Head Gasket? - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Engine Performance This section is for discussion on all engine building related questions.
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 09-16-2009, 10:48 AM   #1
Senior Member
Thread Starter
 
Join Date: Jun 2006
Location: Orlando FL - UCF
Posts: 688
Total Cats: 1
Default Head Gasket?

So the Miata overheated about a month ago (heater hose slipped off the back of the head), and around the same time started running funny. The car runs normally, except that it doesn't want to idle and sounds...off...during decel. There is no smoke, and both the coolant and oil look fine, but cylinders 2/3's spark plugs look different than 1/4.

I did a compression test a few months ago, and got 200-205 across the board. I did another test the other night and got 203,180,180,205 which leads me to believe that I have a leak between 2 and 3, but after adding some oil down the cylinder it bumped up to 205 for both.

The only other thing that could cause my symptoms, besides the lower compression, would be a dying coilpack but I just replaced it last Feb.


(sorry for spelling/gayness, posting from my phone)
coastertrav is offline   Reply With Quote
Old 09-16-2009, 08:17 PM   #2
Elite Member
iTrader: (15)
 
Join Date: Sep 2007
Location: Incline Village, NV
Posts: 2,073
Total Cats: 5
Default

IIRC when the test rises higher after a wet test then it's the rings.

Leakdown>Compression test
thesnowboarder is offline   Reply With Quote
Old 09-17-2009, 02:36 AM   #3
Senior Member
Thread Starter
 
Join Date: Jun 2006
Location: Orlando FL - UCF
Posts: 688
Total Cats: 1
Default

Yeah, I thought the same thing, but you have to understand that the pressures between 2 and 3 were nuts on the same.

I need to try a leak down test the next time the car is running well enough to make it to the shop (and therefor air compressor). I am really, really hoping that it is not rings, because as a poor college student that would be a fairly bad thing. Also, the price on the M-tuned rods are just about right, and it would be unfortunate to get that far into the motor and leave it stock...
coastertrav is offline   Reply With Quote
Old 09-17-2009, 03:35 AM   #4
Elite Member
iTrader: (15)
 
Join Date: Sep 2007
Location: Incline Village, NV
Posts: 2,073
Total Cats: 5
Default

I hear ya, college student here building a car..
thesnowboarder is offline   Reply With Quote
Old 09-17-2009, 03:39 AM   #5
Elite Member
iTrader: (1)
 
NA6C-Guy's Avatar
 
Join Date: Feb 2008
Location: Birmingham Alabama
Posts: 8,038
Total Cats: 43
Default

Those are the same symptoms that lead me to refresh my head and throw on a new head gasket to prepare for boost. Several months later and a bunch of work thrown down the toilet, I fixed the real issue which was the rings. I was sure it was the head gasket because I had ~ 185,160,160,185. Surely those 2 middle cylinders were leaking across the head gasket... they weren't. If oil bumps up the compression, its the rings. You are correct about doing the pistons. I kick myself in the *** every time I think about how I left the stock rods in. "Oh, I'm only going to shoot for ~200whp, it will be fine" Then everyone starts dropping stock rods on the road at not much more than 200. Do the rods!!!
NA6C-Guy is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 57 07-19-2017 05:11 PM
Another Cast Manifold Corky Bell Prefabbed Turbo Kits 18 11-22-2016 10:01 PM
Bad head gasket or ? shooterschmidty Engine Performance 8 09-30-2015 11:28 PM
Another Alternator thread ihiryu General Miata Chat 9 09-28-2015 11:22 AM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 11:12 AM.