Head gasket, water pump, or ?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Milblazer

Full Access Member
Joined
Mar 21, 2013
Posts
268
Reaction score
5
Location
Colorado
First Name
MilBlazer
Truck Year
1984
Truck Model
K5
Engine Size
6.2
I recently did a flush on my cooling system, changed the hoses, and put in a new thermostat. The flush must have knocked some crude loose because a small leak developed. I used some stop leak and that leak stopped. Shortly after my truck started overheating according to the gauge. Swapped out that gauge with another one and it showed overheating as well. I started doing some research to see what could be wrong. I thought there could be some air still in the lines so with the radiator cap off I started it up to see if there were any bubbles. I didnt see any but I did notice that the upper radiator hose was not getting entirely hot. There were spots right near the thermostat and where the hose connects at the radiator that would get hot but the high point would only get warm. The hose would feel some what pressurized but it felt like there was no coolant running through it.

All this was with the truck leaning to the right in the street. I pulled it into the driveway so it would be leaning to the left with the radiator cap up high so any air could rise to the top. I let it run some more and noticed the upper hose still felt like it was full of air so I decided to "pump it" by squeezing and hopefully getting some air out. As I did this I noticed the coolant level fell so I thought I was making some headway. At this point I also noticed some small bubbles coming out of coolant. These bubbles were the size of bubbles from pepsi in a glass, nothing major.

I have no idea what is going on so I put the cap back on, after shutting it off. Truck was parked back in the street and I decided to look into the coolant reservoir with the radiator cap on for bubbles that would indicate a head gasket failure and did not see a single bubble. I drove it around until the temp gauge hit 210, parked it, looked in the coolant overflow tank again and still no bubbles. I'm at a loss for what I should do or check next. I have heard of a kit to test for exhaust gases in the cooling system. Also I have read that I should do a compression test on each cylinder. Any advice, comments, karma, or magic voodoo you want to throw my way so I can have a normal operating temp truck again?
 

RetroC10Sport

Supporting Member
Supporting Member
Joined
Sep 29, 2010
Posts
17,191
Reaction score
2,518
Location
Green Bastard Parts Unknown
First Name
Jay
Truck Year
2001
Truck Model
pontiac aztek
Engine Size
3.4
How hot was it getting? Most normal cooling systems will have some bubbles regardless. Also, they will go past the rating of the thermostat and when the thermostat opens, it will cool down to the usual 190*. My truck will go up to 215-220 before going back down to 190.

Usually stop leak will just make things worse. It make have causes the new thermostat to stay shut.
 

Milblazer

Full Access Member
Joined
Mar 21, 2013
Posts
268
Reaction score
5
Location
Colorado
First Name
MilBlazer
Truck Year
1984
Truck Model
K5
Engine Size
6.2
The temp gauge I had in before was a diesel gauge that maxed at 240. The hottest it got with me driving was around 230-235 I say. The temp gauge in it now is a gasser gauge that maxes at 260. I let it get halfway between 210 and 260 so about 235 on that as well. I wasnt driving across town like that, just around the neigborhood since I noticed the heating problem.

I can say it does warm up to operating temperature (fast idle kicks off) a lot sooner than it did before I did the cooling flush and stop leak.
 

82chevy350

Full Access Member
Joined
Jul 30, 2010
Posts
775
Reaction score
51
Location
Van Buren, AR
First Name
Joey
Truck Year
1982, 1976
Truck Model
C10, K10, K5
Engine Size
350, 350
Did you burp the system?
 

82chevy350

Full Access Member
Joined
Jul 30, 2010
Posts
775
Reaction score
51
Location
Van Buren, AR
First Name
Joey
Truck Year
1982, 1976
Truck Model
C10, K10, K5
Engine Size
350, 350
Let it run with radiator cap off till the thermostat opens and closes a couple times it gets all the air out of the system so you don't have air pockets.
 

ScottyB

Full Access Member
Joined
Aug 28, 2013
Posts
1,068
Reaction score
1,102
Location
Whatcom County, Washington
First Name
Scott
Truck Year
1800
Truck Model
phantom
Engine Size
2 squirrels
Drilling an 1/8" hole in the housing will let air through so it will burp better. It will also help prevent an air lock at the thermostat that may keep it from opening.
 

