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Old 12-13-2012, 08:41 PM   #1
mack89
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Over-pressurizing Cooling System. Head/Headgasket?

University life is keeping me from checking the forum regularly..I haven't been here for a while. I hope you guys were able to winterize your babies before weather got cold.

So, I have been trying to solve the cooling system issue, I'll try to make it short since it's a long story.

Series of problems was initially started by a cracked expansion tank. It was cracked wide open while driving on highway, overheated engine for few minutes. Needle had stayed at red-zone for minutes until I pulled over to safe area.

Few weeks after that, car started to show the symptoms of stuck-closed thermostat. Symptoms consisted of stuck-closed thermostat because 1) overheating while driving, 2) hot and tight upper hose and cold lower hose, 3) excessive steam coming out of bleeding screw when warmed up.
At first I thought the problem was caused by improperly bled system, but turns out that thermostat was completely stuck closed. I finally took it apart, and put it in the boiling water, did not move a bit. So I requested a replacement thermostat from Oreilly's, they gave me a new one.

But a new thermostat did not solve the problem. Car still overheated and showed the 3 symptoms above. I decided to put an old thermostat housing without thermostat, but my effort did not see the light. Car currently does not have thermostat, but still overheats.

That's why I was beginning to think that cylinder head or head gasket might have been blown. Shop guys thought so, too. So we performed combustion leak test, but the blue testing fluid did not turn into yellow color. I haven't performed a cylinder compression test, nor did I do leak-down test. (I can only think of those three tests for head/head gasket diagnosis..)

But I found an interesting thing today. The driver's side upper radiator was pretty hot (160F), but other parts of radiator were cold (90-100F). Could this mean that radiator is somehow clogged? It's only 2 years old, but it's possible because it's the only part I haven't checked thoroughly.


Let me summarize in few bulletin points.

**Currently, the cooling system has..
  • No leak at all. System is holding the pressure nicely.
  • Water pump, 1.5 years old, Oreilly part. Impeller is solid and not spinning freely.
  • Radiator, 2 years old, Oreilly part.
  • Radiator hoses, 2 years old, OE part. Lower is bit covered by leaked motor oil, but they both are in good shape.
  • Thermostat, new, not defective, Oreilly part. Even with the new one, car still overheats, thus the engine currently has empty housing.

**Symptoms shown so far.
  • Engine is running fine, RPM is very stable when warmed up. No milkshake oil, no white smoke coming out of exhaust, no definite signs of blown head/head gasket.
  • Engine shows symptoms of stuck-closed thermostat, though it is currently not installed in the engine.
  • Upper hose is hot and excessively pressurized(rock hard), but lower hose is just little warm(w/o thermostat).
  • Driver's side upper radiator is quite hot (160F), but driver's side lower, middle upper&lower, passenger's side upper&lower radiator are relatively cold (90-100F)
  • Combustion leak test shows there is no exhaust gas present in cooling system. Blue testing fluid does not change. (Have not done leak-down test, compression test)


According to the symptoms shown so far, do you think the head is blown? Or do you think the radiator is somehow clogged and over pressurized the system?

I know it's a such lengthy-unorganized thread, but please take a minute and lighten up my dark path ahead. I'm totally lost right now..
Thanks in advance!
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Old 12-13-2012, 09:24 PM   #2
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cracked head, or combustion pressures leaking past the headgasket.



if it pressurizes the system, ALL THE HOSES ARE HARD.


is that the case?
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Last edited by bigugly; 12-13-2012 at 09:25 PM.
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Old 12-14-2012, 12:34 AM   #3
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Originally Posted by bigugly View Post
cracked head, or combustion pressures leaking past the headgasket.

if it pressurizes the system, ALL THE HOSES ARE HARD.

is that the case?
I didn't know that fact. I only checked the upper hose, it was pretty hot and rock hard. But the lower hose wasn't, it was only little warm. I guess I got lucky!


Quote:
Originally Posted by lcoleman View Post
Having dealt with this, yes. The pressure should be even throughout the entire system, and if it was that bad, you wouldn't need a combustion test--you'd be able to smell it in the coolant.

Sounds like a clogged radiator to me. Should've bought the Behr? You can remove it and run a garden hose through it (oh, the horror) to test.
Maybe I should've bought the Behr. A friend of mine knows a radiator supplier, he gave me one for $60. Turns out it was Murray, same brand as Oreilly ones..$70 less was very tempting for a college student who just paid four figures of college tuition lol.

So, clogged 2 years old radiator seems quite impossible, especially when it's had plenty of fresh coolant and water ever since the ET blew..But I guess it really is the clogged radiator causing this mess, still wondering why though.




