Signs of engine trouble via coolant

Ok so last weekend the car started running hot, I have a gauge and a light, the gauge started approaching red, as soon as the light came on I pulled over, a hose busted and the guy I pulled over at actually had an old hose, put it on and filled me up with water, I was completely empty

ok so here's a little history, the intake on the 3100 has been replaced recently, I didn't do it but it appears to have been done well, I can tell by new gasket sealer on valve covers and at bottom of intake. and also the reservoir had old muddy **** on it but coolant was clean

haven't touched cooling system at all, but that weekend I flushed and changed all hoses, nicked the radiator and then when back to replace it, when I dumped the second time as I tilted the old radiator to the side where the bottom contents could finally come out, I assume they didn't just by putting a water hose through it I found oil but only after the last bit ran out, since the tank was never cleaned and the radiator never changed before I am assuming this was from previous gasket failure.

well what i'm seeing now that im paying more attention is tiny little floating greenish patches in my dexcool, very small and just in the neck of radiator and not very much at all, the overflow coolant doesn't have them, if I towel them out then squeeze the top hose several times to get coolant moving no more appear. ive also noticed a tiny blackish residue on the silver part of the cap from time to time, im not talking bad like all the google searches but just a tad and its stickish and not oily, plus its black and my mobile 1 synth is golden yellow, also no signs of milky oil.

So I went and scrubbed the absolute crap out of the overflow thinking maybe it could be dislodging mud, it is spotless now, the only spot I could not get was the one inch part of the plastic where the hose goes into the tank. still showing up

recently threw o2 sensor code, it had done this before once too before issues, and plus I don't even really know if this was happening before I got the car because its very suttle and when I pulled the cap at dealer it was clean. anyways pulled o2 sensor and had just the simple whitish color they all have after 100k miles, new one in and car runs the same, I think the heater was shorting in it bc that's the code I would get. no smoke blowing out pipe of any color, no strange odor. car runs like a champ, it has a very tiny miss at idle but it has always had this and ive had an alero with the 3400, basically the same, and it developed this over time as well but it ran to 300k miles only needing an intake gasket and a tranny solenoid.

in the process of overheating the temp sensor burned out, I would start a cool motor and it would ping over hot, but when disconnected it would drop to 0, so I replaced it and now notice that it normally runs dead center instead of 1/3 the way up, I chalk this up to bad original sensor from start and the heat just threw it over the edge, so with ac (fan always on) on in 100 degree weather the car stays right around dead center no issues, but with no ac it starts to rise when sitting still until fan comes on but its closer to the red than I would like it to be, either the gauge just reads high at top end or the fan is not kicking on at proper time, it did this with old temp sender (3 wire) I have light and gauge, I don't know if this sensor is responsible for fan times, but I think it probably is since its a 96 century and most likely uses one sensor and the computer does the rest. while moving at high speeds with fan off it stays cool, or cools back down after a good while, only thing not replaced is water pump (its not leaking) and thermostat, which appears to be opening at dead center on gauge so it looks good.

my main question here is that is this a sign of a problem? no internet search has shown same issue as mine, they all show radiators full of mud or black oil mixed in bad enough you know what it is. last time I had the issue with the 3400 the oil was the first thing I noticed as it started to run hot, it was chocolate milk, then when I checked radiator it looked real bad too. so is this a very early sign of a problem? or just normal dexcool issues or the fact that I can never completely flush the heater core / engine 100% with a water hose. I am going to be starting to use this for long distance camping trips in the fall and don't want it to blow and leave me stuck. I have cleaned the engine and see no seepage anywhere on the outside of the intake or heads, but smell oil occasionally just barely, I think the front main may drip a tiny bit. it almost never reaches the driveway and the one time I noticed it, it was a dime size drop after spreading out. what are everyones thoughts on this, I usually don't see this, and they aren't orange splotches like ive seen before in dexcool that is deteriorating. maybe old engine coolant sealer (is any of it greenish or a color that would appear greenish (dark green not bright regular antifreeze green). what should I do, just drive the **** out of it and see what happens.

something very suttle in antifreeze, no detectible coolant in oil, no detectible oil loss or coolant loss, no detectible engine troubles or smoke. head gasket / intake gasket in stage one failure, old contaminates in cooling system (sealer, old dexcool that couldn't come out, oil from previous failure?

 

You didn't mention the thermostat. Has the car been sitting?
Blown hoses and rads from my experience are a result of a stuck thermostat.

Shouldn't mix the green stuff with the orange stuff.

If it's running ok I'd flush it out again, refill, and run it hot a few times while checking the colour of the coolant.

