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Old 10-08-2009, 02:43 AM   #1
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Default Blown headgasket?

I'm having some trouble with my car and thought I'd run it by you guys before I go tearing into it. If you've got any ideas or suggestions it would be greatly appreciated.

I was out driving my '90 Miata today. My coolant reroute works amazing while driving, but at idle the radiator doesn't seem to get much water flow and it tends to heat up. I got caught in some traffic and temps got considerably warmer than I was comfortable with, around 240 by the time I got through the traffic (I know, I know), once I jumped on the highway temps were coming back down and I thought I'd survived. Suddenly they started going back up really quick. At that point I pulled over and called a tow truck.

Once I got home I checked the oil; looked fine. Checked the coolant; WAYYY low. I added half a gallon of water. Checked compression: 160, 140, 140, 160. I cranked the car and it ran beautifully. Drove around the neighborhood and it's losing water through the overflow tank. I let it cool cranked it in the garage with the radiator cap off and it's got a steady stream of water coming out of the radiator.

I'm assuming there's some air blowing into the coolant causing it to overflow and then over heat, but I keep trying to rationalize how it could be the thermostat or something else simple. Anything obvious I'm missing here or do I need to just go ahead and start pulling the head?
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Old 10-08-2009, 03:01 AM   #2
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probly the HG yeah man atleast i would hope it is. The low compression points to that but the water consumption leads to believe its failing somewhere in the head. The lack of coolant in the oil disputes that though lol but yeah you have work to do.
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Old 10-08-2009, 03:51 AM   #3
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Quote:
Originally Posted by pdexta View Post
I'm having some trouble with my car and thought I'd run it by you guys before I go tearing into it. If you've got any ideas or suggestions it would be greatly appreciated.

I was out driving my '90 Miata today. My coolant reroute works amazing while driving, but at idle the radiator doesn't seem to get much water flow and it tends to heat up. I got caught in some traffic and temps got considerably warmer than I was comfortable with, around 240 by the time I got through the traffic (I know, I know), once I jumped on the highway temps were coming back down and I thought I'd survived. Suddenly they started going back up really quick. At that point I pulled over and called a tow truck.

Once I got home I checked the oil; looked fine. Checked the coolant; WAYYY low. I added half a gallon of water. Checked compression: 160, 140, 140, 160. I cranked the car and it ran beautifully. Drove around the neighborhood and it's losing water through the overflow tank. I let it cool cranked it in the garage with the radiator cap off and it's got a steady stream of water coming out of the radiator.

I'm assuming there's some air blowing into the coolant causing it to overflow and then over heat, but I keep trying to rationalize how it could be the thermostat or something else simple. Anything obvious I'm missing here or do I need to just go ahead and start pulling the head?
Have you properly "burped" the cooling system? Use an OEM thermostat? Made sure all of your re-route hoses and fittings are tight and free of kinks? Don't jump the gun so soon on the HG, probably an oversight somewhere and likely your own fault(speaking from experience).
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Old 10-08-2009, 04:25 AM   #4
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The reroute I made for my Lemons car is ran around the intake and it sat about level with the radiator. I had some issues with it at first than after pushing it lower and burping it, it ran just fine. I would now rule out HG, but I would make sure the reroute is working 1st.
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Old 10-08-2009, 04:38 AM   #5
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When referring to burping the cooling system, do you mean crank it up with the radiator cap off and let it run until it gets all the air out of the system? The last time I cranked it up I did take the cap off. The car ran for 3-4 minutes with a steady flow of coolant overflowing from the cap (probably a quart in that time), which certainly doesn't seem like a good sign.

The thermostat I'm using looks like:


I've been running the coolant reroute for a couple thousand miles now and I haven't had any leaks, so I think everything is tight. I will double check for kinks in the hose, there's a tight turn on the back of the block that could be an issue. Thanks for the input.
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Old 10-08-2009, 09:42 AM   #6
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Have we verified that the radiator cap itself isn't the problem? If it's venting into the catch tank at too low a pressure, then that'll produce exactly the symptoms you describe.
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Old 10-08-2009, 10:05 AM   #7
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+1

All symptoms point to a bad cap. You may have done other damage due to overheating...but you were losing water in the first place...which caused a gradual overheat. Once it gets too low it will shoot up fast like you saw on the highway.