I'll be replacing radiator tomorrow, I'll keep it posted. Thanks guys
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Old 12-13-2012, 09:56 PM   #4
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Having dealt with this, yes. The pressure should be even throughout the entire system, and if it was that bad, you wouldn't need a combustion test--you'd be able to smell it in the coolant.

Sounds like a clogged radiator to me. Should've bought the Behr? You can remove it and run a garden hose through it (oh, the horror) to test.
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Old 12-14-2012, 07:22 AM   #5
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Get that Behr radiator and Wahler thermostat.
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Old 12-15-2012, 12:49 PM   #6
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Well, did replace the radiator with Behr one, thermostat seemed to be in good working order, so I didn't really bother to buy Wahler one.

After replacing radiator, I performed a good bleeding procedure for 15-20 minutes. I let the engine running til the air doesn't come out of the bleeding port, seemed to be bled properly. Heater wasn't blowing hot air and there wasn't any water in heater hose, so I unhooked the heater hose from heater valve and blew several short burst of air with an air blower gun. Good amount of trapped air came out through expansion tank, heater is working fine now.

Nevertheless, problem still exists. Upper hose is hard and hot, lower hose is hard and cool. Meaning that thermostat is working fine..
After 10 minutes of test driving, coolant overflows, then overheats while idling. Both fans are doing their job brilliantly, as lower hose and lower part of radiator are very cool.

Judging by the evidence of good amount of trapped air in heater system, do you think the air is still trapped in water jacket?
Or since the car is not showing any evidence of cracked/blown head/HG, should I suspect a warped cylinder head? It seems extremely hard to believe, because as far as I know, engine block and HG blows first before the head gets warped almost every time due to the excessive heat.

My next plan is to blow air through the engine block return hose, but I'm not even convinced that air could be trapped in the WATER JACKET.
oh man I really am lost.
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Old 12-15-2012, 03:56 PM   #7
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It doesn't sound like air, but a physical blockage. And no, a warped head exhibits the same symptoms as a blown head gasket (any head sealing issue does).

When you bled, did you have the heater on high? If you couldn't get air out without compressed air, I'm wondering if the heater valve itself may be stuck and blocking flow through the system somehow.
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Old 12-15-2012, 05:20 PM   #8
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You got a stuck thermostat. Replace the damn thing. You can't cheap out on stuff like this.
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Old 12-15-2012, 09:57 PM   #9
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Thanks for your attention again, guys.

Quote:
Originally Posted by lcoleman View Post
It doesn't sound like air, but a physical blockage. And no, a warped head exhibits the same symptoms as a blown head gasket (any head sealing issue does).

When you bled, did you have the heater on high? If you couldn't get air out without compressed air, I'm wondering if the heater valve itself may be stuck and blocking flow through the system somehow.
That's what I thought..Car's not exhibiting any symptoms of blown HG/block. I was thinking that maybe the white residue on every part of cooling system has somehow interrupted cooling capability, caused overheat. So, what is that white residue on cooling system, anyway?

Oh and yeah, bleeding procedure was done while heater was on full blast, which didn't really help. So, are you suspecting that the water already in the heater system gets overflowed through the expansion tank, because of malfunctioning heater valve interrupting the flow? Maybe it's possible when it gets stuck after allowing good amount of water to enter the heater system, and then prohibiting it from fully circulating. (I don't know if that makes perfect sense, hope you understand my poor English.)


Quote:
Originally Posted by bigugly View Post
You got a stuck thermostat. Replace the damn thing. You can't cheap out on stuff like this.
That's what I had suspected at the first time way before I replaced the radiator. Putting a new one didn't really help, so I put an empty thermostat housing, which didn't help either.
Judging by the exhibited contrasting evidence of stuck-closed thermostat (i.e. cool, but hard lower hose-The weather was fairly cool today, so I assumed it should be cool and hard. Did I get this right?-, no overheat upon acceleration/driving, etc), do you think I have a faulty T-stat again? Air bubbles were coming off the center of thermostat housing when I put it in the hot water(not boiling, but hot enough), thus I thought it's safe to install.
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Old 12-15-2012, 10:07 PM   #10
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Quote:
Originally Posted by mack89 View Post
TI was thinking that maybe the white residue on every part of cooling system has somehow interrupted cooling capability, caused overheat. So, what is that white residue on cooling system, anyway?
This is the first I've seen you mention of this. Where exactly is it?

