This post pertains to a 2004 SS with the 3800 Series II at 318,000 miles. Son reported slight rise in operating temp back in June & confirmed low coolant level. Radiator had been serviced a couple of months prior. After topping off and refilling reservoir everything was fine until September when the scenario repeated while he was traveling. Topped off system and limped back home. Just as he arrived the temp shot up and a river of coolant flowed from underneath.


This is not the tensioner elbows or water pump. Leak appears to be from the rear of engine on firewall side. There is absolutely no water visible on top of the engine, thermostat housing is not leaking, heater hoses appear intact. There does not appear to be any water in the oil, all spark plugs are a nice chocolate brown color with no obvious signs of water. Car started normally and ran smooth when loading and unloading it from trailer when I rescued it a couple of weeks ago. This is not a drip, it's like a garden hose running.


Anybody have a direction they could point me in? I've already tore down the top side, saw a few curious things in the process, but nothing like I expected with the LIM.

 

Get your hands on a Cooling System Pressure Tester.

Let it stop leaking and dry.
Baby Powder or Corn Starch coat areas suspected for leaks.

Fill the System and conduct Pressure Test.
Inspect the entire Plant with a bright light beam.

 

What have you taken off? The heads? My guess would be either a leak on one of the heater core lines(maybe the heater core itself), the alternator bracket, upper or lower intake gasket, throttle body gasket, or the head gasket. Confirm your source of the leak, these things like to leak and drip, or pour, in funny places in my experience.

 

If the coolant is from the back and coming from a small port on the firewall, sounds like a heater core blew. But get a pressure tester and inspect it to be certain.

 

Hopefully not, but possibly a "Freeze (AKA..."Frost or Expansion") Plug" blew out. I believe there are 4 of them, two on each side of the engine (firewall and radiator sides). This happened to the previous owner of the project '00 SS I'm working on now.

Link....L36 freeze plug? : Other 3800 powered cars

 

RickCoMatic, thanks for the input. Unfortunately I don't think pressure testing will work with the LIM & other parts removed already. I didn't think quick enough before the teardown.

 

The_Maniac, thanks for the reply. Too many parts removed already to pressure test - didn't think of it soon enough. Leak appeared to be from the engine on the firewall side, not the firewall. All heater hoses & wall were bone dry.

 

Thanks plumbob, the plugs were the first thing I thought of when I saw first hand the amount of water pouring from the engine. If there are 4 of them then I found them all still in the engine and free of corrosion holes as best I can tell. Been under the car while up on ramps and know the leak is not coming from any of them, but higher up on the rear of engine.

 

nitehawkjcb, thanks for your response. I started the basic teardown systematically out of necessity in order to get to the lower intake manifold. The tensioner pulley, water pump & adjoining elbows were not leaking (elbows were already metal from previous pump install). Every water and heater hose was intact with tight fittings on the engine, radiator & firewall. All of the wiring, sensors & fuel injectors were removed, unplugged or moved out of the way for access. Throughout all of this I found zero evidence of water leakage anywhere on top of the engine. There was no staining around the thermostat housing, though I did find the gasket not sitting perfectly in position upon removal.


Discovery #1: Having just been professionally serviced by the GM dealership for the valve cover gasket recall I found I now had mismatched covers. The left side (next to the firewall) was original while the right side was new. Apparently a fire resulting from oil leaking onto the exhaust on that side is not as dangerous as the other. Both were showing signs of leakage, the original much worse on the rear of the cover & with a perfectly rotted gasket. I decided to remove both out of curiosity & because I was pissed - mainly to check the condition of any residual oil underneath. What I found was normal looking oil, matching what I found on the dipstick as expected. I presumed at this point there probably was no head gasket failures when combined with 6 perfectly burning spark plugs showing no evidence of washing. Checked the 8 head bolts on top - all tight.


Discovery #2: Upon removal I found the throttle body so blackened I swear we've been running diesel. The air plenum was equally sooted and a bit oily. This car was getting 30 miles to the gallon - WTF? There were no signs of water leakage anywhere around the plenum.


Discovery#3: Intake manifold provided a few surprises. First, it appeared fairly clean on top except for where the 2 bolts are located on opposite corners inside the manifold - both covered in a puddle of oil. Once all of the bolts were removed I prepared for the fight to pry it off without damaging something. Didn't happen - I literally picked it straight up with zero effort. No one believes me, but I have my son as a witness. His response: "That wasn't in the videos!" I expected to find the lower side of the manifold eat up with corrosion on the firewall side thus explaining a leak. However, it's smooth and the radiator side of the manifold has holes in it where the water is not leaking. Both heads are full of crap as you would expect.


Perhaps the oily area under the rear of the left side valve cover is not just oil, but a leaking manifold gasket. I am confused as this is not the area of the manifold that is damaged. And I have never seen a gasket leak so bad the water appears to be coming from a faucet. Not sure exactly where I am going from here given the mileage.