Engine How common are blown head gaskets on a stock 5.0?

91GTstroked

5 Year Member
Jun 14, 2007
391
179
63
Hey guys,

My new to me car is a bone stock 93 5.0 with 27,500 miles on it.

A little background. The previous owner said he overfilled the overflow tank and some was pouring out of it once the car got up to operating temperature. The following day I decided to open the radiator cap to check the fluid. The engine was completely cold and I had pressure at the cap. Fluid was pouring out. I removed some fluid from both the radiator and overflow tank. I also replaced the radiator cap.
The car does have a bad original water pump that needs replacement.

Fast forward to today. I had a local repair shop next door to my shop check some things over on it for a second opinion. The previous owner definitely used the red coolant for some reason. The whole system is getting a flush with green coolant going back in. Also the repair shop couldn't get the operating temp over 170*. Probably replacing the thermostat as well, maybe it has a 160*?. Also they said the upper radiator hose was hot, but felt like air pockets inside of it.

The plan is to do a compression test for sure just to "hopefully" rule out a bad head gasket. It still might have the original spark plugs.

I haven't driven the car much at all. Starts up fine, and idles perfect.

So how common are bad head gaskets on these cars?

Sorry for the long post!
 
  • Sponsors(?)


90sickfox

Wasn't a pretty sight...and I've got big hands
SN Certified Technician
Mar 2, 2015
6,278
5,391
203
44
Blown head gaskets are common for various reasons. If they run hot enough they will blow. Several things don't add up to a blown headgaskrt on your car. The main one is that they can't get the temp above 170. A car with a blown head gasket will run hot.

These cars are hard for an average mechanic to bleed the air out of the cooling system. Vacuum filling it is the easiest way to make sure there's no air in the system.
 
  • Like
Reactions: 1 users

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
38,665
14,576
224
Massachusetts
20 years ago, when all my buddies had 5.0's, they were mostly stock and every once in a while someone would pop a head gasket. I've probably helped replace 5-6 sets of HG's on stock 5.0's back in the late 90' and early 2000's.

I don't recall the causes for it though, but the usual suspects were overheating, or smelling gas/oil in the radiator or losing coolant.

Running at 170? I wouldn't necessarily think HG although i'd do a compression test to check. Install a stock motorcraft 192* tstat and burp the cooling system and see how it behaves then
 
  • Agree
  • Like
  • Useful
Reactions: 2 users

2GT's

Member
Oct 6, 2021
6
4
13
71
85338
Easiest way to rule out a blown head gasket is to do a test for exhaust gas in the coolent. NAPA sells the kit for around $35 and you can do several cars with the test kit.
 
  • Like
Reactions: 1 user

2GT's

Member
Oct 6, 2021
6
4
13
71
85338
I have a 65 GT. no oil in water, no water in oil. compression within 4 pounds all around. Headgaskets 10 miles ago after "ace" mechanic diagnosed bad gasket. Blows water like old faithful. Runs strong but has combustion gas in rad. Best guess is cracked head and no time to tear it down
 

2GT's

Member
Oct 6, 2021
6
4
13
71
85338
Forgot to add the engine will idle all day and stay cool. Drive it normally at 30 mph for 7 or 8 min in AZ 90 weather and old faithful shows up.
 

manicmechanic007

Mustang Master
Sep 26, 2017
1,557
441
93
62
91GTstroked,
You sure found a nice example
I would say head gaskets are common to fail on all cars
Subaru and BMW are the worst for premature failure IMHO
Your post from the 7th means you replaced the gaskets and all is well?
If not start with a new 192 (195) thermostat and a new radiator cap and retest
Your stat is stuck open is why the 170
If you go racing the coolant will boil over
So at least the shop did not flog the crap out of your new to you Mustang
 
  • Like
Reactions: 1 users

91GTstroked

5 Year Member
Jun 14, 2007
391
179
63
Update:

I appreciate all the help everyone. Sounds like the head gaskets are just fine! Hopefully have the car back soon.
 
  • Like
Reactions: 1 users

revhead347

Apparently my ex-husband made that mistake.
15 Year Member
Jun 14, 2004
9,046
1,618
214
42
Acworth, GA
Easiest way to rule out a blown head gasket is to do a test for exhaust gas in the coolent. NAPA sells the kit for around $35 and you can do several cars with the test kit.
Autozone rents it for free, including the test fluid. Crazy they do it, but they do.

