Has This Head Gasket Failed? - Problems - MX5Nutz Forum

Jump to content

These ads only show for users who are not registered or logged in


Photo

Has This Head Gasket Failed?

Head Gasket Overheat

  • Please log in to reply
11 replies to this topic

#1 Whoops330

Whoops330

    One post wonder

  • New Members
  • 5 posts
  • Location:Oxfordshire

Posted 09 May 2020 - 06:38 PM

Hi all

My son bought a 1999 MX5 NB and we've been working on it together. I'm not sure we know what we're doing, but it's been fun learning together.

About a couple of months ago a hose split and the car overheated pretty badly. He eventually got the car towed home by the AA. The car no longer starts and the AA man though he could smell exhaust fumes through the radiator.

We've eventually got around to looking at it this week. Firstly we did a compression test with the following results:

 

First 50 49 28 49 

Final 60 52 37 52 

Wet 69 62 42 62

 

Not good eh? We then stripped it back to check the timing belt and all seems ok there. Today we got the head off and here's where we need some help. I expected the gasket to be in bits but it's not. It's one of those multi layer types. The only thing is that the layers are coming apart in places - does this mean it failed? I'm guessing it must have because it looks like there's small amounts of water in the cylinders along with some rust build up where it's been sitting since it happened. I did remove the spark plugs before we stripped it back but they seemed dry. The pistons don't look too bad to me but as I say, I'm not sure I know what I'm doing (or looking for). There are some scratches just below the camshaft on the inlet side and one of the (coolant?) holes seems slightly odd; although this could be a deliberate part of the manufacturing process. Pictures are below. The block seems pretty flat to me, although one of the head bolt holes has a bit sticking out (see the photo as I'm not sure I'm describing this particularly well).

Can we just clean everything up, put new gaskets on and reassemble or do we have bigger issues?

All help appreciated!

 

https://www.flickr.c...eposted-public/

https://www.flickr.c...eposted-public/

https://www.flickr.c...eposted-public/

https://www.flickr.c...eposted-public/

https://www.flickr.c...eposted-public/

https://www.flickr.c...eposted-public/

https://www.flickr.c...eposted-public/

https://www.flickr.c...eposted-public/

 


  • 0

#2 Zed.

Zed.

    layabout

  • Members
  • PipPipPipPipPipPip
  • 1443 posts
  • Gender:Male
  • Location:Swansea, WALES.

Posted 09 May 2020 - 07:03 PM

 

Hi all

My son bought a 1999 MX5 NB and we've been working on it together. I'm not sure we know what we're doing, but it's been fun learning together.

About a couple of months ago a hose split and the car overheated pretty badly. He eventually got the car towed home by the AA. The car no longer starts and the AA man though he could smell exhaust fumes through the radiator.

We've eventually got around to looking at it this week. Firstly we did a compression test with the following results:

 

First 50 49 28 49 

Final 60 52 37 52 

Wet 69 62 42 62

 

Not good eh? We then stripped it back to check the timing belt and all seems ok there. Today we got the head off and here's where we need some help. I expected the gasket to be in bits but it's not. It's one of those multi layer types. The only thing is that the layers are coming apart in places - does this mean it failed? mls gaskets re just that, 'multi Layer Shim' construction, compressed when installed & headbolts tightened. diferent to the older graphite & 'fire-ring' construction of old

 

I'm guessing it must have because it looks like there's small amounts of water in the cylinders along with some rust build up where it's been sitting since it happened.would you have completely drained the coolant before lifting the cylinderhead?

 

I did remove the spark plugs before we stripped it back but they seemed dry. @ top of chamber so  should be dry unless the cylinder was full of water / coolant

 

The pistons don't look too bad to me but as I say, I'm not sure I know what I'm doing (or looking for). its the cylinder bores & the sides of the pistons / piston rings that matter, although you cannot see much of them while installed....

 

There are some scratches just below the camshaft on the inlet side and one of the (coolant?) holes seems slightly odd;normal

 

The block seems pretty flat to me, although one of the head bolt holes has a bit sticking out Alignment dowel. should be another @ front on same side

 

Can we just clean everything up, put new gaskets on and reassemble or do we have bigger issues?

 

whats the cylinderhead gasket face look like?

Aluminium is more likely to warp & distort in an overheat situation than a cast iron cylinderblock :confused: 

Rich.


  • 0

50 Shades of Silver. '91 NA6CE, Not a show car :driving: 
Ohlins dampers, COP conversion, 4.778:1 & more ideas than time :yes:
Bodger :ph34r:

https://mighty5s.com...silver-na-eunos


#3 Whoops330

Whoops330

    One post wonder

  • New Members
  • 5 posts
  • Location:Oxfordshire

Posted 09 May 2020 - 07:37 PM

Thanks Rich

Can these MLS gaskets fail without any visible 'break' to the gasket?

We removed the radiator and drained what we could, although I suppose there could've been some coolant left in the system.

The cylinder head gasket face look OK as well, although we left the inlet manifold attached so perhaps I need to give it a better look over. It didn't seem warped with the naked eye but I guess we're talking millimetres for an issue.

