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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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Discussion Starter #1
Good day folks,

I'm sure this has probably been beaten to death, but I didn't find a lot in my search that describes exactly what I'm experiencing. I have a 2004 Pontiac Bonneville GXP. Unfortunately, there were never a lot of these made but of course they share the LD8 engine with the Deville which is why I'm hoping someone may be able to help.

My car has just under 120,000km so it's pretty low mileage. There is a notable smell of coolant under the hood starting after the engine has been running about 2 minutes. I haven't noticed a leak anywhere and the coolant level hasn't changed. I've pressure tested the system with the engine cool-lukewarm. After about 30 minutes there was no change in pressure. I also tested the cap and found no problem. Regardless, I cleaned up the cap mating surfaces on the tank and installed a new OEM cap, just in case there was a contact problem.

A worthwhile point to mention is that while under warranty, the dealer replaced my water pump at least twice. In each case the smell disappeared for about six months and then returned. Soooooo.....

1. Is it possible the water pump 'O' ring was incorrectly installed and has led to premature failure? I understand these can be a little bit annoying to seat properly.
2. I've heard of possible problems with the crossover gaskets leaking but can anyone tell me if replacing these has corrected this problem with no apparent leak or change in coolant level?

It seems coincidental that the smell disappears every time the water pump is replaced. In each case new OEM parts were used. Again, I don't see anything that looks like it's weeping. I did add dye today and took the car for a drive on the highway. I'll be having a much closer look with a UV light.

I have washed the engine (I usually do this every few car washes anyway). I'm definitely not interested in any type of cooling system additive. If there's a problem, my intention is to fix it correctly.

Thoughts will be appreciated!

Thanks :)
 

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98 DeVille, 97 DeVille d'Elegance
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Probably a seep somewherd hard to see. My rear heater hoses were seeping behind below thd TB. Worm clamp was loose. Pressurize the system and I'm sure a seep will turn up. The crossover leaks can be extremely challenging to see. A couple mirrors, a good light and a few beers...
 

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Put your hand under the water pump housing/cover and see if you find coolant there. A very small leak would be enough to cause coolant smell.
 

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2010 DTS
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87,300 Posts
Obviously it is a very, very small leak (seepage). The 2000+ motors are known for crossover manifold gasket leaks. If that isn't it, or is too big of a job for such a small leak, this is one of the few times I would ever recommend a (one time) dose of sealant tabs. If you decide to use it, use Barsleaks tabs, product code HDC.

 

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2005 CTS/ 2008 DTS/ 2008 STS V8 N*/ 2011 CTS4 ALL W/D Pearl
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688 Posts
I would say crossover gaskets.

Very hard to see, try and look at the 4th crossover gasket closest to the fire wall and just above the tranny. You might just see a little bit of coolant on top of the tranny at that spot.

You could smell coolant for months before a crossover gasket gets bad enough that you would see coolant or see any sign of coolant lose from the surge tank.
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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Discussion Starter #6
Thanks for the replies everyone. I'm going to poke around next week and see if I can spot anything. I'll post an update once I have more details.
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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Discussion Starter #7
Just wondering if anyone can tell me...

If I decide to go ahead and replace the crossover gaskets, does the water pump actually have to be removed or can I take this off as an assembly? I really don't want to take it off if there's no leak. It's the third pump in 120,000 kilometres and I think it's only been 20,000 at best since the last replacement. I know from what I've read that access it tight, but I get the impression this is more because of where the wiring harness runs than the water pump itself.
 

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98 DeVille, 97 DeVille d'Elegance
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No you don't have to remove the pump or cover to get crossover out. Removing the cover probably helps with access though.
 

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2010 DTS
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I know from what I've read that access it tight, but I get the impression this is more because of where the wiring harness runs than the water pump itself.
Correct. The WP has nothing to do with the difficulty of the job. The WP is a piece of cake.
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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Discussion Starter #10
Thanks guys. I just wanted to confirm so I'll know what parts to order. I figure there's no good reason to take more apart than necessary. Once I dig into it, hopefully I'll find an actual leak and can focus on the exact problem area(s). I've got a new right cam/valve cover to install so I'll do that at the same time. The gasket has been changed numerous times and it still leaks oil. My best guess is that the dealer over tightened the bolts and warped the cover. I seem to recall this has been done twice as well.
 

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300 SRT8, 392 cubic inches of tire smoking power!
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Alumaseal is your friend.
 

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300 SRT8, 392 cubic inches of tire smoking power!
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8,193 Posts
MoistCabbage said:
I do hope you're kidding...
Better than Goldenseal IMO.
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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Discussion Starter #14
I'm hoping someone can offer a little advice...

There is a coolant line that connects to the right side of the crossover. It's difficult to see while still in the car, but I'm wondering how this disconnects? Is it a Quick-Connect fitting similar to the fuel lines? I appears that there is some sort of collar around the line that will prevent me from getting a release tool in place. I assume the collar will pull out providing for tool access but I thought I'd ask. I'm working on getting any specialized tools that I don't already have, along with the parts in order to replace the crossover gaskets.

Thanks!

