I've thought about that a lot mitch. Here is why I believe that its not a plugged engine block.

1. The whole stop leak, leaky radiator problem was several months before the car had this current overheat problem. I had flushed out the coolent since then... long before this issue began.

2. When coolant isn't flowing it usually overheats much more quickly than this car is. The car doesn't overheat until enough coolant has forced its way out of the overflow tank. The overflow tank when filling and sprewing... the fluid is not that hot... it eventually gets really hot if driven long enough... but it overflows even while still cold.

3. If it is a coolent flow problem... it would overheat on the freeways just as fast as it would on the street. It wouldnt matter how cool the radiator fluid was if it was not getting into the engine properly. It is the moment I get off the freeway that it begins to overheat... because the radiator is no longer being aided by the wind to cool what is left in the radiator by that time.

It is because it is overflowing and spewing before the engine even warms up that I believe that the coolant system is being overpressurized by some outside influence... which is forcing cool fluid out of the overflow tank.

I feel like I want to recheck the head pressure again more closely... but I had just changed the oil on the car with mobil 1 just a few days before I did the pressure check. When doing the pressure check you dump unburnt fuel into the oil (you have the plugs pulled) which ruins the oil. So I had to change the oil again after the pressure test I did. I think I'll barf If I have to pressure test again and ruin the brand new mobile 1 extended I just put in. 3 changes in a couple weeks I can't afford that

This sucks.

 

I had a Chevy Luv pickup with a 327 Covette engine in it (fun ride!). I constantly had over heating probelms with it, very similar to what you describe. I even replaced the radiator with an expensive 4-core radiator. I accidently cracked the crank shaft because I lugged the engine too much going over a small curb. Anyway, I sold it with the engine broken. When the guy tore it down he fixed the crank, but he also found what looked like big pieces of gravel at the input port of the water pump. He flushed them out (they were big!) and the engine never had over heating problems again. I had a mechanic look at the "gravel" and he said it was Stop Leak.

Maybe remove the water pump and have the block flushed? Its not that expensive (you might be able to do it yourself with a garden hose. Although higher pressure would obviously be better.

Also, try having the oil checked (or maybe it's the coolent) to see if one has gotten into the other. That's always a tell tail sign of a blown head gasket.

But you're right....this has got to be VERY frustrating for you.

 

so that's where the thermostat is!
I have seen this in illustrated diagrams before, but it's much more clearer when you see a pic of it like this.

 

I agree. if it was the head there would be tan colored floties in the radiator caused by the oil and coolant mixing.

 

Those pics did not show a very good angle I dont think and I was pretty dirty in there. I just sprayed degreaser all over and power washed the engine and took some more shots. Can someone point out where the bleeder valve is? Am I looking at the right thing?



New clean engine Yum!




I let the car idle for about an hour in the driveway while taking these shots.

As I've said the bubbles start flowing into the overflow tank almost immediatly after starting the car cold and the overflow tank slowly rises, this video clip shoes the bubbles after about a half hour. I started the car with a full radiator and an empty overflow tank... as you can see in the vid that its almost up to the full line buy that time.

Bubbly Overflow Tank Video

Took a flyover video of the whole engine, you can hear the radiator fan kick in seconds after this second video starts.

Engine Overview Video

Let me know what you think!

 

very clean engine....

my sh** is unbelievebly dirty. and its the same engine!

 

Thanks .

Can someone have a look at my last post and let me know where the bleeder is that Rodimus Prime is talking about?

 

sounds to me like that radiator is plugged up and not flowing properly.Also have you had that system pressure tested???. It can still cool on the highway becasue you still have all that air rushing over the rad AND the engine itself...I just looked to and you used STOP LEAK and coolant instead of water ???? BAD combo...those stop leaks are supposed to be run with water only, not antifreeze

 

Read some more of the thread Mac, I have a brand new radiator in there. The stopleak thing was a long time ago, and I did not use it with antifreeze, and only used 1/3 of the contents of the bottle. Months after the stop leak was used I had none of these problems I have today. And flushed the cooling system withing the same week that I did the stopleak. I'm hoping to get some feedback about the exhaust fumes I'm smelling bubling out of the radiator/overflow tank. Am also hoping someone can tell me where the bleeder is that Roddimus is talking about... see previous posts in this thread.

