3400 Common over heating issues?

[Honest Don]

could be a leaky heater core?

[Tbay99Venture]

This time of year wouldn't you see steam pretty easily? I've dealt with two of those and it was easy to tell even by a small leak between the coolant odor and the wifts of steam. Something like a van with rear climate control would be harder to spot though.

[3400-95-Modified]

could be a leaky heater core?

Oh it cold be, but there are no external leaks remember... so that kills that idea too.

I had a headgasket leak that did not steam much at all and did not have a very sweet smell of the exhaust... At least not at idle... under load it apparently consumed more coolant then, and would also make my temps fluctuate A LOT, I just pulled that motor apart last year to get it ready again for a daily application and both headgaskets had seeping leaks in the same spots. Last time I use Felpro headgaskets.

[Superdave]

I've seen heater cores leak to the inside.. you never see it till the puddle gets big enough to seep through the carpet.

[Tbay99Venture]

Head gaskest: the sequel

Oh it cold be, but there are no external leaks remember... so that kills that idea too.

I had a headgasket leak that did not steam much at all and did not have a very sweet smell of the exhaust... At least not at idle... under load it apparently consumed more coolant then, and would also make my temps fluctuate A LOT, I just pulled that motor apart last year to get it ready again for a daily application and both headgaskets had seeping leaks in the same spots. Last time I use Felpro headgaskets.

Well that's encouraging. I just got done bolting in a set of Felpros! And yes, before the job temps did fluctuate a lot but the leak hadn't progressed to where it was gulping coolant. At least it let go on a Wednesday afternoon instead of a Monday.

[3400-95-Modified]

I've seen heater cores leak to the inside.. you never see it till the puddle gets big enough to seep through the carpet.

I think a whole overflow tank would do that, and besides that a 99 alero has a heater core box drain, so it would go right to the ground.

[Superdave]

I think a whole overflow tank would do that, and besides that a 99 alero has a heater core box drain, so it would go right to the ground.

so did my 93 Z24.. still managed to puddle on the floor.


But back on topic.. OP, did you try the UV thing?

[shwgidy]

Tinkles,

I am going to redo my answer.

I think you have either:
-A crack in the radiator's nipple to the overflow tank
-A failed overflow hose
-A failed overflow tank

This would explain your coolant loss and your increase of air into the system.... The air gets in because the thermostat is working properly because its slightly overheating and thus open before it cools slightly allowing the air in. The coolant loss is only experienced when the engine is hot (when you are driving), thus no puddles.

If its a crack in the nipple you can use a smaller thin plastic tube to line the inside of the nipple and broken piece of nipple, then use hi temp epoxy to fix the crack...

Hope you let us know what it is/was.

-Brian

[Tbay99Venture]

Radiator plastic cracking

Yes, that epoxy works great but you really have to knead it well. We did that so we wouldn't have to scratch a road trip. The tank near the inlet to the radiator had a long hairline crack. Clean the plastic really well. I was worried about the stress near the hose fitting so I wrapped that with a bit of steel wire and a wooden shim then gooped it all with more epoxy.

[chri0029]

There are a few common cooling problems with the 3400 cooling system. First, the fan temp cal is way too high. The stock cal has the low fan turn on at 223 F and the high fan on at 230F. By the time the coolant at the coolant temp sensor senses 230 F and your fan kicks on, your coolant is way hotter at the opposite side of the head. Due to the design of old coolant flow (in which it was redesigned in later engines), the coolant can then have localized boiling and eat away at the cylinder head gasket. The CHG was redesigned a few times - first composite, then graphite, and finally MLS. If you pull your CHG and look at it closely, you can often see combustion ring cracks which allow a minute amount of combustion to make it into your cooling system. A CHG replacement will fix this problem, but only for a matter of time. The real fix is a fan cal change.

[Tbay99Venture]

Localized heating

Thanks for the background. I hope I'm not dragging the thread off topic, but I wonder if that's been known to cause bolts to stretch a bit as well. The CHG failure I had was a small leak for cylinder #2. Turned out the bolt at the front passenger side corner of the block broke free *much* easier that the others. It's the one with the unthreaded extension that locates in the hole of the engine mount bracket.

Now to find where to recal the fan temps in the PCM...

[chri0029]

Low bolt load is always a head gasket killer. But you can't assume you had low bolt load from low break-away torque. Although they are often correlated, the friction in the block threads sometimes behave differently. Try measuring the length of the bolts and see how much that bolt yielded compared to the others. Or the head structure could be different at that spot compared to the other locations. Or the bolt could have been undertorqued or overtorqued last assembly. There are many different possibilities. But a local coolant boil would only cause cavitation, not bolt stretching unless the head got really, really hot and grew substancially in that location.

[60dgrzbelow0]

Low bolt load is always a head gasket killer. But you can't assume you had low bolt load from low break-away torque. Although they are often correlated, the friction in the block threads sometimes behave differently. Try measuring the length of the bolts and see how much that bolt yielded compared to the others. Or the head structure could be different at that spot compared to the other locations. Or the bolt could have been undertorqued or overtorqued last assembly. There are many different possibilities. But a local coolant boil would only cause cavitation, not bolt stretching unless the head got really, really hot and grew substancially in that location.

^
X2.. An emphasis here on "Chasing the Threads in the Engine Block" with a new Metric Bottoming Tap in a very fastidious manner can also help to avoid the subsidance of Torque Squeeze after the engine is cycled a few time through the gamut of heating and cooling that will certainly contribute to the loss of Block-Gasket-Head integrity. The thing here is to do this regardless of whether or not the block has been re-machined in a Machine Shop...and especially if the head replacement is being done with the engine "In Situ" and those usual expected block cleansing fineries are subject to being overlooked. Rust... Dirt...Sealants... and Carbonized Mung in general... all conspire to ruin a good fit between the lightly oiled new bolt threads...and the threaded holes in the engine block.

"It Goes Without Saying..." (Like HELL it Does!)...that the Bottoming Tap is NOT to be used in an Electric Drill to sort of "Speed things along..."...NO!... This job requires bolt hole "cleaning" by using a Bottoming Tap fitted securely inside a decent "T" Handle to hold the tap and its purpose here is NOT to cut any new threads... it simply serves to very carefully clean the in-dwelling threads in the engine block of all the aforementioned dreck and detritus and make the threaded holes 'factory fresh' again. Take your time and do this slowly and methodically.

http://www.youtube.com/watch?v=j8m1F5ObOQI

http://en.wikipedia.org/wiki/Tap_and_die

..and just for the still image exemplar value (make certain the one you use is sized metrically accurate to your engine block head bolt holes)

http://www.amazon.com/1-25-High-Speed-Steel-Bottoming/dp/B0006G4MWU