 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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That's the heater coolant inlet line. The quick connect uses a snap ring nylon collar and O-ring.

www.nalleygmc.com or maybe on the HELP ! racks at large parts stores.

I just posted the entire water crossover blowup in another thread here or in Seville or Northstar - a question about gaskets and plenums.
 

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Discussion Starter #16
That's the heater coolant inlet line. The quick connect uses a snap ring nylon collar and O-ring.

www.nalleygmc.com or maybe on the HELP ! racks at large parts stores.

I just posted the entire water crossover blowup in another thread here or in Seville or Northstar - a question about gaskets and plenums.
Thank you. I'll have a look for your other post.
 

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Discussion Starter #17
I'm left with refilling the system with coolant and checking for leaks. The job was not horrible but definitely for the first time around a little time consuming. I made sure that I had all the right tools and parts up front which helped a lot. Although I haven't run the car yet, I'm confident that the problem is resolved. There was only one gasket of the four that didn't show signs of failure. The lower right port showed definite signs of coolant seepage. Here's a picture of the worst gasket...



At the same time, I discovered a prior workmanship issue with a dealer that serviced my transmission while under warranty. It seems they missed tightening one of the bolts holding it to the engine...

 

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Discussion Starter #18 (Edited)
I filled the car with coolant (it took between 8.5 and 9 litres) and have run it for several days now. There's no sign of any further leaks which makes me very happy! I am extremely pleased with how this has turned out.

For anyone about to embark on this project, here are a few things I did and learned that will make the job a little easier. As mentioned before I found nothing technically difficult, just time consuming.

1. Allocate lots of time and don't rush. Creating a clean workspace will allow you a place to store and organize all the parts you take off during the procedure. IMO, this is quite important. No lost parts, no 'extra' parts left over is the goal.

2. Make sure you have the right tools. I've listed some below that are very helpful.

3. Don't reuse gaskets or seals. Some may seem okay to put back in but trying to save a few bucks just isn't worth it given how much time it takes to do this job. You may have to do some parts again if you end up with a leak (ie: water pump cover seal).

4. Although not absolutely necessary, I recommend taking off the EGR valve (replace the gasket with a new one) and EGR purge solenoid. Why? Because they tend to catch up on the wiring harness during removal and re-installation. It's barely 3 or 4 minutes to do and buys you clearance.

5. Remove the water pump cover. Again, not absolutely necessary but creates improved clearance.

6. It's not necessary to remove the water pump (unless it's leaking). A special tool is highly recommended for removal and installation so avoid the expense if you can. New GM water pumps come with the gasket. I'm not sure about aftermarket.

7. Replace the heater coolant inlet fitting (pictured below). It comes with a new retaining clip, 'O' ring and thread sealer (if you buy the GM part). You will need thread sealer if you buy the NAPA equivalent.

8. Disconnect the wiring harness to the ECT sensor. There is also a ground wire that bolts to the engine coming from the same piece of loom. These are located on the rear, lower right side of the engine. This will give you the ability to "gently" pull the engine harness out of the way to access all the crossover bolts. This step 'may' vary by model year.

9. Some bolts cannot be removed (due to clearances), only loosened and pulled back out of the block. When reassembling, remember that ALL bolts should be inserted into the crossover and the gaskets hung over the bolt ends.

10. HAVE AN ASSISTANT HOLD THE HARNESS OUT OF THE WAY DURING RE-INSTALLATION. This will allow you to concentrate on placement, getting each bolt started with your fingers and making sure none of the gaskets slip off the bolts.

11. Don't use any type of sealant/silicone on the new gasket surfaces. They are intended to be installed dry.

12. A small amount of thread sealer on the bolt threads is okay, but none of them pass through a coolant channel so don't go crazy. This is more to ensure the bolts don't loosen off.

13. There is a torque sequence for the crossover bolts. Follow it!

14. Torque the bolts to spec. 18 lb-ft. is the right number. You will not be able to torque the two bolts at the bottom right position because the transmission is in the way so you'll have to approximate.

15. The FSM states that if the EGR valve inlet pipe is removed from the crossover it must be replaced. This is because it incorporates a crush seal connection at the crossover. I did not do this (I suspect most don't) but I wanted to mention it. The risk is an exhaust leak at the connection point.

On with the pictures...

My old seals. It may be hard to see but there are several locations on each seal that show signs of failure.




This is the old heater coolant inlet tube fitting. The risk of a leak from the aged 'O' ring isn't worth passing this by. Definitely an item to replace.



Here is the torque sequence for the crossover bolts. Bolt #6 seems to be the one most people complain about. Using a 13mm swivel socket (not a universal on a regular socket) and an extension will buy you the clearance needed. If you disconnect the ECT sensor and ground mentioned in point #8 above, you will be able to move the harness out of the way for very good access.



Here's a 13mm swivel socket. You'll also find a set of these wrenches quite helpful.



Here are some of the other tools that prove helpful. On the very left is a 3/8" fuel line disconnect tool. This one is metal and more robust for the application. Next is a Lisle 37000 disconnect set. These were great for the heater coolant inlet tube. The hose clamp pliers were great. In the second picture you can see a different type for accessing really tight spaces. These helped in a couple of spots.




Hopefully this helps a little for anyone needing to do this.
 
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