 

Sheesh.... the more I work on this the more I worry about the VERY strong smell that is comming out of the boiling over overflow tank. It smells very strongly of raw fuel or exaust. I had a couple people come smell it and it is DEFINATLY not a normal/good smell. I've smelled boiling over cars many times and this is not the smell. I went ahead and pressure tested all of the heads one more time and again... no leaking pressure. The test I'm talking about involves taking out a spark plug and screwing in a tube hooked to a pressure guage. You then turn the engine over a few times with the starter to pressureize the chamber. Pressure did not drop on any of the cylindars. But exhaust or some other foreign gass is getting into the coolent system somehow, and causing the air bubble symptoms that Roddimus is talking about. I could not find a bleeder valve on this model by the way. Could there be a crack in one of the exhaust ports in the engine that allow exhaust gasses to flow into the coolent system that would cause these issues I've been having? Macdaddy.... I got the coolent system pressure tested and it tested OK. The radiator cap is new... and definatly holds the pressure in there. Its the lever type... and it only lets stuff get into the overflow tank when the pressure goes over its max setting. At any time while running the car if I pull up on the cap lever a huge blast of gasses escapes into the overflow tank. Help!!

 

bleeder is also the stock CTS (coolant temp sensor)

 

Thanks Roddimus.
Here's how it went down this morning.

I went out to the garage and unplugged the sensor so that I could loosen it when the time came. Got in the car to start it and it wouldnt... just turned over and over (guess the sensor needs to be connected for the car to run). But what I noticed when I was turning it over to start it was that the overflow tank was bubbling... this is on a totally cold engine. So just to test that more I didnt plug the CTS back in for a bit and turned the car over some more just holding the starter on, and HUGE bubbles started to garble up like crazy out of the over flow tank, much more so than when the car is running on its own. So there's a bit of a clue for ya, doesn't sound too good does it. There is defintaly not a blown/cracked head gasket like I first thought... although everything seams to scream thats the problem.

Anyway Roddimus, I plugged the CTS wires back in and the car started up, pulled the wire and it died. Plugged the wire in and started the car again, and this time used a open wrench to loosten the CTS, till fluid/gases started coming out. The gasses never stopped. It never became a pure coolent stream. Kept adding coolent during the test to keep the engine from overheating. The gas bubbles never stopped after about 8 min of this and coolent runnining down my driveway and down the street gutter. So I tightened the CTS back in.

Couple other notes:

Reading info in other places I did the following.

To test coolant circulation I tested the heater which works perfectly... the heater will not work properly if coolent is not circulating, it will blow cold.

To test if exhaust is in the coolant (if exhaust is in the coolant, coolant will be in the exhaust) so I went to the back of the car and checked the exhaust pipe.... which had a continual light flow of white suds (like soapy water) coming down the pipe non stop for so far a half hour (still running out in the garage).

Click here to download 3mb exhaust video.

Not lookin good is it.... what advice do you have?

 

I couldn't look at the video, but the only puzzle piece that doesn't fit is the good compression readings. Check the compression with the the cooling system empty, with caps off and drain ***** open.

Bubbly cold water with enough pressure to get past the pressure cap,
smokey exhaust bubbles in the water,
foamy effluent in the tailpipe... I just can't see anything else it could be but the head.

 

I'm thinking head too..sounds BAD

 

What about a crack somewhere outside the cylindar, between an exhaust port and a coolant port? I tested the pressure in the heads pretty extensivly especially the second most recent time. I left the pressure guage on each head for at least 10 min at full pressure and they did not drop in the slightest bit. The cylindar compression was well within the appropriate range for each head... even toward upper range. Had the cap off the radiator during the cylindar pressure tests. Does a crack in an exhaust port make any sense? I have to make damn sure its a head before I do all that work. I think I'll slit my wrists if I do the heads and be in the same boat when I'm done (or worse becuase I screwed up the job). Thanks you guys for the last few posts! I think we are finnally getting pretty close to the problem. I will do the pressure tests again if you really feel I should. I wish I could somehow capture the bubble smell for you guys to have a wiff at. I just cant afford a smell-o-scope right now.