Oil in Antifreeze

**Coyote** · 12-31-11, 02:21 PM

While draining the coolant system in preparation of engine removal, I noticed that the antifreeze has a black oil film on top of 5-gallon bucket where I collected the coolant (yes, it was a clean bucket!). I have oil in the antifreeze but there was no antifreeze in the engine oil when I drained it. Since there is no engine oil cooler and no transmission cooler on a LT-4, am I to assume that there is a cracked head or a head-gasket issue? I was pulling the engine to fix external oil leaks that have been bugging me for years when I noticed this problem. I hadn't planned to pull the heads off but since I already have the engine out....
The car only has 56,000 miles on it and no engine problems of any kind.

**Toms01** · 12-31-11, 02:31 PM

Well Coyote, first off welcome to CAC. You've come to the right place for help. I believe that you have diagnosed it correctly. I'd guess it is a head gasket (and really hoping it is rather than the alternative). I would guess that others will check in here and give you more and better information.

**bill81vette** · 12-31-11, 03:19 PM

Welcome to CAC!!!
usually its the other way around as the oil has more pressure than the coolant,
at least until the engine is cold.....
Is there a lot of oil???or just a film of it...

**Coyote** · 12-31-11, 05:03 PM

Yeah, there is definitely no antifreeze in the oil. I've had the car for 5 years and now that I think of it, I noticed that the overflow reservoir was always "dirty". I removed it once not long after I bought the car and washed it out but after a while it was "dirty" again. Didn't think much more about it since there were no other symptoms. The car has never run hot. I have a 160 degree thermostat in it and I haven't seen it much higher than 170 since I put it in except while idling in traffic. No other blown head gasket symptoms either. No miss, no steam, no smells... nothing. I can't do a compression test since it is on an engine stand. I have just about convinced myself that the heads are coming off.
The coolant that I drained is in a 5 gallon bucket. The film seems to be maybe 1/8 in thick but that's just an estimate.

**bill81vette** · 12-31-11, 06:08 PM

I wonder if someone prior to your owning it used some 'dirty' antifreeze or a 'dirty'container
for the coolant.I can't think of a logical reason how it would get in there..
if the head/gasket were cracked/blown then there should be coolant in the oil,not the other way around,
without an engine cooler.

**Hib Halverson** · 01-01-12, 10:15 AM

Hard to fathom engine oil in the coolant, but it could happen, i suppose, if oil pressure, which is higher than cooling system pressure, could force oil into the coolant. I believe, the only areas where oil under pressure could leak into the cooling jacket are in the engine block. It would have to be a situation where there is a leak or a crack from an oil passage to the cooling passages.

There are no areas in the cylinder heads where oil under pressure could be forced into the cooling system. Also, with the Gen 2 V8 I don't believe there is any pressure fed oil flowing through the block/head decks.

How many miles did you go between coolant drains?

A film 1/8-in thick in a 5-gal pail of coolant is quite a bit of oil. Did the engine use oil? If so, how often do you have to add it?

**Coyote** · 01-01-12, 12:19 PM

The car had 50K when I bought it in Nov 2006. I have never changed the coolant since I have owned it. It now has about 56k. The reason that I pulled the engine in the first place is that it had an external oil leak that I could never locate with the engine in the car. I couldn't stand the oil spots in the garage any more! I never had to add coolant and it never leaked more than a quart between oil changes. It has never smoked, even when sitting for months. My original plan was to fix the oil leaks and that was it. While I had the oil pan off I did a bearing inspection and found some corrosion on the rod bearings so I replaced the main and rod bearings as well as the seals and gaskets. Now that I am thinking about pulling the heads, I wished that I had pulled the pistons and replaced the rings! I may end up just flushing the cooling system and putting everything back.

**gmjunkie** · 01-01-12, 01:58 PM

Originally Posted by Hib Halverson

Hard to fathom engine oil in the coolant, but it could happen, i suppose, if oil pressure, which is higher than cooling system pressure, could force oil into the coolant. I believe, the only areas where oil under pressure could leak into the cooling jacket are in the engine block. It would have to be a situation where there is a leak or a crack from an oil passage to the cooling passages.

