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Coolant in oil. Need help identifying cause.

3141 Views 84 Replies 14 Participants Last post by  eric32
This is sort of related to my other post regarding a cam swap. In the process of learning more about that process, it was discovered that the dumped oil contains a good amount of coolant. The results of the oil test can be found here. Suffice it to say, there is coolant in the oil. So I am now taking a detour on my way to a different cam as this issue will have to be addressed first.

I am looking for help identifying where the coolant may be seeping into the oil. I will do a pressure test tomorrow, but for now I have pulled the spark plugs out and stuck an endoscope into all the cylinders. The results are below. Note that the truck has not been driven or started in about 3 days prior to my doing this work.
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Here are some picture from the endoscope. All pistons look about the same - pretty carboned up. Some, however, have what appears to be moisture. Can you guy draw any conclusions?

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Whichever cylinder the clean spark plug came out of is probably the cylinder taking coolant. Note the borescope photo of that cylinder is one of the missing from your collection.

You're likely referring to spark number 5. Here are a few shots of cylinder 5. Looks about the same as all the others so far as I can see.
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Whichever cylinder corresponds to the plug you have marked #5 is the cylinder eating coolant.
Spark plug porcelain is steam cleaned to practically new.

Now you've got to find out why and where the coolant is coming from.
The plugs are numbered in accordance with the cylinder numbers.

"Now you've got to find out why and where the coolant is coming from." - Do you think pulling the head will answer that vexing question?
Well, did the coolant pressure test. Cranked it up top 16 PSI and left it there for about 25 minutes. There was some inconsequential loss in pressure to, perhaps, 15.5 PSI. I mean that could just be be leaking around the cap or I noticed a tiny leak here, which might account for that small variation:
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But that in my opinion isn't enough to account for the amount of coolant I lose when I drive it (for less than 25 minutes too). There sure as hell wasn't any coolant dripping into cylinder number 5 (or any other cylinder for that matter) - I looked inside it from every angle.

I guess the leak down test on 5 is next.
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You might not see any leak until the engine is hot and running.
The piston pumping action will pull it into the chamber.
If the engine is hot, then the cooling system is already under pressure, which, I guess, renders that pressure tester pump pretty much useless.
Operating is different from not, the heat and the load dynamics can and do open these wounds
This rationale suggests that if I do a leak down test on that cylinder, it will ALSO need to be performed at operating temp. I am already imagining trying to find TDC on #5 and then plugging the tester finagling around the scalding block and headers. Seems like it would be easier to just pull the damn head off and just look for any sign of trouble.
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I must admit that I kind of like your succinct conclusions.
There is no doubt at this point that I will be tearing into this engine in short order. But I did notice another oddity and wanted to ask yall about it. Check out this gap between the intake manifold and intake port on cylinder 1. And yes, that's a feeler gauge on the second picture buried in there. It's a 0.015 gap. Wouldn't this create a big vacuum leak? At least for cylinder one?
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At which point the rest was slapped together by someone who really didn't know completely how to do it..
He takes it home and puts the big heads and small intake on, doesn't check fits, slaps that Thumpr in there, bolts on all his bling and fires it up.

Are you feeling the same vibe?
Yeah.... That makes some sense. The invoice doesn't mention the heads or the intake at all.

And indeed, if the intake doesn't quite line up with the holes on the heads, why wouldn't it leak coolant?

I suppose the jury is still out on whether I will keep the heads when tear into it, but even if I get aluminum ones as replacement, I imagine they will still be of the "taller ports" variety. Isn't that some performance feature? So... stands to reason I will need a new intake one way or the other. So what do you recommend?
Are you indicating that the gasket and the intake don’t cover the port roof? If so that is an air leak.

Yeah, was my question: "Wouldn't this create a big vacuum leak?" And you just answered it. But also my thought was if the intake ports don't line up, what are the chances that the coolant passage ports between the intake and heads line up?
A big vacuum leak the car wouldn't idle. My last response, you're getting so many suggestions you don't know which direction to go.
Good Luck
Happy Motoring
The direction is rather clear. This weekend I will pull the intake off and then play it by ear from there. If the source of the coolant leak is inconclusive, the heads will come off. The ultimate goal here is to recam the engine and I will get it done even if I have to rip the motor out and take it to a machine shop.

