MadMattDrifts

I have a mysterious coolant leak that I can not pin point.

LC9 5.3, 4WD.

Picked up this 2007 Suburban back in August of last year. Love it so far. Everything is great, previous owner took great care of it, deleted the DOD, studded the head, new water pump, replaced pretty much everything that was serviceable. Runs great, hasn’t thrown a fit once.
I noticed that I would leave puddles of oil and coolant here and there. Oil turned out to be a loose oil filter, loose oil drain plug, and a leaky oil cooler block of gasket. No big deal, fixed everything quick.


Now the coolant leak, I immediately replaced the two coolant tee’s since I noticed one was dripping onto the ignition coil a bit and I know they are a service item since I have sold hundreds of them.
The leak is still there. I had a broken engine mount for about a month or so to where the engine would lift up quite a bit. That has been replaced with OEM parts. I was wondering if there is anything that could break from that? It seems to leak randomly, especially when it is sitting.
This morning, there were no puddles. It seems that it all runs down towards the back of the block or the leak originates from the surrounding area. I tried pressurizing the system, but not for long enough I guess. It runs all the way down to the oil pan and onto the swaybar.


My only next step is to either add dye into the system or pull the intake manifold to get a better view of the back of the engine and service everything there.
I appreciate any suggestions.
Thank you.

hanky

Did you do the cooling system pressure check when the engine was cold or warm ?
Many times a leak disappears once the engine warms up.

MadMattDrifts

I did it when it was cold.

Cusser

I've had leaks more visible AFTER the engine has been shut off for 10 minutes, that actually heats up the coolant.

repairman54

I find most leaks on a cold engine start up when the first expansion occurs. If that fails I go right to the dye test as that will find the smallest leak, even ones that show no possible sign of a leak.

MadMattDrifts

Added the dye, it all looked the same. I noticed that the backing plate of the water pump has a leak, but it was just a bunch of coolant that was gelled up. Dye did not help me find it at all since it was all over the place where I could see the coolant.

The weirdest part was that the coolant was all over the bellhousing and leaking down to the sway bar, pooling on the x member. It was running down along side the head gasket and head bolts showed the dye. My only assumption is that it somehow leaked from the pump and got blown towards the back of the engine.

Decided to replace the pump anyways, since it was a Premium Chinesium pump "JDMSPEED" and these 5.3 pumps are know to leak. Yeah, I know. Got a GMB from my work for the meantime while I order the AC Delco.

It seems that the leak is gone for now, but the cooling system has no pressure, so no knowing for sure. Doesn't over heat. I will try to keep burping it.

Will keep this updated.


Water Pump Leak

Cusser

I've had to replace the water pump on our 2005 Yukon Denali twice since we got it in 2010. Issue was leakage out the seal.

MadMattDrifts

Update:


I still don't have leaks on the ground. Coolant level hasn't changed.

Cooling system is still not building any high pressure. It's not overheating, also.
Barely any hissing when I open up the cap after a full warm up and a drive. Had the same issue on my Expedition, was never able to figure it out.

Wil keep my eye on it and take it to my buddy at the dealership to get the system bled better maybe.

MadMattDrifts

Update #64748:

Coolant level isn’t dropping. Pressure still seems low after a long drive. Can take the cap off with nothing shooting out. No overheating. I was able to get the temp gauge up higher (215-220 probably) when I had front and rear heaters on and romped on it for 15 or so minutes. I still smell coolant here and there in the engine bay. Next step is to pull the heads and replace them along with the head gaskets. It seems that the previous owner/200 pound gorilla with a wrench had no strength and left everything loose. Got a feeling the heads might come loose or it is leaking from the head studs. No loss of performance, however. Even when towing.

Haven’t seen any puddles of coolant, just saw two more dye spots on the sway bar.

Found plenty of loose oil pan bolts, however. That’s where the leak was coming from too. Tightened them down, will keep an eye on it too.

MadMattDrifts

The reason the leak has slowed down was the because the system was bot building pressure due to the coolant tank cap becoming defective right as I replaced the water pump.

Kept noticing the small drips again. Installed some Bars tablets (same as the dealer used back in the day). Installed a new cap. The leak immediately appeared after a drive and I still had a lot of dye left in the system. I did see it leaking. After another drive, it looked like the leak was slowed down a lot.

The head studs that the previous owner installed are seeping. Master GM tech at a dealer said that the Bars stop leak will seal it up. My plan is to check the torque on the studs, and if they are loose, torque them down again. Or just replace the studs with OEM head bolts.



Really tempted just to pull the heads, new OEM gaskets and seals everywhere, and use OEM head bolts. I’m not planning to boost this vehicle, so no need for head studs that will leak.