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Old 06-20-2012, 09:14 AM   #1
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Default Help me figure out what to do (bad headgasket for sure)

Hi, as some may know, I rebuilt this engine two years ago.

Somehow, the engine is was early 1989 and had 160 000 miles. So I did rings, bearings, gaskets, belts and the head was check for pressure and flatness.

Then I drove the car for about 20 000 miles with a Megasquirt standalone, RX7 injectors, BEGI turbo kit (6-7 psi), .... but, my wideband was'nt working properly, I mean, it was'nt working at all, so it was burning rich as hell.


Everything was drivable until August last summer, I had a coolant leak from the intake manifold due to loose nuts. After this, problems started to arrive, the coolant started to become darker (presence of oil I assume) and presence of coolant appeared in oil....

It was hard to get from 65mph to 75mph with foot down.
The compression was bad (from 145 to 185, can't remember which one were the baddest)
I was able to drive for 20-25 minutes in city without overheating, but as soon as I was doing highway, the coolant temp would reach out 224 fahrenheit (readed with the megasquirt), every time it happens, I had to stop on the side of the road, put the heater at maximum heat and open the hoods to help the fan cool the engine down.

(This was during warm summer day, here in Montreal, around 85-90 F)



So, I decided to pull the head off yesterday to see what was there and the prep the head for a flatness check at a machine shop.

I was surprised to see all of this carbon buildup and was expecting a clearly blown headgasket, but it seems to be "OK".


Here are the shots of what I did yesterday.


Head :



Block :




Assuming the cylinder order on a 1990 1.6L miata is like that:



Closer shots :

Cylinder 1, head side:


Cylinder 2, head side:


Cylinder 3, head side:


Cylinder 4, head side:



Cylinder 1, block side:


Cylinder 2, block side:


Cylinder 3, block side:


Cylinder 4, block side:




What I am going to do:
-Have the head prep then check for flatness
-Have to block prep for new head gaskets and clean the surface of the pisons
-New Felpro composite head gasket
-New ARP head bolt
-Now I have a working wideband that I tested lately!
-What else?



So, what else do you think I should take care of? Does this even make sense?

*note, the head gasket was an egay one.



Bonus shot (why not taking advantage of hot summer days, the longest one of the summer, time of the picture was 8:45 pm) :
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Help me figure out what to do (bad headgasket for sure)-0eabf271.jpg   Help me figure out what to do (bad headgasket for sure)-3143ad36.jpg  
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Old 06-20-2012, 09:34 AM   #2
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OEM head gasket > Fail-Pro head gasket.

If your looking to just hurry and be done, a stock rebuild for the head should be in order.

Just my .02
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Old 06-20-2012, 09:46 AM   #3
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Well, I though Felpro, Cometic and OEM where all as good...

The head was stock rebuilded last time it was pulled, I am gonna have it check first...
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Old 06-20-2012, 10:12 AM   #4
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Looks to me like you have an excessive amount of carbon buildup.
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Old 06-20-2012, 10:13 AM   #5
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That would have blown the head gasket?
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Old 06-20-2012, 10:17 AM   #6
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I've used the fel-pro hg kit twice without any issues on my nb.
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Old 06-20-2012, 11:44 AM   #7
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Looks like you been running pig rich, or you have an oil consumption issue, or just not been getting to op temp so you are not burning off the crud.

20k miles and that much build up is not good.

With that much build up in the combustion chamber, and the top of the pistons, how much is built up on the back of the valves????

Also the build up is a result of the bad drivablity, not being able to get over 65 with foot down.

First thing to do is rotate the engine so all 4 pistons are at mid stroke.

next pour about 1 inch of oil on top of the pistons, this will be a back yard way to check ring seal, let set for several hours to over night.
When you come back, you should have about the same amout of oil on top of all 4 pistons, if one or more has lost way more than the rest of them, you have a ring issue.

now lets check the head out a bit....

pull the cams from the head....

Now ...
How to Fluid test a Cylinder head
https://www.miataturbo.net/engine-performance-56/how-fluid-test-cylinder-head-65558/

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

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

Use a LONG 3/8 or 1/2 extention to check for warp, not the most accurate, but will get you close and have an idea of how bad it is.

Now lets move to the block....

I forgot to mention use blue paper towels wads to plug the oil return, and oil feed to the head.

Head Gasket Repair-How to Clean the block surface w/ pistons installed
https://www.miataturbo.net/engine-performance-56/head-gasket-repair-how-clean-block-surface-w-pistons-installed-65074/


Also 224*F coolant temps you should not be over heating...

Water boils at 212*

For every pound of pressure the rad cap holds on the coolant system you can go 3* over boiling point.

You should have a 13psi cap.... so....

