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Old 06-17-2012, 11:03 PM   #1
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Default Compression in coolant

Alright I got a question. I seem to be getting a lot of bubbles/overflowing when my radiator cap is off and the car is at idle. Is it normal for the car to be overflowing coolant at idle? If so how much overflow is acceptable?

Basically my temp gauges have been throwing me off. I have had 2 mechanical AutoMeter gauges read my coolant temp at around 200-210F at idle but my VDO electric gauge reads maxed out at 250F. I figured I had air in the system so today I jacked up the front end and started to burp the system.

Well at idle my coolant seems to just overflow. Around 210 (when my fan kicks on) it overflows a lot then shoots back down like it had lost the air. I would fill it up again and it would do the same exact thing. I did this for quite some time until I decided to hold my idle up a bit, around 2000rpms. Well holding it there would make my coolant shoot out of the radiator like a volcano after a few moments. To me this seems like I am getting compression in my cooling system like a bad head gasket or a cracked head/block.

What do you guys think? My head gasket looks alright. It is a 3 layer gasket so I know it could be leaking in between and not noticeable. Also my head shows signs of my new valve seals leaking so that explains my white smoke on cold starts. I figure I have one of the three blown or cracked. Not quite sure where to go from here, I am clueless.
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Old 06-17-2012, 11:19 PM   #2
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do a compression and/or leak down test if you think you're leaking it out through the head gasket
also - are you talking about having the cap off of the top of the rad? while you're idling and doing all this when you say it's over flowing
or are you just talking about it moving in and out of the overflow tank?
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Old 06-17-2012, 11:22 PM   #3
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Quote:
Originally Posted by cpolly69 View Post
do a compression and/or leak down test if you think you're leaking it out through the head gasket
also - are you talking about having the cap off of the top of the rad? while you're idling and doing all this when you say it's over flowing
or are you just talking about it moving in and out of the overflow tank?
Last time I checked compression it was great, 200s in all cylinders
Leak down test failed because it kept shooting coolant into the tester (even when I drained the radiator a bit) It would bubble for a bit then you could see the coolant shoot into the tester - fail

Yes the cap off the radiator at idle
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Old 06-17-2012, 11:32 PM   #4
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if you haven't done a test recently - i'd say do one again
i know oil could make a basic compression test look good sometimes when it really isn't - that's why it's recommended that you add a teaspoon after doing the test to see if the numbers change
i'm not sure if water/antifreeze could do the same thing
but if you're putting compressed air into the cylinder and you're getting antifreeze back into the tester from that - that's definitely not a good sign
that adding oil step can help point you in the right direction - if it has no effect on the compression number it's usually a sign that it's valve guide stem seals or head gasket...
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Old 06-17-2012, 11:40 PM   #5
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Quote:
Originally Posted by cpolly69 View Post
if you haven't done a test recently - i'd say do one again
i know oil could make a basic compression test look good sometimes when it really isn't - that's why it's recommended that you add a teaspoon after doing the test to see if the numbers change
i'm not sure if water/antifreeze could do the same thing
but if you're putting compressed air into the cylinder and you're getting antifreeze back into the tester from that - that's definitely not a good sign
that adding oil step can help point you in the right direction - if it has no effect on the compression number it's usually a sign that it's valve guide stem seals or head gasket...
I wasn't putting compressed air into the cylinders, the car was at idle when I did my test.

But it's to late for anymore tests, here are some pictures and I will give details


When I loosed up my manifold to remove the head I had noticed coolant/oil run from under the #1 side. Pics are shitty but #1 cylinder looks cleaner than the rest and that usually indicates coolant in the cylinder. #4 (far left) is wet because I think it got oil/coolant on it when I was turning the head over but I am not 100% sure on that


