Thread: 2008 Grand Prix 3.8 III Series Coolant leak

So, I was pointed over here from Reddit and have read a bunch of threads about possible fixes but with variations of the motor and differences in configurations I thought I'd see if there is anything that I'm missing.

2008 GP 3.8 III Series started overheating a couple of weeks ago. I've had the car for about a year (has 140k miles) and the heater has never worked, which I should have looked into when I got the car it seems. Gauge went into the red a couple of times and I pulled over right as the engine failsafe kicked in and got the car home once it was cool enough to limp a mile at a time.

Once home I replaced the thermostat and water pump, flushed the coolant (ignored the heater elbows because they were metal and the leak was obviously coming from the water pump), bleed the air out and everything seemed good. Drove around town for 4 days without any issue. Then it started over heating again after about 10 miles of driving. Pulled over to the side of the freeway (yeah, I thought it was that fixed) and eventually made it home without driving in the red.

Decided at that point to replace the LIM gasket. Didn't want to, but I did it (didn't use RTV though). Put in a new thermostat and flushed the coolant again and refilled it. Waiting for operating temp to bleed the air out and I notice it's leaking bad. Dumping out passenger side in front of the engine. Turn the engine off and hear hissing and a spray that stops before I can get around to the side to see where. Dripping continues with the engine off and I pour more coolant in to see if it'll drip and it does.

So, last night I buy new heater elbows, figuring that there's nothing else it could be. Replace those after work today, refill the coolant and I'm not getting a drip with the engine off. Put the new thermostat in and start the engine. Seems fine for a minute or two and then I notice the leak is going again. Dripping pretty stead down the front of the engine off of a bolt that is directly in the middle of the crank shaft and a/c pullys. Which tells me it's higher than that but I can't get a good look or a good picture.

Tonight I read for the first time about sealing the water pump bolts, but I was watching coolant drip out at a steady stream, "drip" isn't even a good word for it but "pour" seems a little extreme. I also read for the first time about the timing cover issue which sounds like a lot more work than I want to do at this point. I mean, I'll do it if that is where all signs are pointing but I won't be happy about it. So far I'm a few hundred into this and every day off I've had for two weeks. I don't have money to burn and have spent more than I want to, but I know I've spent less than I would have at a shop for pretty much anything I've done so far.

Help please!!

I would unfortunately wager money that it's the timing cover. Not a fun job and takes a bit of work to do. Cleaning old gasket material and correctly sealing oil pan with rtv is one of the hardest parts, but the worst is when people don't prime the pumps upon removal of the timing cover. I'd check to see if re- priming is needed and if so pack with Vaseline (I know, sounds crazy, but machinists of over 30+ years experience do this and I have for two successful rebuilds of this engine).

I would check to see if your heater core is restricted as this can cause the gasket to blow.

Mine did this because some idiot mixed dex and green together!

Good luck!

That's as good as I could get. I'll try again tomorrow. It was dark when I ended for the night.

Originally Posted by wstefan20

I would unfortunately wager money that it's the timing cover. Not a fun job and takes a bit of work to do. Cleaning old gasket material and correctly sealing oil pan with rtv is one of the hardest parts, but the worst is when people don't prime the pumps upon removal of the timing cover. I'd check to see if re- priming is needed and if so pack with Vaseline (I know, sounds crazy, but machinists of over 30+ years experience do this and I have for two successful rebuilds of this engine).

I would check to see if your heater core is restricted as this can cause the gasket to blow.

Mine did this because some idiot mixed dex and green together!

Good luck!

I'm thinking the heater core is good because when I first thought I had it fixed it was blowing hot air like a champ, which had me pretty confident that I had done a perfect job.

Forgive my ignorance but I'm not sure what you mean by "prime the pump" when it comes to this. I'm used to the idea of putting a little bit of fuel in a chamber prior to trying to start an engine after being dry, but I don't get what you mean here or why Vaseline would be used or where it would be used at.

Originally Posted by Scottydoggs

how far up is it wet? almost to the top of the cover? being the block is wet it looks like gasket failure so far.

I think it's wet to right below the water pump. I'll double check again in the morning. I was pretty sure I finally had it figured out before I replaced the elbows that I didn't take pics today.

When you say "gasket" do you mean the timing cover gasket or the LIM one again?

Another fact that might be helpful: my oil seems to be clean. I thought I was getting a little steam out of the dipstick tube when it first overheated, but that might have just been from the engine since the oil has not appeared milky at all.

I agree with Scotty. If the timing cover gasket is leaking where I think it is, there would be no mixing of oil and water so just because your oil is clear does not mean you are out of the blue. It might be worth trying Scotty's advice of sealing the threads and heads of the water pump bolts. MAKE SURE you actually have a correct torque wrench when re-tightening them. I'm a big fan of the felpro water pump and timing cover gasket btw. Helps with the bolt seal leakage issue too.

Sorry about the confusion of priming the oil pump. I was remembering when I removed the oil pump, which might be a worthwhile "while you're in there" thing to do since it requires removal of the timing cover anyhow. I'd also replace the crankshaft main seal since it usually comes in the felpro kit anyways at most auto part stores. Just make sure you clean everything very well and use good rtv along the pan. What I was referring to is if you remove the oil pump for inspection, unlike the old pumps that can be spun with a drill to "suck up" or prime the oil (get rid of air that would cause pump to cavitate and not suck up oil), ours have to have some help. Your choices on this are either to remove the oil pump cover and pack it (literally just smear it in there) with petroleum jelly, and replace cover, or to remove the oil sender sensor and find a barb fitting that will fit and attach fitting with hose running to funnel and then use the starter (with coil pack and pump relay disconnected) to spin the engine to work up oil pressure. I've used both ways, but found the first is much easier and works well. Don't worry about the jelly, it melts within seconds and is harmless and will come out with your next oil change.

personally, having rebuilt these engine's from scratch, I really wouldn't recommend this. It obviously can work, but you 1. Run the risk of the pump cavitating (won't suck oil because there's air trapped) and 2. Running your bearings dry for a moment, which you usually can't hear or see, and won't cause issues immediately but could cause issues down the road and premature bearing wear.

The saying "better safe than sorry" comes into play, and for a few minutes of time and $1 Of Vaseline, there's really no reason not to.

There's a reason that factories, machine shops, and mechanics all do this.

Again not saying it's mandatory, just highly advised. If you don't remove your pump cover, then there should be enough left in there.

I agree with you if he does not remove the oil filter or pump cover, but I've seen first hand the affect of the pump cavatating and spinning bearings.

Again, the importance goes up the more oil is removed, everyone has their opinions and mine is better safe than sorry!

New pictures after taking the water pump off. Figured I'd share these to see if anything new presents itself before I replace the timing chain gasket.
Above water pump.

Inside water pump/timing chain cover connection.

Originally Posted by wstefan20

I agree with you if he does not remove the oil filter or pump cover, but I've seen first hand the affect of the pump cavatating and spinning bearings.

Again, the importance goes up the more oil is removed, everyone has their opinions and mine is better safe than sorry!

I think I'm going to skip the oil filter and pump cover on this adventure. I'd just as soon keep the complications to a minimum.