 

Did not mix, car has sat but hose was old. It's the common culprit. I busted the radiator by accident. Then opens right bc it goes right up and stops on gauge same spot everytime

 

It's a well-known fact that even with a 195* t-stat, the actual temp regime the computer uses can take the temp above 230* F before kicking the fans on. I've dealt with a few dozen of the 2.8/3.1/3100/3400/3500 engines in all different GM cars and they all work about the same. As for the Dex-Cool cars, no matter how much flushing you do, there's always a missed pocket when you just rely on a garden hose. That's why I'd also carefully use compressed air to jog the liquids up and loosen settled crap in the bottom of the block and inside the heater core.
How many miles on the car? Has any of the other hoses been replaced, or are they original? When the intake gaskets were done, was the t-stat replaced? I always replaced the t-stat on an intake gasket job, whether it needed it or not. Also, You might want to check the snugness of the bolts on the lower intake, just to make sure the bolts didn't loosen. I always ran through the torque pattern on the lower and middle intakes three times to ensure the pieces were properly settled to seal (lower only if a 3100/3400/3500). And remember, when the A/C is off, the computer only runs low fan for cooling only, unless the ambient temp is above, IIRC, 105*, then it runs high fan for cooling only.

 

I didn't replace it previous owner did via a shop I'm sure bc they were well educated and lived in a nice neighborhood via the stickers on the glass and condition of car. It just sat for awhile and was finally used as a trade in to get it out of the way I'm sure tstat probably changed. When hose 1 busted I changed every water hose including heater and the tiny one on throttle body. Car has 99k miles. Gasket looks like it had been replaced within the last 20 or so because the gunk in overflow was all hardened and required scraping out. I may be over worrying about it. It's something a mechanic without hooking any testers up would say hey no probs. But you know they don't catch then sometimes till its gotten bad enough to tell

 

The one thing I would not trust is believing a mechanic did something. I not only would go ahead and put in a new t-stat, even though it's a MFing b!tch to do on that 3100 (only use an open-end 10mm after you break the bolts loose), and if the radiator cap is factory, replace it. Then, the horror: how much air bleeding are you doing once you begin refilling the cooling system? All of those effing engines will keep holding on to air, and I've had cars that I've had to carefully bleed off air more than five times after running the engine to hot and watch as it comes pouring out the radiator neck. Once it's properly air-bled, it'll properly keep the engine protected.

 

I think I'll forgo the tstat for now. It seems to me it's working and when sitting still with no ac which would almost never happen it does rise in temp a little but then fan comes on. I've tried this on my alert it was a bitch and I pulled out a perfectly fine tstat. Oh yeah I do almost all my work. And would not let them diagnose me with head problems unless I saw the Chem test done myself. I'm thinking I'm being too paranoid if it was a break between piston and water jacket combustion would not let it stay so small if it was a link between oil and water it would be in my oil by now I've put several hundred miles 200 to 300 on it since coolant system sealed up for good. My only other thoughts are some hairline Crack in block or head which means I'll basically need a new motor anyways. Will just run her a good bit this summer and keep my eye on fluid constancy and levels.

 

Sounds good and I think doing those t-stats is what gave me left hand arthritis....

NO comments from the Peanut Gallery!

 

That's your story.. Stick to it!

 

Yeah I'm hoping it's ok I think just small debris is getting worked out. I found a spot the size of a pencil eraser at the bottom of the overflow tank didn't look like oil that coagulation but more like dirty sand, couldn't be more than an amount that would fit under a woman's fingernail. Oh and I've always bled these things till my eyes are blue too lol

 

A lot of guys don't know about the block plugs that are in each motor. They are located at the bottom of the block water jacket. When you drain an engine by the radiator petcock or by removing the lower hose, you are only draining the block to the level of the water pump hole, which is usually mid-block, Any sediment in the system settles in the bottom of the water jackets around the cylinders and the only way to get rid of it is to remove those plugs and flush it that way. For really badly rusted coolant, sometimes the only way to get rid of it is to blow out a freeze plug and stick a high pressure hose into the water jacket itself.

With every vehicle I've ever owned, one of the first things I do is to replace those block plugs with brass petcocks in case they are needed down the road for flushing purposes.

 

I remember when engines had brass drain petcocks in the engine blocks. Maybe someone added them but I was always lucky.
Now I can't even see the block!

Image years ago when we used to have to drain, fill, and flush the antifreeze every spring and fall.

Or back when they only used water and drained it every time they went to town and back.

 

I think I've come to the conclusion that this is either leftover stopleak from before intake repair or just dirt or minerals from tap water making their way to the tank. No oil floating on top so I should be good.

 

Drive it, enjoy it, keep an eye on it!

 

Back when I first started in the business, permanent antifreeze wasn't popular yet. Instead it was made from methyl alcohol. Every spring and fall, we were deluged with flush jobs. The alcohol wasn't permanent and would boil in hot weather. It was replaced with plain water for the summer months. Since all customers were local, twice a year repeat business, installing petcocks was part of the package just to make our job easier.

This was also before oil filters became standard. When changing the oil, we had a siphon with a hose on it. It was put thru the drain plug hole to suck out sludge and accumulated lead residue from the gas. The sludge was gray, not black.