Milblazer

Full Access Member
Joined
Mar 21, 2013
Posts
268
Reaction score
5
Location
Colorado
First Name
MilBlazer
Truck Year
1984
Truck Model
K5
Engine Size
6.2
Well I took the thermostat out and inspected it. Looked fine to me. No blockages or buildup on it. I threw my older one back in and just started it up so fingers crossed here.
 

Milblazer

Full Access Member
Joined
Mar 21, 2013
Posts
268
Reaction score
5
Location
Colorado
First Name
MilBlazer
Truck Year
1984
Truck Model
K5
Engine Size
6.2
Did you drill it before you put it in?

No. I had spaced out the hole idea until I had already put gasket sealant and the housing on. Good news is either the burping helped or the thermostat I had in was bad. Took her for a drive down the highway at 75 and the temp needle barely went above 210. I just got back and had been driving around for about half an hour just to make sure everything was alright. It's nice when you can drive your truck out of your neighborhood and it doesn't overheat! Thanks to everyone for your help.
 

austinado16

Full Access Member
Joined
May 25, 2012
Posts
611
Reaction score
222
Location
Central Coast, CA
First Name
Todd
Truck Year
1990 w/307k miles on the clock
Truck Model
GMC V1500 Suburban SLE
Engine Size
5.7L TBI/4L60/3.42's
Did you burp the system?

Posted an answer last night, but it appears to have vanished......

To bleed a cooling system, you leave the radiator cap off, and run the engine at 1,500-ish until you have good flow through the radiator and the hoses are all hot, AND heat coming out of the heater. During this process the coolant will drop, so you'll need to top off the radiator several times. Once the system is up to normal temp and coolant is circulating, top off the radiator to the very top, put the cap back on, and add the correct level of coolant to the overflow tank.

Regarding the T-stat, you want to use the Mr. Gasket brand. Best T-stats made and will cure that situation where the temp gauge makes some ridiculous climb to 215+ before the T-stat "pops" and opens. That ain't normal!
 

Milblazer

Full Access Member
Joined
Mar 21, 2013
Posts
268
Reaction score
5
Location
Colorado
First Name
MilBlazer
Truck Year
1984
Truck Model
K5
Engine Size
6.2
Posted an answer last night, but it appears to have vanished......

To bleed a cooling system, you leave the radiator cap off, and run the engine at 1,500-ish until you have good flow through the radiator and the hoses are all hot, AND heat coming out of the heater. During this process the coolant will drop, so you'll need to top off the radiator several times. Once the system is up to normal temp and coolant is circulating, top off the radiator to the very top, put the cap back on, and add the correct level of coolant to the overflow tank.

Regarding the T-stat, you want to use the Mr. Gasket brand. Best T-stats made and will cure that situation where the temp gauge makes some ridiculous climb to 215+ before the T-stat "pops" and opens. That ain't normal!

So I'm supposed to give it a few rpms with the cap off? I tried that before and all I ended up with was with a lot of coolant bubbling out of the radiator when I let off the accelerator. I'll definitely look into the mr gasket brand of t-stats.
 

austinado16

Full Access Member
Joined
May 25, 2012
Posts
611
Reaction score
222
Location
Central Coast, CA
First Name
Todd
Truck Year
1990 w/307k miles on the clock
Truck Model
GMC V1500 Suburban SLE
Engine Size
5.7L TBI/4L60/3.42's
I always bring the rpm's up on any vehicle I'm bleeding the cooling system on. It makes the water pump spin fast, creating a nice pressure wave that forces all the air out of the block, head(s) and heater core(s).

Sometimes I have to leave the coolant level a little low in order to prevent splashing, or gurgling over as the coolant heats up and expands, etc. Then I simply top off at idle, and put the cap back on.
 

Latest posts

Forum statistics

Threads
44,411
Posts
956,922
Members
36,733
Latest member
rjshope2007
Top