Quote:
Oh and yeah, bleeding procedure was done while heater was on full blast, which didn't really help. So, are you suspecting that the water already in the heater system gets overflowed through the expansion tank, because of malfunctioning heater valve interrupting the flow? Maybe it's possible when it gets stuck after allowing good amount of water to enter the heater system, and then prohibiting it from fully circulating. (I don't know if that makes perfect sense, hope you understand my poor English.)
Your English is exceptional, don't worry. I think the heater valve may be directly in the flow of coolant regardless of whether the heater is on or not, thus a blockage would cause a problem with the actual cooling capacity of the engine. I'm not positive about this, just a random guess.
Quote:
That's what I had suspected at the first time way before I replaced the radiator. Putting a new one didn't really help, so I put an empty thermostat housing, which didn't help either.
If the thermostat was the problem, that would've fixed it.
Quote:
Judging by the exhibited contrasting evidence of stuck-closed thermostat (i.e. cool, but hard lower hose-The weather was fairly cool today, so I assumed it should be cool and hard. Did I get this right?)
Hoses should always eventually reach operating temperature, and thus should always be pretty hard after a good drive.

Quote:
Air bubbles were coming off the center of thermostat housing when I put it in the hot water(not boiling, but hot enough), thus I thought it's safe to install.
Air bubbles don't really mean anything. If you put it in boiling water (not just hot) water, it should move from "closed" to "open."
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Old 12-16-2012, 01:30 AM   #11
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Quote:
Originally Posted by lcoleman View Post
If the thermostat was the problem, that would've fixed it.
no, it would have NOT.



gutted thermostat is almost as bad as a stuck closed thermostat. fluid isnt slowed down enough to transfer heat = overheat symptoms continue.
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Old 12-16-2012, 09:36 AM   #12
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I've never seen that happen.
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Old 12-16-2012, 11:57 AM   #13
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dont know what to tell you buddy-
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Old 12-16-2012, 02:14 PM   #14
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I've never seen that happen.
That's because it has no basis in reality - rate of heat transfer is linearly proportional to flow rate... basic physics here
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Old 12-16-2012, 02:23 PM   #15
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That's because it has no basis in reality - rate of heat transfer is linearly proportional to flow rate... basic physics here
state all the fun stuff you want- when you work on them for a living- and have done it for over 10 years, i assure you my reality and experience beats your theory.
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Old 12-16-2012, 03:00 PM   #16
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It's certainly possible for the water to flow too quickly for it to absorb enough heat, but I don't think you're going to get that with a gutted therm. My e30 and several other cars don't over heat with the thermostat out, they run cold as one would expect. Never done an e46, can't imagine it has that substantial of a water pump though.
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Old 12-16-2012, 03:09 PM   #17
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yup- thermostats are there for more than just one reason- open when hot its got to slow the water down and also close when too cool
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Old 12-17-2012, 06:17 AM   #18
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Originally Posted by lcoleman View Post
It's certainly possible for the water to flow too quickly for it to absorb enough heat, but I don't think you're going to get that with a gutted therm. My e30 and several other cars don't over heat with the thermostat out, they run cold as one would expect. Never done an e46, can't imagine it has that substantial of a water pump though.
No, that's not how this stuff works. Increased flow rate will increase heat transfer except in very rare cases. It will keep the difference in temperature between the object being cooled and the water at a higher value. It's as simple as that. You don't have to give water time to "absorb" heat. Take this from the guy who built a model of a pressurized water reactor which is very similar to our cooling system.

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Old 12-17-2012, 08:02 AM   #19
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:smh: take it from me, the guy who works on them for a living. not from models, not from theory.


you let the water go too quickly- it gets ALL of the water at the same temperature, no heat is shed off in the radiator- it overheats. im done arguing with people who dont realize experience and SEEING IT beats theory and ideas.
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Old 12-17-2012, 08:18 AM   #20
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you let the water go too quickly- it gets ALL of the water at the same temperature, no heat is shed off in the radiator- it overheats. im done arguing with people who dont realize experience and SEEING IT beats theory and ideas.
No. The water will absorb heat no matter how fast it's flowing in a system like this. There's a reason cars with stuck open thermostats often never reach operating temperature - flow rate is too high and therefore the fluid transfers too much heat. As flow increases more and more, the system will remove as much energy from the system as the radiator is capable of dissipating.

If when working on a car there was ever a time when the temp was stable with a certain amount of fluid flow and then increased/overheated when you increased the flow, I promise you there was another variable you don't account for.

I also guarantee that BMW used this very same "theory" to design the cooling system, and used many other "theories" to make the engine work as well as it does. Outright dismissing the physics that makes design of these cars possible is silly.
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