OK fine I guess it wasn't my last post lol

That is my thought, too, especially since I KNOW coolant IS moving. But I can't get away from the idea that with less flow, air is more likely to get stuck somewhere. When cold, its air, and prolly just moves around. When hot it's steam, and blocks coolant flow, thus the overheat. Less flow = air not moving as fast = hotter steam = coolant flow stops = overheat. Had the flow been normal, apparently any air leftover after bleeding is supposed to work it's way out the overflow tank (that's what dealer and others have said).

Yes - always. And I have always had good, HOT heat through all of this.

Grab a beer or coffee: this is a long one lol..........

Assume that is is in fact always getting air introduced into the system, cause by a combustion leak or whatever from blown head gasket, and that's why I cannot get the air out, after a whole month and literally dozens of bleeding attempts. Unless it blew on my way to the shop that very day, and coolant started leaking out of the pump immediately, why didn't the gauge behave this way before? If head gasket is leaking now, why can I hold it at 3500 rpms for a full minute and gauge doesn't budge? Why did compression/leakdown/hydrocarbon tests all pass? Yesterday after I drained/refilled it, with radiator cap off, at one point I had it running for at least 5-10 minutes WITHOUT seeing a single air bubble surface at the radiator neck. This is with it sometimes idling, sometimes revving, watching it like a hawk the whole time. I understand that any one of these issues by themselves wouldn't guarantee that it's not the head gasket, but you put them all together, and you can only conclude it's not the head gasket. I give up lol.

I just think the guy who did it is not very competent. But, the "official" instructions say that to replace the water pump, first disconnect the neg. battery cable. If he did that, maybe it shorted the sending unit/gauge? That would fit with the fact that the engine doesn't really behave like it's overheated, although when gauge spikes hot, I ALWAYS get either pure air, or bubbles and steam from the tstat bleeder. When gauge spikes, but not too hot, I ALWAYS get pure coolant, like I should. So something IS happening related to temperature. There is definitely air in there.

In my mind there are two, and only two, possibilities. And keep in mind that no coolant is leaking anywhere, and there's no evidence it's being burned.

1. Air is constantly being introduced
2. Coolant is not moving fast enough

#1 is a no-brainer: I've been bleeding for a month, and actually getting a lot of air. It's hard to say though how much, and now that I drained/refilled yesterday (and actually got it to take almost another quart) I would say this is starting over as far as how much air is in there. But, as you'll see in my explanation for #2, I think I still just haven't gotten all the air out.

#2: I think the pump is crap, and I think the hGasket is fine. Maybe the lower grade pump vikesfan showed *SHOULD* pump enough, that doesn't mean that that's what it's doing. Maybe there is crap in there, too, blocking something. Tell me what you think of this theory:

Residual air (after initial burping) is supposed to make it's way into the overflow, and be gone forever. This is obviously not happening. Last week when I drove around for 2 1/2 hours, I got alot of pure air. The last couple times I got only steam/bubbles. Yeah - it's a closed system, but I can't believe it's sealed perfectly like a space suit. So during normal operation, air will inevitably get in somehow. If coolant is moving properly, this should not be a problem - it's supposed to go out the overflow. But if it's moving slower, maybe much slower or even stopping sometimes, these air bubbles become steam bubbles around the water jackets. Maybe they then start to gather into bigger ones, and you get a cascading-type effect. If they are gathering in the upper hose, which is a (local) high point, coolant flow from engine to radiator would stop altogether. Then ==> gauge spikes. BUT: the pump IS working at least a little bit, and the system is closed, so eventually something's gotta give. Then ==> gauge drops. And the whole cycle starts all over again. There's a 195 tstat in there. Several people have said that when tstat is surrounded by air, it will close, no matter how hot the air is, since a liquid transfers heat much more efficiently than a gas. That's just simple physics: 70 degree water "feels" much colder than 70 degree air on your skin. The main thing is I don't think the air is getting trapped in the upper hose or tstat housing where it could be let out that bleeder. But it's definitely getting trapped somewhere - prolly just not in a place where it can be bled out when hot and pressurized.

Apparently the top of the radiator is lower than the top of the water jackets; that's why there's bleeders. But if the air never makes it to these bleeders, that's irrelevant. I have NEVER been able to get air out of the bleeder on the line going to the heater core (maybe once or twice but I don't remember). This bleeder is the highest point in the entire system. If the coolant is moving properly, it should go out the overflow once the system is pressurized.

When I first got the car back, the gauge spiked FULL HOT & hot light came on 5,6,7 times or something. Could this have CAUSED a short? (I know - anything's possible). It hasn't spiked full ever since (did lots of bleeding attempts), but then again I usually pull over right away and see what comes out of the bleeder over the t-stat.

