Coolant Leak 1999 5.7

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.

OR VietVet

Multnomah Falls
Supporting Member
Military
Joined
Oct 8, 2014
Posts
19,261
Reaction score
31,735
Location
Willamette Valley
Haven’t had one break in the intake during removal, but I’m sure that’d be worth a few dozen cuss words. Mine usually just end up leaking from inside the fitting where the end of the hose meets and overflowing a bit of coolant.
When I dealt with them breaking, was when I was not prepping correctly. Lots of corrosion built up there and I did not let soak in PB Blaster. I was in a hurry and should not have been. The Lisle tool would have been nice to have, that @the 18th letter shows.
 
Last edited:
OP
OP
M

Modoyadney

Member
Joined
Jan 26, 2023
Posts
36
Reaction score
47
Location
Germany
I took a closer look on it again today. Everything around the intake and the heater hoses looked and felt dry.
It is just a little wet between the head and block.

I dried it off with some brake clean and a towel and check again after driving tomorrow.
If it gets worse, I might try a bottle of the stop leak that has been recommended.

Thanks for your help. I'll keep you updated. :thumbsup:
 

Capn Jack

TYF Newbie
Joined
Dec 23, 2022
Posts
1
Reaction score
3
I had a similar heater hose connection leak issue around 200k on my 94 burb. I replaced the fitting in the intake with the GMC part (metal construction) and never looked back. Still dry at 385k. Several overheating episodes over the years lead to sucking coolant wound that I couldn’t cure. In the end I replaced the engine with a new crate one.
 
OP
OP
M

Modoyadney

Member
Joined
Jan 26, 2023
Posts
36
Reaction score
47
Location
Germany
After quite a while I have had finally time again, to take a closer look this this again.
I found one leak at the coolant reservior. This could be easily fixed by cutting a small piece of the hose and installing a new hose clamp.

Unfortunately this was not the leak that leads to the coolant dripping off the transmission bell housing.
If I also have a case of the infamous intake manifold leak, where exactly should I see the coolant comming out on the rear of the engine?
 

exp500

Full Access Member
Joined
May 14, 2017
Posts
1,789
Reaction score
1,618
Small leaks that travel or evaporate are sometimes tough to find. Some toilet paper or even paper towel will soak it right up after wrapping, if paper is stained or destroyed you have found it.
One of the worst for me was rear heat tee leaking under pressure spraying on exhaust manifold.
 

Eman85

Full Access Member
Joined
Apr 18, 2021
Posts
377
Reaction score
555
A flex head mirror and a good small flashlight are essential. Look at the back corners of the intake where the intake meets the head. It will not be easy as it's a long way back there. You'll need something to stand on and probably will end up laying across the motor, just be careful not to lean on anything breakable.
 
OP
OP
M

Modoyadney

Member
Joined
Jan 26, 2023
Posts
36
Reaction score
47
Location
Germany
I came to the conclusion, that there is definitely a waterleak between the cylinder head and engine block on the passenger side. I'm not sure if there something wrong with the intake manifold gasket, didn't find anything here.
I could take a look in one of the cylinders on the passenger side with a endoscope and found no sign of water coming into the cylinder. Additionally I have made a test with one of those CO2 head gasket leak testers - also negative.

Is this a thing that the head gasket only leaks coolant outside the engine?

Bought a bottle of Bar's liquid copper now and give it a try. If that doesn't help, I guess I'll have to repalce the head gasket and that also includes repalceing the intake manifold gaskets ...
 

Hoesgottaeat2

Full Access Member
Joined
Dec 7, 2022
Posts
631
Reaction score
1,843
Location
Western NY
I came to the conclusion, that there is definitely a waterleak between the cylinder head and engine block on the passenger side. I'm not sure if there something wrong with the intake manifold gasket, didn't find anything here.
I could take a look in one of the cylinders on the passenger side with a endoscope and found no sign of water coming into the cylinder. Additionally I have made a test with one of those CO2 head gasket leak testers - also negative.

Is this a thing that the head gasket only leaks coolant outside the engine?

Bought a bottle of Bar's liquid copper now and give it a try. If that doesn't help, I guess I'll have to repalce the head gasket and that also includes repalceing the intake manifold gaskets ...

Follow the directions to a tee. I drain about a gallon out of the radiator, pour the solution in, start it and then top the radiator off with leftover antifreeze/coolant I drained out. Whatever antifreeze/coolant won’t go back in the radiator I pour into the overflow tank.
Then take it for a 15-20 minute drive to circulate.
Watch it over the next few days and top off as necessary.

Please circle back and let us know how you make out.
 

Forum statistics

Threads
129,239
Posts
1,812,628
Members
92,339
Latest member
Thekenstar
Top