I killed my Integra after replacing waterpump (previous failure), head gasket and thermostat because I forgot to replace the original (Japanese characters on it) radiator cap. It leaked slowly until there wasn't even enough coolant to run past the temp sensor. I could tell the car was overheating...but the gauge never went up too far since it was only reading the air temp above the coolant level. Much like a Miata...you only get to deck the head on those once.
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Old 10-08-2009, 10:09 AM   #8
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Burping is best done with the nose of the car as high as possible(with a good reroute, not as necessary), a constant flow out of the radiator(especially with pure water) can be caused by steam being generated at an air pocket trapped in the engine.
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Old 10-08-2009, 10:14 AM   #9
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Quote:
Originally Posted by olderguy View Post
Burping is best done with the nose of the car as high as possible(with a good reroute, not as necessary), a constant flow out of the radiator(especially with pure water) can be caused by steam being generated at an air pocket trapped in the engine.
yes...start the car, put the nose in the air, and squeeze the hoses to pump the air out. My VWs were really, really bad about this.
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Old 10-08-2009, 12:04 PM   #10
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Test the cap. Find someone with the pressure tool w/little gauge(i.e. radiator shop or general repair mechanic).

Burping can be tough with some reroutes. If the outlet at the back of the head is higher than any part of the line returning to the radiator, the air may become trapped. Bear in mind, if you jack up the front of the car and you don't have a way to burp the front of the head you have done nothing constructive. The air would be trapped inside the front end of the head. You actually may have to burp at the back of the head (PITA) if that is the highest point leaving the head. This could probably be done by slightly loosening a sensor or hose back there while it is running.

Then look at the HG. I have seen a blown head gasket that only pressurized the cooling system under boost and transferred no water to oil or oil to water. It put so much pressure into the cooling system that it buckled the top aluminum tank on the radiator. The cap sending relief to the overflow couldn't keep up with the pressure rise. The car still ran 11.2 in the quarter that run and idled and ran fine out of boost.

If you need a hand, I'd be willing to help, just not this weekend.
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Old 10-08-2009, 09:37 PM   #11
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Thanks again for the input guys. Last night before posting I drained the coolant and oil, after reading the thread I decided to give it another try. I put the coolant back in, put half the oil back in... stopped... put the drain plug back in, went and bought more oil, put the oil in again and swapped radiator cap from my NB. I tried it with the radiator cap on and off, it still pissed into the overflow tank/on the floor as soon the car cranked. I boiled the thermostat in a pan on the stove (you can tell I'm single, ha) and it opened just fine.

At that point I went forward with pulling the head. Everything looks pretty good to me, but I really have no idea what I'm looking for. If you have any pic requests (of the motor/head/gasket) let me know and I'll take them. Any advice is greatly appreciated.











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Old 10-08-2009, 09:59 PM   #12
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Hmm...

Hard to say for sure, but in the third shot, the #2 and 3 pistons do look a tad too clean to me. Is that just an optical illusion?
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Old 10-08-2009, 10:08 PM   #13
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#2 and 3 do look cleaner. Did you even notice smoke from the exhaust.
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Old 10-08-2009, 10:37 PM   #14
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On the bottom picture of the head gasket, the lower side looks like there was movement, as though that side was not pulled down well against the block. Could be a warped head, or if it was replaced at one time the head and block were not cleaned well or it was torqued incorrectly.
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Old 10-08-2009, 10:49 PM   #15
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I think it's just an optical illusion. I took another pic from directly above so you can see a little better. There is a clean spot between the exhaust valves on piston #3 though.





It didn't smoke at all when it was dying.
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Old 10-09-2009, 01:48 AM   #16
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damn pdexta..... it was once so together so to speak hope u get it figured out soon...
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Old 10-09-2009, 02:39 AM   #17
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Man your pistons look clean. Mine looked like someone used them to wipe.

GL pdex

EDIT: You probably already know this, but in case you don't, make sure you blow out the oil/water in the bolt holes before reinstallation. It looks like you have some in there. From what I understand if the fluid isn't cleaned out, it can expand and potentially lead to cracks.

Last edited by Cococarbine3; 10-09-2009 at 03:16 AM.
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Old 10-09-2009, 11:24 AM   #18
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When headgaskets go bad they don't always fail the same way. It may have been weak enough to allow the powerful combustion charge (hundreds of psi) to push by, but not so open yet as to allow the twelve pounds of coolant pressure to pass coolant into the cylinder. If you kept running it with a leaky gasket it would eventually erode the gasket material and cause coolant intrusion into the cylinder(s).

I haz seed this wit bof my own eyez b4.

Good luck.
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Old 10-09-2009, 09:03 PM   #19
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Need better pics of the gasket.
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Old 10-10-2009, 02:16 AM   #20
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Yeah im with OG on this one check the head for true, and the block if you can. And barring that it would seem like an improper install didnt seat the HG properly. You obviusly didnt drive the car long enough to do much damage to it but eventualy it could have fucked up just like kotomile said.
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