Kurt
 

chrlsful

Active Member
Mar 6, 2021
198
28
38
Lawrence Swamp, S.Amherst, MA
"...and old faithful shows up..."
if not here's a ck list I use for "coolant sys. tune up & dx":
There are abt a doz things U can wrk with to effect running temps. The big one - proper tune.
Here's the areas:
  • leaks in system; air in system
  • correct shroud (fan 1/2 in/1/2 out unless 'flex', that = 3/4 in)
  • coolant - mix, additives, age, cleanliness;
  • water pump - operation, condition; cavitation;
  • heater core - leaks, condition, it’s fan on/off;
  • block - water passages;
  • hoses - collapse, leaks;
  • thermostat - condition, temp rating;
  • radiator (sz, # rows, clean?, construction, materials - I like ol style copper)
  • radiator cap - pressure rating, condition, design;
  • fan (blades, design, clutch)
  • flush system last yr. or 2?
Too cool (below 180*F) can B a problem too. So what is the actual problem? One or several of the above? If not pukin out - it's in ur mind as it is not "overheating"
Last prt NOT 4 U 91GT but some who get excited its over 212*
 

90sickfox

Wasn't a pretty sight...and I've got big hands
SN Certified Technician
Mar 2, 2015
6,278
5,391
203
44
The red coolant is usually RV coolant. I forgot that old trick from way back when. It has a higher boiling point and is more stable when sitting for months. Some even say they transfer heat better. RVs are always under a load for extended times on the highway and are parked a lot. It doesn't mess up anything. It's probably Peak Final Charge phosphate free coolant.

Screenshot_20211218-003918_Chrome.jpg
 
Last edited:
  • Like
Reactions: 1 user

91GTstroked

5 Year Member
Jun 14, 2007
391
179
63
The red coolant is usually RV coolant. I forgot that old trick from way back when. It has a higher boiling point and is more stable when sitting for months. Some even say they transfer heat better. RVs are always under a load for extended times on the highway and are parked a lot. It doesn't mess up anything. It's probably Peak Final Charge phosphate free coolant.

Screenshot_20211218-003918_Chrome.jpg
Yeah some said to stick with the red coolant, but I'm going back to the green stuff.
 
  • Like
Reactions: 1 users

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
22,759
8,255
203
polk county florida
I think GM (brand x) used red coolant, needed changing often, Caterpillar used red also,
I'd rather pee in my radiator than use brand x red coolant,
 
  • Like
  • Wow
Reactions: 1 users

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
6,876
2,776
194
Kearney, NE
I think GM (brand x) used red coolant, needed changing often, Caterpillar used red also,
I'd rather pee in my radiator than use brand x red coolant,
If you have enough alcohol in your system for that to work as antifreeze, I doubt you can hit the radiator full neck without making a mess.

Did my Yamaha SHO engine use the red stuff? I still have some around from some car, and I doubt it was the ex’s Grand Am.

@91GTstroked, be sure to flush the heck out of the system when changing or fixing the mix.
 
  • Like
Reactions: 1 users

91GTstroked

5 Year Member
Jun 14, 2007
391
179
63
"...Could the red in the coolant be rust?..."
rust will look brownish, thru the glass will have grains/sediment/murky.
That red is honest (realy) R E D.
It could be a mix of the two. Shop said it's definitely got the red coolant.
If you have enough alcohol in your system for that to work as antifreeze, I doubt you can hit the radiator full neck without making a mess.

Did my Yamaha SHO engine use the red stuff? I still have some around from some car, and I doubt it was the ex’s Grand Am.

@91GTstroked, be sure to flush the heck out of the system when changing or fixing the mix.
Definitely will be getting flushed out.
 

chrlsful

Active Member
Mar 6, 2021
198
28
38
Lawrence Swamp, S.Amherst, MA
"...The red coolant is usually RV coolant...."
yes, in the sales container it's pink. THAT is NOT for the radiator. It is for the boat or RV's domestic water / toliet / water pipes...to prevent a frez'n burst.
 
  • Sad
Reactions: 1 user