Something interesting happened when my wife drove it. I told her to be careful. She said it spiked (like 3/4 or 7/8), she pulled over right away. Shut car off. Then immediately turned key to on, but didn't start it (don't know what possessed her to do that lol). Gauge immediately dropped to just under 1/2. When she shut car off, coolant would have stopped, but maybe that allowed air to move and engine became flooded with cooled radiator coolant, but I don't see how it could have ACTUALLY cooled that fast. Plus, if slow moving system is the problem, this event doesn't make much sense. If this is nothing more than a faulty sending unit, I will scream. That would be just as coincidental as blowing the head gasket on the way to getting it fixed.

If only I had a 3D model of this engine to look at. I could prolly say: "I'll bet the air is getting trapped here, here, or here. I doubt GM would send me their autocad files though....

PS: I'M DONE CHASING MY TAIL DAMMIT. I'm gonna make the guy take the pump off (why should I have to do it?); just make sure I'm there when he does it. And replaces the new one...

 

the hole has absolutely nothing to do with flow or a failsafe, what it is for is to allow the burps of air and bleeding of coolant to go smoothly. since the system is sealed and pressurized system, that hole allows trapped air to escape when the tstat is in the closed position.

it makes bleeding the air go a lot smoother and easier.



which is why i suggested to him to get a scantool that can tell you what temp the sensor is sending to the pcm/dash.


also re: the shorted wire, normally, if there is a short in the coolant sensor wiring, it shows no heat, or over heating, no fluctuation. the sensor resistance could cause issues, which then could show variations in the dash gauge temp, but using the scantool will confirm/deny this scenario.

 

fyi, when you see the bubbles when its heated up and you have the radiator cap off, you have compromised the system since coolant and water under pressure have a higher boiling point.

stop taking the cap off of the radiator unless its cooled off!

 

the steam/gases is causing the spikes. steam/gases ONLY comes from boiling coolant or combustion gas. air cannot come into the system any other way if the fluids are topped off. since you have bled the systems many many times and air continues to be in there. your issue is NOT from trapped air. your issue is that is gases are being forced into your coolant and my guess, since the beginning, is the head gasket. i will almost guarantee it at this point. not the pump. the coolant passages are designed that when water is flowing, the air bubbles come to the top and are fed into the radiator and when cooled down, the air pulls coolant from the overflow bottle to replace the space the air took up. there are no hidden passages that will "hold" air forever. they do come out after just a few driving cycles.

you may have done the HC test, but the problem is, that the head gasket may not be leaking at idle, which i have said before. your symptoms only happen while driving, not at idle. there is no way to test for HC's while driving. the reason why the head gasket leaks while driving is because the compression levels are higher due to the resistance of moving the whole car (at idle, it only has the crank/pistons to move and the compression "force" is less).

i do not think it is the pump, but it could be, have him prove to you which pump was used. put in the better option (if he didnt already) and see what happens. my hunch is that the issues will continue.

 

I agree a scan tool and a pyrometer should be the 'go-to' equipment, but it sounds like it's not readily available. I also understand about resistance in the wiring, but see things a bit differently. If the wire has worn insulation or a dirty/loose connection it would cause variations in the gauge reading because of the fluctuation in resistance. If the wire positions itself so it becomes a direct short (via vibration and road conditions) the gauge will peg itself in the hot position. Another vibration and the short becomes intermittent again. and the gauge fluctuates. I'm simply suggesting things he can diagnose and eliminate as the cause without having to invest anything but a little time. If it does end up being a bad wire/connection it won't be the first time I've seen it.

There is a user on another IB forum (ASE Master Tech, L1 Advance Engine Performance certified) that has a quick and simple trick (post #6)you can try to determine if you may have bad wiring or possibly a defective sending unit:

Temp Gauge - Chevrolet Forum - Chevy Enthusiasts Forums

 

a probe with light will check the same thing. i actually had the short/ground issue with mine just a few months ago when i finished my top swap.

if you wiggle the harness around enough, it will become a perm short/ground issue. since his isnt pegging out all the way, i seriously doubt that the wire harness is bad and shorted/grounded out.

just imo

 

vikesfan & 03SSLE: I see all of what you are saying, and thank you very much again. If it weren't for you guys I'd be screwed. I am only looking for the correct solution. Of course I don't want it to be the head gasket, but, if it is, obviously I have to accept that. The only reason I've been grasping at "other straws" to try & find the cause is that it's really hard for me to see how it could be the head gasket that caused the pump to leak in the first place.

I took the car in on April 17th because the oil pressure sending unit had been leaking for awhile. VERY slow at first, but then it got worse so I had to take it in. On average I'd lose maybe a quart of oil per month or so (yeah I was lazy about taking it in but I always made sure the oil level was good). He replaced that, and it has not leaked since. I realize now that I did not mention that in my very first post (I thought I did) - but I either forgot or I didn't think they'd be related. If a blown head gasket also caused the oil pressure sending unit to leak, then this is REALLY crazy - it means the head gasket has been blown for at least 6 months. It was on that day he showed me the water pump was also leaking. Assume it IS compression/combustion gases causing all this; that means air would have been starting to come in way prior to the 16th. If the oil leak is related, then air should have been coming in for MONTHS prior to the water pump change. And, how the crap could I NOT have the "chocolate milk syndrome?" I've been looking at the oil on the dipstick thru all this: NO bad signs at all.