Do you think the overheat (white smoke, the lot) caused the issue? Has the gasket gone, hence the low compression and no start?

Finally, do I take a risk and replace the gasket in the hope that'll fix it or take the head for pressure testing and/or repair (any recommendations - I'm in Oxfordshire)?

Thanks again.


  • 0

#4 Jim A

Jim A

    Made a start

  • New Members +
  • Pip
  • 47 posts
  • Gender:Male
  • Location:Northern California

Posted 09 May 2020 - 08:24 PM

Head gaskets fail when an overheat causes the head to warp.  A proper mechanics straightedge and some feeler gauges will tell you how much.  It’s unlikely that a simple head gasket replacement will result in a satisfactory repair.  Very unlikely.

 

There are limits of warpage acceptable before the warpage needs correction and the sealing surface re-machining.  By warpage correction, I mean that the head needs to be unwarped, in an oven, with the proper jigs, by someone who knows what they’re doing.  Only after it’s been unwarped should the sealing surface be machined.  If the head is machined flat without unwarping first, the cam boreS will no longer be aligned, which can and usually does destroy the cam bearings.

 

Even if you do the head right, a severe overheat will often de-tension the piston rings, so keep that in mind also.


  • 0

#5 dadbif

dadbif

    Nutz regular

  • Members
  • PipPipPipPip
  • 678 posts
  • Location:UK

Posted 09 May 2020 - 09:15 PM

Check the head with a proper straight edge and a .0015 feeler, same on the block, if it’s ok slap a new gasket on and stop worrying....
If the head is badly warped get it skimmed, or find another.
  • 0

#6 Jim A

Jim A

    Made a start

  • New Members +
  • Pip
  • 47 posts
  • Gender:Male
  • Location:Northern California

Posted 09 May 2020 - 09:50 PM

My ‘95 Mazda factory service manual says that the maximum allowable distortion is 0.004”, when measured across six planes.  If it’s less than four thousandths the factory says it’s good to go.

 

If distortion is greater than 0.004”, Mazda says to grind it a maximum of 0.004”.

 

If it’s way beyond maximum allowable tolerance, it should be replaced or straightened. Here’s a video of one owner who had to straighten a Toyota Supra head, and subsequent videos follow her progress through completion:

 

https://www.youtube....h?v=HZYa3LmiNiY

 

If good heads are readily available it’s often cheaper to replace it with a known good head.  If not, a competent machinist can make it as good or better than new.

 

Skipping to the end, and bypassing the two videos between, here’s the results of her cylinder head straightening:

 

https://www.youtube....ap&index=5&t=0s

 

and...

 

https://www.youtube....h?v=cfdJyfMU6Uw


  • 0

#7 Whoops330

Whoops330

    One post wonder

  • New Members
  • 5 posts
  • Location:Oxfordshire

Posted 10 May 2020 - 11:48 AM

Thanks all. Does anyone know of any decent machine shops near Banbury?

I'm going to check the measurements as accurately as I can tomorrow.


  • 0

#8 Whoops330

Whoops330

    One post wonder

  • New Members
  • 5 posts
  • Location:Oxfordshire

Posted 15 May 2020 - 01:46 PM

The machine shop has the engine, It's distorted 1/16 of an inch. They'll check for cracks on Monday.


  • 0

#9 dadbif

dadbif

    Nutz regular

  • Members
  • PipPipPipPip
  • 678 posts
  • Location:UK

Posted 15 May 2020 - 02:56 PM

.060” fucking hell!! Did you run over it with a tank?
  • 0

#10 Whoops330

Whoops330

    One post wonder

  • New Members
  • 5 posts
  • Location:Oxfordshire

Posted 15 May 2020 - 04:08 PM

Sorry, 16 thousands of an inch! 


  • 0

#11 dadbif

dadbif

    Nutz regular

  • Members
  • PipPipPipPip
  • 678 posts
  • Location:UK

Posted 15 May 2020 - 04:36 PM

That’s better, is see you said the same to our colonial cousins..
  • 0

#12 Zed.

Zed.

    layabout

  • Members
  • PipPipPipPipPipPip
  • 1443 posts
  • Gender:Male
  • Location:Swansea, WALES.

Posted 15 May 2020 - 04:57 PM

The machine shop has the engine, It's distorted 1/16 of an inch. They'll check for cracks on Monday.

WTF??? :o

.060” fucking hell!! Did you run over it with a tank?

:blink:

Sorry, 16 thousands of an inch! 

:lol:

That’s better, is see you said the same to our colonial cousins..

+1....

nearly commented :whistle: 

 

anyway,

0.016" (3/8mm) is not too bad, probably flatten out when they clamp it before machining :yes: 
and same when you bolt it down onto the block :thumb-up:

 

it'll be fine :driving:

Rich.


  • 0

50 Shades of Silver. '91 NA6CE, Not a show car :driving: 
Ohlins dampers, COP conversion, 4.778:1 & more ideas than time :yes:
Bodger :ph34r:

https://mighty5s.com...silver-na-eunos






Also tagged with one or more of these keywords: Head, Gasket, Overheat

1 user(s) are reading this topic

0 members, 1 guests, 0 anonymous users