• Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech

Compression Test/Coolant Leak

  • Thread starter Thread starter RangerJoe
  • Start date Start date Feb 27, 2011

RangerJoe

I leave the horn on while driving
15 Year Member
Apr 26, 2010
2,560
1,146
184
Georgia
Feb 27, 2011
#1
  • Feb 27, 2011
  • #1
Ok, here is a long post. Just built new 331 stroker. Block was decked and heads were milled .015 for clean up (iron gt40). Compression is about 10.15:1. Edelbrock Performer Intake.

Motor has not been broken in yet. It has been cranked up about 5 or 6 times, ran for a total of probably 20-25 minutes trying to work out idle and such so it could be driven. Noticed small puddles at exhaust pipes, watched for a little while and realized that it was more than condensation. Pulled upper intake, it looked like I was dripping antifreeze into the end cylinders. Pulled intake, re-installed, bigger puddles. Went back, redid gaskets with red gasket maker around coolant ports, changed oil. I haven't tried to restart it yet and see if it still leaks.

I ran a compression test on the cylinders and a compression test on the coolant system. I pumped the coolant system up to 16#. After about 20 minutes it falls about 1#. I don't see coolant in the intake runners (I have the upper intake off at the moment). I have found a few leaks in hoses, etc, been fixing them as I go.

My compression test are crappy. I can't get more than about 25# on any cylinder with the dry test, and with the wet test I get about 50#. Is this normal? I know the rings are not set to the bore walls yet, but would it let this much by?

Intake is torqued to 25# in the "proper" sequence. I did compression test with plugs out of heads.

Any ideas?

Thanks
 

RangerJoe

I leave the horn on while driving
15 Year Member
Apr 26, 2010
2,560
1,146
184
Georgia
Mar 1, 2011
#2
  • Mar 1, 2011
  • #2
Update

Well, I hoped that I would have recieved some replies to my post. I did figure out what was wrong...it wasn't the car. I guess ingnorance falls to me. I had never actually done a compression test before, so I didn't realize that you had to use the starter. I was turning the motor over by hand with a wrench. Come to find out, that doesn't work. So compression is fine. I thought I would update this post in case someone else came across it in a search.

Thanks to any who took the time to read it.
 

ID89GT

10 Year Member
May 26, 2008
1,659
18
49
Spokane Valley, WA
Mar 1, 2011
#3
  • Mar 1, 2011
  • #3
Glad you figured it out lol
 

LarsD

Founding Member
Jul 2, 2002
2,680
119
123
Texas
Mar 1, 2011
#4
  • Mar 1, 2011
  • #4
I would have answered if I had an idea of what your problem was. Ever get all the coolant leaks fixed?
 

RangerJoe

I leave the horn on while driving
15 Year Member
Apr 26, 2010
2,560
1,146
184
Georgia
Mar 2, 2011
#5
  • Mar 2, 2011
  • #5
I've been working, so I haven't had time to put upper back on and crank it up. However, when I did the cooling system test, I wasn't seeing any coolant in the intake runners. So that is a good sign. I had to torque the lower intake about 8 times before my torque wrench began to click as soon as I turned it. It seemed like everytime I went to torque it, I could get about an 1/8 to a 1/4 of a turn before it clicked. I guess I just didn't let the gaskets compress the first two times. I am going to go over them again with torque wrench before firing it up again. I found a few post where guys were having to torque over and over again before finally reaching correct torque. Hopefully this works!
 
B

BYRDPE

Founding Member
Nov 4, 1998
1,556
0
37
Memphis,Tn.
Mar 3, 2011
#6
  • Mar 3, 2011
  • #6
RangerJoe said:
I've been working, so I haven't had time to put upper back on and crank it up. However, when I did the cooling system test, I wasn't seeing any coolant in the intake runners. So that is a good sign. I had to torque the lower intake about 8 times before my torque wrench began to click as soon as I turned it. It seemed like everytime I went to torque it, I could get about an 1/8 to a 1/4 of a turn before it clicked. I guess I just didn't let the gaskets compress the first two times. I am going to go over them again with torque wrench before firing it up again. I found a few post where guys were having to torque over and over again before finally reaching correct torque. Hopefully this works!
Click to expand...
this is how i torque my lower also. i actually retorqued it numerous times over a 2 hour lunch break time span. by doing it this way i do not have to remove the upper and retorque.
 
You must log in or register to reply here.

Similar threads

P
Engine Mysterious coolant leak at back of engine
  • palerider94
  • Jan 18, 2026
  • Fox 5.0 Mustang Tech
Replies
1
Views
162
Fox 5.0 Mustang Tech Jan 19, 2026
AeroCoupe
X
Engine 5.0 Head Gaskets installed wrong block coolant passages???
  • Xam Sirrah
  • Jul 21, 2025
  • Fox 5.0 Mustang Tech
Replies
12
Views
583
Fox 5.0 Mustang Tech Dec 22, 2025
Qtrhrse23
Q
Engine 87 NA - Tune or no Tune needed?
  • R82148V
  • Sep 17, 2025
  • Fox 5.0 Mustang Tech
Replies
8
Views
314
Fox 5.0 Mustang Tech Sep 17, 2025
R82148V
Engine 1990 LX 5.0L EFI Mustang Fuel Management Problems - HELP!
  • 5.0LXStanger
  • May 25, 2025
  • Fox 5.0 Mustang Tech
  • 2 3
Replies
45
Views
2K
Fox 5.0 Mustang Tech Jul 11, 2025
5.0LXStanger
L
Engine Need help diagnosing 2 dead cylinders
  • lvgnmz
  • Feb 13, 2025
  • Fox 5.0 Mustang Tech
Replies
3
Views
413
Fox 5.0 Mustang Tech Feb 13, 2025
Mustang5L5
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?