If there is a satisfactory explanation for NO gauge spikes (and no other problems either) even though air had been coming in for (likely) WEEKS - but I don't know how long the water pump was leaking - then I will bite the bullet & accept that it's the head gasket. I know a guy who build engines and will help me change it for a case of beer lol.

Somebody told me it could have been the head gasket all this time and it was not until the system was compromised (i.e., water pump change) that symptoms started appearing. That makes absolutely no sense to me though - if combustion/compression air is coming in now, I would think the only way it could have made no difference before is if the thermostat was stuck closed or something. But then I would have no heat, and it for sure would have overheated, even if, for example, the gauge didn't show it.

Obviously it would really suck to change the head gasket & find out that was NOT it lol

Maybe the head gasket leak could have been VERY small to begin with, and steadily got worse. But then how would it cause the pump to leak BEFORE the gauge started fluctuating?

I borrowed a laser-temp-pointer, and will check things out, but I'm going to drill the hole in the t-stat tomorrow and see what happens. I've heard it said that if enough air begins to surround the t-stat, it will begin to close, because air is a lousy conductor of heat. If air is being shot in, and building behind the t-stat, and it begins to close, this definitely explains the problem. It also can account for the fact that the HC test passed: air was building for the 5 or so minutes he did the test, but this air would not have made it into the radiator at that point. Drilling the hole will definitely let air out. If this fixes the problem, and the head gasket WAS leaking, I'll prolly never know though, at least until I get the "chocolate milk". I guess at this point it doesn't matter...

 

you can also take the tstat out to do the hc test



here is my theory on why i THINK you have a toasted head/head gasket.....


i dont believe the gasket is bad, but i do believe that the head has become warped from the steam that is created. keep in mine, just because the laser temp says the engine isnt hot, that head is still seeing the steam, and as your coolant temp gauges is telling you, that it is very hot (in the red) and not cooling the head during operation causing the head to become very very hot from the lack of cooling. all it takes is for one teeny tiny hot spot to crack/warp the head. since you have been dealing with this issue since the very beginning, i believe what started out as a simple bleeding the air out issue turned into a warped head. warped heads really only show up after being warmed up and while driving (in most cases). now i believe you are not dealing with air bubbles that were trapped from the beginning but rather dealing with the escaping gases from the combustion chamber leaking out from the warped head.

that is just my opinion based off of what you have said from the beginning, which is also what i have said from the beginning. does it suck that this may be the cause? sure it does. but i do not believe you had the issue before, you have done all the right steps to clearing any trapped air bubbles, and the ONLY way for more to get introduced is by the escaping gases from a leaking head gasket due to a warped head.

 

Thanks vikesfan. One more question: is it really true that as air bubbles are passing thru the thermostat, it will begin to close? Think of it this way: if a 195 deg tstat is submerged in 220 degree liquid, it will open. If it's surrounded by 220 deg air/steam, it will not, or at least not as efficiently or something. What I think is actually happening is that air is building behind the tstat, and it begins to close, thus an overheat. I say 220 because I got that laser temp pointer & that's what the temp of the tstat housing was the last time it spiked (about 3/4 - so that does seem to match the gauge) and I got steam & bubbles out of the bleeder. For the two lines to the heater core one was ~ 150 & the other was ~ 120, both upper & lower radiator hoses were only about ~90. I can see how the heater line readings are accurate since they are metal where I pointed the laser, but it seems like I *should* get a much lower reading pointing it at a rubber hose that's prolly 1/8" thick at least.

I can't see where to point the laser to get the temp that is actually being sent to the gauge - I am not sure exactly where the sending unit is, but I do think it's under that cover that needs to come off to get at the rear three spark plugs. Pointed at the "structures" on the block directly "upstream" from the lower half of the housing that holds the tstat - also 220 deg

Can you give me some ideas on specific spots to check the temp? I would like to nail that down before drilling the hole, which might drastically change the car's behavior. As for the numbers I gave above, I only did it once, and that was the very first spike after going from cold.

That's why I still did not drill the hole in the tstat. If this is a head gasket issue, would it still pay to drill the hole? If I'm right about air being trapped behind the thermostat, then it's not making it into the radiator either. I would think that if air makes it into the radiator, it can come out the overflow tank. After all, this is how residual air is SUPPOSED to come out. I just have more air than normal, if in fact it is a head and/or gasket issue.

 

And I suppose it would be a lost cause to try and sue this guy. If leaving air in after changing my pump warped my heads, that useless f*cker just caused $1800.00 damage to my vehicle...