There are no areas in the cylinder heads where oil under pressure could be forced into the cooling system. Also, with the Gen 2 V8 I don't believe there is any pressure fed oil flowing through the block/head decks.

96 with 56k.......Check the weep hole in the water pump,I'd bet it started leaking from setting around and some A$$hole dumped a big Bottle of Barr's Leak in it!~!!There should be some sort of evidence at the weep hole if so!

That SH*T looks just like oil floating on anti-freeze after it's been drained!~!!

**LLC5** · 01-01-12, 02:55 PM

Originally Posted by gmjunkie

That SH*T looks just like oil floating on anti-freeze after it's been drained!~!!

Yes it certainly does. That very well could be all it is.

**Hib Halverson** · 01-02-12, 12:17 PM

I hadn't even thought about a system with stop-leak in it.
Silly me.

That's why, thankfully, we have pros like the "Junkie" around here.

**Toms01** · 01-02-12, 12:42 PM

Great call Junkie.......

**Coyote** · 01-04-12, 08:09 AM

I sure hope that it is stop leak. The guy that sold me the car said that the water pump had failed while the car was under warranty and that was the only work done to the engine. My version of "Stop Leak" is that I fix the leak! I'm not a big additive guy so at least I will get this stuff out of my cooling system. I just don't want to remove the heads if I don't have to. I'm going to pay a visit to my local machine shop that I have been using for over 30 years and talk to my buddy there. Maybe a picture for all you interested would be helpful?

**LLC5** · 01-04-12, 08:24 AM

Originally Posted by Coyote

I sure hope that it is stop leak. The guy that sold me the car said that the water pump had failed while the car was under warranty and that was the only work done to the engine. My version of "Stop Leak" is that I fix the leak! I'm not a big additive guy so at least I will get this stuff out of my cooling system. I just don't want to remove the heads if I don't have to. I'm going to pay a visit to my local machine shop that I have been using for over 30 years and talk to my buddy there. Maybe a picture for all you interested would be helpful?

Quite a few auto manufacturers are recommending to add their own brand of sealer during a cooling system service, and I know that GM does sell it in their parts department, so it is possible that someone installed it during a service. I am not saying that it did indeed happen, only that it could be possible. Definately have your machine shop buddy look at the coolant. Good luck with it.

**Hib Halverson** · 01-04-12, 09:45 AM

Dealers may recommend the stuff all the time because it sells parts/accessories but GM Service Manuals stopped recommending sealant (those "pills" you put in the coolant) at the end of the C4 era. With C5 and C6 I've never seen it recommended for normal or general use in the Gen 3/4 series engines.

The problems with sealants is that some layperson/consumers are under the impression that if a little sealant will fix a little leak, that a lot of sealant (i.e.: repeated applications) will fix a lot of leak. All these sealants work by coating the inside of the cooling jacket with a pliable "sealer" that gets "sucked" into small leaks, thus sealing them. Problem is that sealant, because it coats the entire cooling system, also increases coolant temperature somewhat as it interferes with the transfer of heat from the hot engine parts to the cooler coolant flowing through the system. This is why engines which have undergone multiple treatments with sealant or "stop-leak" products tend to run hotter than engines which have not had sealant introduced into the cooling system.

I'd say that if that 1/8-in of oily stuff on top of the drained coolant is, in fact, stop-leak residue, it's likely the engine had been treated more than once.

**Coyote** · 01-25-12, 03:59 PM

I took a clean baby food jar and sampled the antifreeze. I took it up to a machine shop / auto parts place that I have been doing business with since the 70's. The first thing Jimmy did was to smell it. He said that if there was oil in it that you would be able to smell it. He then poured it into a white styrofoam plate. He then poured some new Dextro into another plate and compared the two. There is a antifreeze test strip (kinda like litmus paper) that tests the antifreeze for three different things. He tested the new and mine and compared the results. They were pretty much the same chemically. My antifreeze was a little discolored and he said it smelled burned as if the engine overheated. That surely hasn't happened on my watch so I'm not going to pursue the issue further, except to put new antifreeze back in when I put the car back together. I learned a lot about antifreeze that I didn't know, especially how many different types and colors there are!