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I have a 92 S-10 2.8L 2WD Ext Cab Tahoe with 5 spd manual transmission. Engine has approximately 150k miles. I've been loosing coolant while driving. It doesn't appear to be much, but it is going somewhere that I can't detect. I replaced the radiator a couple months ago because the old one was clogged up pretty bad. I filled it with distilled water only and drove it. When I looked at the recovery tank the other day, I noticed the coolant had a reddish tint to it. I drained and flushed the rad and recovery tank, then refilled with distilled. I started the engine with the rad cap off to burp the air out of the system. I noticed a bunch of white foam coming to the surface of the rad. I've attached a few pics.

Based on the reading I've done, the two likely culprits are the intake manifold gasket and head gasket leaking. I have not seen any milky looking oil yet. The foam doesn't really smell strongly like anything. My next steps are to do a pressure check on the cooling system and possibly check the compression. Does anyone have any suggestions besides those two things that would help?
 

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4 Year Intermediate Tech
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As always with any engine I own I use 50/50 green antifreeze. Running plain water will cause increased corrosion rates and will not cool as efficiently. If you have a thermostatic fan clutch check it for correct operation, check the thermostat in the intake to see if it's stuck closed, check hose clamps at all connections, check freeze plugs for a pin hole leak, you can perform a compression test to rule out a blown head gasket, carefully inspect the intake manifold especially on the the back side for wetness. Check around the timing cover and water pump gaskets and the weep hole on the water pump. Also if you have oil leaks you can spot a water leak by looking for a light colored goo. When water mixes with oil it makes a coa coa milk goo.
 

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As for the foaming rad you can get a head gasket check kit that will sniff your rad for carbon monoxide.
 

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As always with any engine I own I use 50/50 green antifreeze. Running plain water will cause increased corrosion rates and will not cool as efficiently. If you have a thermostatic fan clutch check it for correct operation, check the thermostat in the intake to see if it's stuck closed, check hose clamps at all connections, check freeze plugs for a pin hole leak, you can perform a compression test to rule out a blown head gasket, carefully inspect the intake manifold especially on the the back side for wetness. Check around the timing cover and water pump gaskets and the weep hole on the water pump. Also if you have oil leaks you can spot a water leak by looking for a light colored goo. When water mixes with oil it makes a coa coa milk goo.
I had 50/50 in it before I flushed the system and replaced the rad. Since I suspected I was loosing coolant, I didn't want to keep buying and loosing $13/gal antifreeze.
 

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FWIW you don't have to have coolant in the oil or vice-versa, I went though this myself about a year or so ago. One of the fire rings on the head gasket failed and it allowed compression to enter the cooling system. And some coolant into the combustion chamber.
I was able to isolate the cylinder by pulling the plugs and found a wet one. I then put air pressure to that cylinder via air compressor to the spark plug hole and confirmed the bad gasket when pressure bubbled out the radiator fill.
 

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I may have jumped the gun on the foam. I ended up flushing the cooling system with the hose this afternoon thinking that I may still have some residual flush chemicals in the system. Refilled it with distilled water and ran it for about 20 minutes with no foam. I am probably still loosing it somewhere, but hopefully a pressure test will reveal something easy to repair.
 

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How quickly are you losing it? Maybe pushing it out of the exhaust... If its really slow, maybe pull the plugs like HJR recommend and look for a green tint.
 

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How quickly are you losing it? Maybe pushing it out of the exhaust... If its really slow, maybe pull the plugs like HJR recommend and look for a green tint.
I'm not losing it very fast. I think I may have figured out where it is coming from. Back about two years ago I had to replace the water pump. Last night after a drive, I noticed what looked like bubbles coming from the water pump gasket near where the A/C compressor and power steering pump are located. I rented a pressure tester and am going to try to confirm this evening. Good news from that is that the likelihood of losing it inside the engine is much lower.
 

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Pressure tested the system last night. A couple of my hose clamps were not tight enough from the radiator replacement. I also noticed some dripping on the back side of the block on to what looked like the bellhousing. I couldn't see from where exactly. I suspect the head gasket has failed in one spot and is letting water out from one of the jackets. This sound correct?

It's sad, because the engine runs pretty well and I'd hate to tear it down and screw that up.
 
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