Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

3800 S3 slow coolant leak... where to?

My 2006 Lacrosse (3.8 series 3 with 150k miles) has a slow coolant leak that I can’t seem to place. I have to add a splash (probably under a half cup) just once every couple of weeks to keep the recovery tank on full. Here’s the story:

I bought it a year and a half ago, and I don’t think it used any then. A year ago, with the suggestion of this community, I cleaned my throttle body (has coolant running through it). I reused the gasket, since I didn’t have time to special order one. I think this is when it started leaking, but I’m not positive. Over the past year, I’d guess I’ve put in 2-3 quarts or less. A month or two ago, I tore back into the throttle body, to replace the gasket in hopes that it was the culprit. It was in bad shape and melted. I replaced it with a new Fel-Pro gasket and put it back together. It still is using the same amount (maybe 1/4 inch on the reservoir per 2 weeks or so.) I also changed the coolant, replaced the reservoir, and replaced the radiator cap. I also pressure tested the cooling system, with “normal” results- drop of a couple PSI over 20-30 minutes.

The three things I think it might be are:

  1. Intake manifold gasket (some say that the Series 3 fixed the problem, some disagree)- there is no coolant that I can see in the oil fill and just a bit of what seems to be normal condensation/emulsion from short trip driving. No “milkshake”.

  2. “Coolant elbows” under alternator- I can’t see a leak there but it’s hard to see in that area. These are apparently a common problem.

  3. Throttle body mounting gasket (again)- torque specs are 89 in-lbs. I bought a torque wrench that had in-lbs but it was really just a foot-lbs one that had markings for in-lbs. It was inaccurate and didn’t even go that low. So I just snugged the bolts up.

Any thoughts? I’d like to get this sorted out, and I appreciate your help!

Have you put your car on jackstands and crawled under there yet?

You might at least see signs of crusty dried coolant, which would point you to the leak. Might be something as simple as a crusty water pump, hose, radiator, etc. It’s also a good idea to CAREFULLY look at things while the engine is idling. Perhaps the leak is more obvious with the engine running

I’d do what I mentioned first, before worrying about #1 and #2 just yet

No crusty areas that I can see. It doesn’t leave any spots on the garage floor, either.

89 inch pounds is about 7 1/5 ft lb that is not very tight but it is more than"snugged up".

I googled “10 ft lbs” and read some posts on that. I’d guess I got it in the ballpark, if not tighter than that.

It is not “normal” to lose 2-3 pounds pressure in 20-30 minutes. I consider a cooling system to not be leaking when it’s stays pressurized overnight and doesn’t lose ANY pressure. Losing any pressure in that short of time means there’s a leak. Use a mirror and I bet you’ll see wet coolant elbows. The plastic intakes on these things are notorious for melting where the EGR passage goes through the upper intake. They’ll melt there and there’s a coolant passage to throttle body where it melts allowing coolant inside the intake.

I own 3 GM cars with that 3.8L engine. These engines are fairly bullet-proof. They’re in it for the long haul.

My vote is for the coolant elbows (2). Take a look with a flashlight. See if you’ve got the original black plastic ones.

They become brittle and crack with age and heating/cooling cycles.

You might want to try stuffing a little piece of paper towel just below the forward elbow where it leaves the head. See if gets damp with coolant.

Next, I’d vote for a weeping water pump. That’s not out of the question.

"1.Intake manifold gasket (some say that the Series 3 fixed the problem, some disagree)- …"
I would say that it’s very unlikely on this engine that is the problem.

I’ll bet it’s the elbows or a water pump. Neither replacement is a major operation. It can be done with care and hand tools in the driveway. The hardest part with the elbows is picking out the broken pieces of plastic (with o-rings) that stays in the head because these babies will crumble when you attempt to “remove” them.

I’d replace them with a kit that includes 2 aluminum elbows and O-rings that sells for about 15 bucks.

Just tried this, can only see one of them and I can’t really tell. It’s super tight in there.

It is definitely tight in there. If I recall a fluid leak from there can drip down and land on the edge of the head gasket itself. Inspect carefully and patiently and sometimes you can see a trail through dust/oil residue.

I have a cooling system pressure tester (Stant). I’ve had it for decades. It goes on the radiator neck. That device allows one to pressurize the cooling system, cold and have a look. Being cold, the coolant can’t boil away.

How about any drips on the plastic shield below the drive-belt (serpentine belt) that could indicate a water pump leak.

Oh, by the way, how come water-pump wasn’t on your suspects list?

Red Wine Time (wine:30) has started at my house, here (I drink some for the health benefits) and I’m relaxing, so I just remembered something…

I have a few mirrors that live in my tool box. One of them (about 2"x4") works well for inspecting these tight locations. Stuff it between whatever you can stuff it between, angle it at 45 degrees, shine a flashlight right into it, wiggle it around slowly, and you can illuminate an area and inspect it all at same time!

Good ideas above. If you have to add coolant, this much is clear, it’s going somewhere. External leaks – which can evaporat on hot engine and transmission parts e before hitting the ground — are sometimes easier to find by putting a dye in the coolant then using a special lamp to spot the leak. Auto parts stores usually stock that stuff. The coolant could be sucked into the engine too. Which of course wouldn’t show up as an external leak. Coolant can indeed leak into the oil, but you’ve ruled that out. But a leak of coolant into the intake manifold or cylinders can happen too. It will show up at some point by destroying the cat , among other stuff, like the EGR system. The throttle body and intake manifold gaskets are where I’d guess a coolant leak into the engine would most likely occur. A good shop should be able to tell you one way or another.

You can remove the “sight shield” (plastic beauty cover) on the engine and look at the brass coolant bleeder valve to be sure there is no evidence of a leak. These tiny valves do not need much tightening. Over-tightening that small brass needle valve will damage it.

Also, again, Why is “water pump” not on your culprits list? How’d you rule it out?

1 Like

It was at the dealer for an alignment today, I asked them to take a look. He looked it over real quick, and didn’t see anything. I think that my next step will be to remove the throttle body and replace the throttle body mounting gasket (for a third time), as based on my memory, it started leaking around when I removed it the first time. I’ll also check the water pump for crustiness. Is there any sealant I can put on that throttle body gasket? Or just put it back? I will try and find an accurate in-lb torque wrench too.

since you have a problem visually inspecting in these tight places, you might want to look at something like this:

for laughs I bought one and I was amazed how much things I can inspect now :slight_smile: