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View Full Version : 3400 Common over heating issues?



Tinkles
03-20-2010, 04:47 PM
My little bro has a 99 Olds Alero(63k miles on the clock) with a 3400 and is over heating quite regularly. I have changed the T-stat, there are no visible leaks, no coolant in the oil, no puddles, no exhaust smoke at all. We dropped it off at a "garage" and they did was bleed the air out of the system, not find out how it got in there in the 1st place. Im usually pretty decent with diagnosing problems, but im clueless with this.

Are there any "common" cooling issues? Any ideas?

Superdave
03-21-2010, 11:08 AM
heater core is one regular way air can get in the system.

get some of the UV dye at the parts store and a UV flashlight, run that through the coolant system for a while and you should be able to find the leak.


Welcome to 60degree!

shwgidy
03-21-2010, 12:01 PM
Check the oil for coolant milkshake.

Tinkles
03-21-2010, 02:00 PM
heater core is one regular way air can get in the system.

get some of the UV dye at the parts store and a UV flashlight, run that through the coolant system for a while and you should be able to find the leak.


I'll try that, thanks.



Check the oil for coolant milkshake.

I already said the is no coolant in the oil.

60dgrzbelow0
03-21-2010, 09:32 PM
Generally... air trapped in the cooling system that migrates into the water pump housing immediately diminishes the ability to move the coolant around, since the water pump impeller is designed to act against the incompressible fluid. The best way to solve this problem is to find either the actual "Bleeder Valve(s)" on your engine or the highest point in the cooling system where the air bubbles can amass that you can let the air out via an un-clamped hose. Before you begin by starting the engine in the driveway with the hood up and a garden hose handy... mix the water in a 50/50 ratio with the kind of new anti-freeze that your car manufacturer recommends. Avoid "mixing your colors" (say...orange with green) here as you may have issues later on that are unpleasant if their chemistry is incompatible. Then, with the radiator cap in place and tight and the coolant overrun tank filled to the proper level, start and run the engine at idle until you begin to see your thermostat rise. Then, when the engine is nice and warm...just open the bleeder valve(s) that are probably located somewhere along the line where the heater hose(s) come off the water pump manifold. Your Haynes or Shop Manual will be your guide to find them. Do this long enough to sort of "Burp the Baby" of all of the air pockets and let this go on until you see a steady stream of coolant coming out. Then just snug the valve(s) closed and check your dash panel temp gauge for any changes that show the temperatures are lowering and then take the car for a 10 minute drive to see if the engine temp continues to behave. When you get back in the driveway... let the car cool down and top off your radiator and coolant tank at the "COLD" level and look over the engine for any coolant leaks from the bleeder valves. This will almost always solve the problem. Please dispose of any extra anti-freeze in a responsible manner, as "PEG" (Poly-Ethelyne-Glycol) has an attractive odour and sweet taste that animals enjoy lapping or drinking and it invariably paralyses and kills them...mostly local dogs... who might wander up after your job is done and get into trouble if they find the stuff.

Tinkles
03-21-2010, 11:52 PM
I already know how to bleed a cooling system. My concern is HOW did the air get in there in the 1st place. The car is losing coolant w/o any signs of external or internal leaks.

19Cutlass94
03-21-2010, 11:57 PM
I know on my car, the WP gasket leaks a little, but theres never any dripping. Its leaks slow enough that its just steam. but it leaks enough that I loose coolant over time. How much coolant are you looking in what period of time?

Tinkles
03-22-2010, 01:48 AM
It'll empty the overflow tank in a 20mile trip.

asylummotorsports
03-22-2010, 07:38 AM
Pull the spark plugs.

If you have a REALLY clean one, you have found where the coolant is going.

As well you may want to check the pressure cap.

3400-95-Modified
03-22-2010, 09:32 AM
It'll empty the overflow tank in a 20mile trip.

Then you are burning it in the cylinders via a leak on your headgaskets which is also causing your overheating issue, OR you are leaking into the motor and mixing with the oil.

60dgrzbelow0
03-22-2010, 01:27 PM
Then you are burning it in the cylinders via a leak on your headgaskets which is also causing your overheating issue, OR you are leaking into the motor and mixing with the oil.

... and A/F PEG in the motor oil is very nasty and corrosive on Babbitt bearing surfaces...

Tbay99Venture
03-22-2010, 02:26 PM
Here's an example of what you find if the leak worsens.

http://www.youtube.com/watch?v=VImQZDfxAyg&feature=related

Not that I know these guys or anything, just was looking around on the subject.

Tinkles
03-22-2010, 05:15 PM
I already said there is no signs of it burning coolant or coolant mixing with engine oil. Anyways the damn thing has been dropped off at a garage with the proper diagnostic tools.

3400-95-Modified
03-23-2010, 01:32 PM
I already said there is no signs of it burning coolant or coolant mixing with engine oil.


Ok, I can understand the lack of evidence for mixing with the oil and claiming thats not the issue, but what proof do you have to say its not getting burnt?

There are three places coolant can go when your "using" it...

1) The Ground
2) Oil
3) Cylinders

You've already ruled out the oil since its NOT brown and not gaining capacity... and you've already said there are no puddles or visible leaks. So that leaves ONE more route... and that does NOT always result in exhaust smoke, it all depends on how severe the leak is.

This isn't magic, it has to go somewhere, so your missing a big leak somewhere, or you just don't want to take our advice about it possibly burning it.

I'm curious to see what the "Mechanics with the proper diagnostic tools" have to say about your issue... Please inform us when you know. IIRC you've already brought it there once and they simply bled the air out of the system... Where were their tools then?

Sorry to come across like an ass, but your asking for our advice and then you beat down every possible solution we present, but at the same time you're asking because you don't know the solution to the problem right?!!? At least give our advice a chance and re-explore the avenue's we are presenting to you, because obviously something is being over looked.

I'm really sticking to leaking headgasket though. You have two of the most common symptoms of a bad headgasket, repetitive overheating and coolant loss.

Tbay99Venture
03-23-2010, 02:22 PM
I just got done replacing the head gaskets (3.4L) going on 3 weeks ago. I've done a few of them on different cars now and this was a small leak but at least was making white exhaust. The plugs really didn't have any differences between 'em but the compression reading told the story.

My most spectacular fail was on a Toyota inline 6 with the alloy head. My wife and I had stopped to get a video tape and by the time we got back in there was enough water in the cylinder to jolt the starter to a standstill. :mad: With another friend we got it push started and left with a trail like a steam locomotive. Still ran w/o problems after a re-gasket. :)

Honest Don
03-23-2010, 04:52 PM
could be a leaky heater core?

Tbay99Venture
03-23-2010, 10:07 PM
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
03-24-2010, 06:26 AM
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
03-24-2010, 07:06 AM
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
03-24-2010, 08:15 AM
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! :confused: 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
03-24-2010, 09:42 AM
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
03-24-2010, 10:11 AM
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
03-24-2010, 11:06 PM
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
03-24-2010, 11:14 PM
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
03-25-2010, 09:13 AM
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
03-25-2010, 09:55 AM
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
03-25-2010, 12:13 PM
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
03-31-2010, 08:24 PM
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