13psi X 3* = 39*

so 212* + 39* = 241*

241* is boiling....

BUT if your cap is weak say holding 7psi and not 13psi.. you will boil over sooner..
same goes for any sort of leak allowing pressure to bleed off.
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Old 06-20-2012, 11:49 AM   #8
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Hi Bogus, thanks alot for the quick answer, I already readed 3/4 of what you put here, thanks alot, was very helpfull so far.

By using a long 3/8" or 1/2" extension, you mean one for a ratchet? English is not my native language, so there is some things I don't pre assume.

Last edited by absRTP; 06-20-2012 at 12:09 PM.
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Old 06-20-2012, 11:56 AM   #9
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No problem!!

Yes an extention you would use on a ratchet... a long one like 18-20 inches... so the center part will span the length of the head.
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Old 06-20-2012, 12:09 PM   #10
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And for boilling water,

My readings are in celcius,

The non-linear gauge in the car went all the way to the right, so I used the MS to read the temps, I had something like 107 Celcius up to 112 Celcius at peaks....


Which gaves us:
107C --> 224F
112C --> 233F

This is considering sea level, and water boiling at 100C (212F) and Montreal is about 185 feets over sea level, no big deal will be see about boiling point.

Other consideration, maybe a new radiator cap.


Plus, I think there is possibilities for an air pocket to have accumulate over the thermostat after the coolant from the intake manifold appear...

Somehow, trouble appeared 2-3 weeks after the said leak was repaired (intake manifold bolts were re tighten up)


Can I just block the coolant passage from the intake manifold?
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Old 06-20-2012, 12:25 PM   #11
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You could block the coolant flow thu the intake mani... But I am unsure what effects it would hold for you.

It is common to do down here in the south where it will not be as cold as you get in the winter months.

The reason the OE flow the intake is to heat the maini so it will heat the air as it passes so the fuel and keep it vaporized into the combustion chamber.

Also I do not know if it would cause "hot spots" in the block due to the coolant not flowing as it was designed to do by the facory engineers.

Unless someone who has studied the coolant system in depth speaks up and can give a reason one way or another, I would say do so at your own risk.
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Old 06-20-2012, 12:27 PM   #12
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I don't think winter would affect it, the car is stored for winter.

EDIT :

I just remember this :


https://www.miataturbo.net/showpost....9&postcount=12:
Quote:
Originally Posted by absRTP View Post
Well.... here is some updates, things were looking fine for a few days...

Restart to overheat 2 days ago, would not want to cold down even with the heater on.

Here are the symptoms:

-Rough idle all the time (worst than before)
-Coolant is now getting darker green (oils in it)
-Oil is getting dark after 400 km and less thicky (I'm sure there is water in the oil)
-Smell like oil when accelerating
-HLAs are noisier than ever, even after heat up...


I did'nt do any compression test yet, I don't have the tool, but I know I could do the crank test to see if their is bubble coming out of the radiator filler hole.

So I think my B6 is gone, now I'll have to put the hand on a fresh BP and do a +200cc swap.

Last edited by absRTP; 06-20-2012 at 12:58 PM.
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Old 06-20-2012, 01:26 PM   #13
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I'm not seeing any evidence of a blown gasket, either. Possibly a cracked block?
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Old 06-20-2012, 04:05 PM   #14
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Warped ---- from running too rich.
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Old 06-21-2012, 10:28 AM   #15
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Yesterday I did the "ghetto ring test"

How it was at 9pm yesterday :



and how it was 9 hours later (at 6am this morning)




Here is a shot where I measured the distance from the top of the block to where the fluid was after 9 hours, just to give an idea of what went throught.




So, does that means my rings are busted? or this is still accetable?



Gonna try to do the ghetto valve seals test tonight or tomorrow.

Thanks everybody
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Old 06-21-2012, 11:47 AM   #16
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What was the measurement at 9pm?

Looks like you have about a half inch worth of diffrance.
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Old 06-21-2012, 01:32 PM   #17
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I think I put about 1" of oil in every cylinder,

I did'nt measured the quantity I put into the cylinder, but, with CAD assisted programs, I was able to do some measurements,

It looks like this is what I lost:

Cyl 1: 2mm
Cyl 2: 9.5mm
Cyl 3: 2mm
Cyl 4: 4.5mm

This is not rocket science, I did it considering the bore is 78mm, I scaled everything else.

The oil viscosity was 10W30 and the air temperature (even overnight) was 80-85F
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Old 06-21-2012, 01:44 PM   #18
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Now me and the mad scientist are going to replace the piston rings you fried.
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Old 06-21-2012, 01:44 PM   #19
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You should be fine.

Rock on with the head gasket
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Old 06-21-2012, 01:49 PM   #20
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So the rings seems fine for you?

Next step, head check!
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