#1 piston is on the far right. I had noticed when I turned the motor over a few times that #1 and #4 cylinders had a small white ring around the walls. To me it seemed to be a mixture of coolant and oil. No signs of any cracks
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Compression in coolant-photo0261.jpg   Compression in coolant-photo0262.jpg   Compression in coolant-photo0264.jpg  
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Old 06-17-2012, 11:49 PM   #6
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I'll give you $500 for it as it sits.
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Old 06-17-2012, 11:50 PM   #7
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I'll be glad to take $500 for the head as it sits. Car don't sit, she squats now with my new coilovers lol
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Old 06-17-2012, 11:53 PM   #8
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If you're building a new engine, why do you care about any of this ----? If you want to just turn wrenches, I'll pay for your fuel and beer to get to my apartment, I have a list of things you can do to my turbo car while I supervise/berate.
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Old 06-17-2012, 11:56 PM   #9
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If you're building a new engine, why do you care about any of this ----? If you want to just turn wrenches, I'll pay for your fuel and beer to get to my apartment, I have a list of things you can do to my turbo car while I supervise/berate.
Built engine is coming if this one is hurt. I plan to build another engine anyways as a backup but I will keep this one in as long as I can.

And it's my daily, not looking forward to driving my 12mpg truck again
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Old 06-18-2012, 11:32 AM   #10
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Some reading for you...

How to check a head for warp
https://www.miataturbo.net/showthrea...636#post855636

How an aluminum head is pressure tested for cracks.
https://www.miataturbo.net/engine-performance-56/how-aluminum-head-pressure-tested-cracks-64549/

Why not to let your head be belt surfaced/sanded
https://www.miataturbo.net/engine-performance-56/why-not-let-your-head-belt-surfaced-64394/

How to Clean a Head Gasket Surface
https://www.miataturbo.net/showthrea...665#post862665

How to resurface an Aluminum Head For a MLS head gasket.
https://www.miataturbo.net/showthrea...818#post863818

Head Gasket Repair
How to Clean the block surface
Pistons installed.
https://www.miataturbo.net/engine-performance-56/head-gasket-repair-how-clean-block-surface-w-pistons-installed-65074/
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Old 06-18-2012, 08:29 PM   #11
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What head gaskets are recommended? I can get an aftermarket from my machinist pretty reasonable, but same quality that mine was so afraid it will just crap out again.
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Old 06-18-2012, 10:49 PM   #12
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Fel-Pro
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Old 06-18-2012, 10:52 PM   #13
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Are they MLS? Mine was MLS, I don't quite remember the brand but they are out of Dallas just some big auto parts place
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Old 06-19-2012, 11:16 AM   #14
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Spend a few extra bucks for the name, big name parts have some sort of R&D department.

The china gaskets are clones. Not bad for most other gaskets to use, but the HG needs to be good.

Fel-pro
Victor-Renz
Cometic
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Old 06-19-2012, 11:28 AM   #15
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The multi layer steel (MLS) gaskets from Mazda or Fel-Pro are what are commonly used by most here, even with turbos.
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Old 06-19-2012, 04:18 PM   #16
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I think napa sells a gasket for around 50 bucks that they said is just a repackage of the OEM mazda headgasket. Forgot what brand, but they were selling a felpro for 69 or 79. I compared the cheaper one to my mazda one and it was exactly the same. Rivets in the exact same spots with the same number stamped. I had one from an ebay set too, and it had 4 rivets instead of 2. Made me weary of using the ebay HG
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Old 06-19-2012, 08:23 PM   #17
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I got a Fel-Pro for $50 from my parts guy. New hoses/clamps, im doing it all.

The head checked out fine, 1 valve guide was a tad loose but nothing to be concerned about. Not warped in any way, no valves leak, seems to be good to go. Rechecking my block for cracks and installing the head tomorrow after I get my parts.
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Old 06-22-2012, 09:15 PM   #18
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Alright finally got the car back together.

According to 3 gauges I idle at 200-210F. My stock cluster gauge reads under halfway and my 2 autometers read right around the 200-210 mark. My VDO electrical reads around 250, I know it's not right because the Autometer gauges are in the same spot my electrical is and according to my dads temp gun it reads 200ish.

What is a better way to get idle cooling? I don't like 210 temps I know I can get cooler than that. Any ideas?
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Old 06-23-2012, 12:34 AM   #19
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wetter water
lower temp thermostat
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Old 06-23-2012, 12:35 AM   #20
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no thermostat, and I have always had problems with water wetter foaming in my dirt track car, has anyone else had it foam?
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