've made peace with that. Question is have I damaged anything? What to do after I install new gaskets? Change oil several times?

View attachment 560733

I think if you damaged something, the engine would not run so well.

I would reinstall the intake, change the oil, see if you still taste/smell coolant. If not, you're probably good to go. You can keep checking the oil to be sure. Also, a cooling system pressure test that shows no leak is a big relief for a mind that's been dealing with the same problem for a long time.

 

[fury fan]

I’ve never worked on a poly, water passages in the intake??

Yes, smallblocks and Magnums flow coolant thru the intake, that's where the T-stat housing is located.

We're spoiled by the bigblock's design. Simple intake manifold changes with no coolant system involved.

And I've never had a BB block the heat riser passage in the intake. I've had 2 smallblocks, and each of them did it twice in several years.

 

[Fishfan]

I think if you damaged something, the engine would not run so well.

I would reinstall the intake, change the oil, see if you still taste/smell coolant. If not, you're probably good to go. You can keep checking the oil to be sure. Also, a cooling system pressure test that shows no leak is a big relief for a mind that's been dealing with the same problem for a long time.

I reinstalled the intake and have changed the oil twice. Good to go.