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Coolant in oil. Need help identifying cause.

3141 Views 84 Replies 14 Participants Last post by  eric32
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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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Start it up (if you can) and spray a small of carb cleaner on it. Key word, SMALL.
Yes, that would be a vacuum leak.
More evidence your coolant loss could all be from the intake gasket after all...

You may need the double thickness intake gasket to get that intake to seal up, it's basically your only hope with that intake and head combination.
Problem is the basic aluminum EPS intake is made for the smaller, shorter stock port opening rather than the wider and taller port on those Dart 215cc heads.
You run into the same problem with a lot of older vintage aftermarket Hi-Po intake manifolds that were designed for stock headport size and fit. They won't cover and seal along the top of the bigger modern port roof.

You are probably going to need a different intake manifold, I don't think the .125" thick intake gaskets are going to do the trick and raise the intake enough to get it to seal up. I've never tried it with that big a gap.


Reading back through your initial post on this engine and the machine shop invoice..... From the way the invoice is worded and the evidence your finding.....it looks to me like they rebuilt and assembled a 400 short block, then customer picks it up and finishes it ....
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?
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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?
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?
trust me, all the holes line up. Leak from a water passage into the cyl might be the culprit. My 31' has an old 350. figure around 1978. it has 6089 performer heads and an old Weiand intake, no leaks, there will be after I said that though.
I am of the mindset of Bogie: remove the heads. I think you are more likely than not dealing with a head gasket leak, and if it is not that you likely have a deformity or crack somewhere in a head casting. Last possible source in my mind would be just a surface irregularity in a head or block surface. There may be other causes but most water leaks into the combustion chamber are from head gasket issues unless the block was bored way out and there is a porosity in the casting between a water jacket and the cylinder wall. You have to remove the heads to check all that out and at that time you can see for yourself evidence of where the water is originating and where it is going, hopefully.
Not to start a war here, water leak into the cyl is not all that uncommon for these motors especially with some miles on them, have we sprayed carb cleaner around the intake to find a leak? Head gasket water port leaks are also common with miles. Verify the intake is not leaking by removing it, if you follow the doomsayers, remove the heads, rebuild the motor ect, you have to remove the intake first anyway. Start off slow, with no knee-jerk stuff.
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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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Are you indicating that the gasket and the intake don’t cover the port roof? If so that is an air leak.

Bogie
Are you indicating that the gasket and the intake don’t cover the port roof? If so that is an air leak.

Bogie
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?
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
Mike
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
Mike
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.
Typically, the 215cc heads are used with single plane intakes, which are typically taller and more solid in the needed area.

For a dual plane intake, you'll probably need a Performer RPM or clone like it. Weiand Stealth or Speed Warrior, the Brodix dual plane, Performer RPM Air Gap, Summit Stage 2....I'm not sure what all is out there that may fit.....I've always used single planes with heads like that.

Weiand Team G and Edelbrock Victor Jr are a couple of the single planes that make nice street intakes on 383+ cubic inches.
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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 .
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: https://www.summitracing.com/parts/fel-1003
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?

Bogie
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?

Bogie
I will do my best to find out, Bogie.
Josh , unless you have some affinity for felpro, google Competition Products ,they have Other affordable head & intake gaskets , work every bit as well as fel pro & are significantly less expensive ! Another thing to check when you get inside is head bolt length ( their are many different lengths available) & whether or not the correct hardened / ground washers were used . Anyone who would screw up intake gaskets like that makes anything else they did suspect , at best !
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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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Yes, there is a separate submerged cooler element inside the radiator tank.
Coolant in the radiator cools the element and the transmission fluid without mixing them.
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