I would, however, like some recommendations as to what intake to use to cover up those head ports. Cuz clearly, as Eric pointed out, my current intake isn't tall enough for those heads.
Josh , I had the same manifold/ head dilemma when I put together the motor for my T . brodix IK 200 heads , older edelbrock street tunnel ram . I think there's at least 4 different intake gasket sizes ,. I ended up with a medium port size that had enough material to come to the top edge of the port & still cover the floor of the opening . Its been awhile , but I had to trim the gasket slightly where it rests on the China walls in order to maximize coverage @ the ports. Its been on now for a number of years without trouble , but it took time measuring ,getting the right gasket ,& also getting proper alignment . the 400 blocks are notorious for leaking between cylinders. Especially 3&5 - 4&6 . I have a machinists gauge block that's large enough to check the deck . We had trouble with the 400 blocks in 1968-72 @ the Chevy garage , the fel- pro composition head gaskets generally work well .
Great info. Thanks. I have discovered another gap between the intake and an intake port. This one is for intake port of cylinder 5 and it's a gap of of about 0.025. No clue how somebody could have done such a slapdash job putting it on. I'm afraid my current intake will have to go. Eric has made some nice recommendations as to a potential replacement. I would like to still go with a dual plane intake. What I will also do is call Dart Machinery (heads manufacturer) tomorrow and see if they have any dual plane intake recommendations for the heads as well.

By the way, are you referring to these Fel-Pro gaskets:
So let’s chase this a little further.

Vacuum leaks typically cause a fast idle with little control from resetting the curb idle and don’t do well with reducing fuel flow from the idle mixture screws.

Generally manifold vacuum is down.

Number 5 could be dried fried, but usually an air leak in one place is felt everywhere.

Fitment, not going to go back and hunt for your other inputs, so how about going back over what heads and whether they were milled, ported, etc. What intake and gasket set if known? Whether the block has been decked?

I will do my best to find out, Bogie.
If I may ask another dumb question here. I was under the impression that it was coolant that flowed through the tranny cooling lines (It's TH350). However, after unthreading those flare nuts, I see ATF dripping out. Is ATF flowing through the rad?
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I noticed that when the rad is under pressure, there is a small leak of coolant right here:
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So it's not where the flare nut from the ATF line threads on, but rather around the base of the biggen nut that, assume, threads into the rad body. That seems mighty close to the where the ATF is. How do I check if that ATF container inside isn't letting in coolant?
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Am I crazy or is my harmonic balancer puller not designed for this specific harmonic balancer?
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It would appear I need this tool instead right?
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The new cam has some kind of powder coating on the lobes in sharp contrast to the picture on the box. Also I don't think I have ever seen black cam lobes on a cam pulled from an engine on YouTube. Shouldn't they be polished? Is this something to be concerned about?
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Had to shut her down for the night, but started removing the intake and couldn't help noticing a preponderance of some weird debris inside the bolts holes that go around the coolant passage ports:
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What the heck is that? The other bolts deeper afield don't have this issue. Is this rust or what? Looks like dirt. I actually had to stop and vacuum a bunch of it up so as no to drop it in later when I take the intake off.
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Those bolt holes on the 2 ends of each head go through the head and into coolant. I'm not speaking about exactly what the material is, but obviously for whatever reason there is a leak that deposited the material. It's good form to use liquid teflon sealer on the (cleaned) threads of any bolt that goes into the coolant (usually just do all intake and head bolts with sealer so torque is even). Wire brush the bolt threads and chase the threads in the bolt hole (removes any old sealer as well as junk).
Why not just use a standard teflon tape? Doesn't it accomplish the same thing without crumbling all over the place?
Well, gentlemen, I don't see any evidence of a coolant leak here:

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It seems I am stuck on the horns of a dilemma. Pull the heads or not. My gut is telling me that pulling the heads WILL NOT reveal anything obvious. It's likely going to be a bunch of work for very little result. I will probably just end up changing the head gaskets and hope for the best. I do think that if there was an actual head gasket rupture, the pressure test would have revealed it.

There is something else I noticed though. Based on this doc, the head bolts have to be torqued to 70 ft/lb. I tested a few bolts in the middle of both heads and they were not even close to 70 fb/lb. I'm really tempted to just retorque the head bolts, add some K-Seal to the coolant and cross my fingers. Well, and, obviously swap the cam, cuz that's why I'm digging in there in the first place. What do yall think?
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