3800 cooling system from HELL

[Matthew Jeschke]

I'm to the point where I am ready to put in some sort of stop leak in my cooling system. A friend recommended silver solder but I don't thing they make that anymore?

Anybody have a good stop leak they recommend for a cooling system.

Backstory: I got this 2006 Buick Lucerne nearly 10 years ago with 90k miles on it. It's been a great vehicle aside from junk accumulators on the 4T65E transmission and cooling issues. The cooling system has always leaked as well as the transmission clunking (my theory is the accumulators are cracked). I digress about transmission back to the cooling system. I've since put:

New metal bypass tubes (why bypass tubes??? why??)
New radiator (nearly impossible to swap)
New water pump

Using contrast dye I've checked:

Intake manifold GOOD
No leaks on front of motor (bank1?)
Cannot see easily back of motor (bank2?) but appears find so far as I can see.

However, always a puddle forms under bank 2 at rear of block (near driver side tire).

I can see some spray near the harmonic balancer on the sub fame but nothing on the pullies??

I can see a bit of contrast on under the ignition coil however, there's no puddle there under the vehicle.

I don't think the heads are leaking or the intake. It's not the water pump, or bypass tubes. The heater core and supply lines are not leaking either. The radiator and hoses are good.

My mind is blown. I cannot figure out where this leak is coming from.

Vehicle is great aside from the bleeping tranny clunk due to cheap plastic accumulators and this cooling system I'm constantly chasing leaks in. Long story short, unless somebody knows this system well and were I might fix it... I'm going to dump stop leak in it and hope for the best. Super annoyed great motor otherwise, great power, but perpetually leaky cooling system. It's like GM took this car 99% of the way to great and said well lets just create a leaky cooling system and clunky transmission so we can save 15 cents building it.

 

[bigdog9191999]

If you don't get any other responses I am quite familiar with 3800 stuff.

However I do want to clarify bypass tubes. Is this in reference to coolant elbows?

 

[89Suburban]

This is always my go to. I keep a couple in the tool chest for emergencies.

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@OR VietVet @Tonyrodz are you familiar with this engine and this issue?

 

[Tonyrodz]

This is always my go to. I keep a couple in the tool chest for emergencies.

Best Stop Leak for Cars, Trucks, & SUVs

Put an end to car fluid loss with powerful stop leak additives from AutoZone. Buy online and get free next day delivery or pick it up today at an AutoZone near you.

www.autozone.com

@OR VietVet @Tonyrodz are you familiar with this engine and this issue?

Sorry not familiar with the newer 3800s, only the older late 80's to mid 90s. I'm sure they're not the same.

 

[bigdog9191999]

Same basic setup from 97+. L36 And should be basically identical from 04+ when they switched to the L26 till end of life.


When I get a min I can list out all the places cooling system makes a seal at. This may help visualize where the leak could be. That is if it isn't something like the lower intake gasket. Which can be quite common on a 3800.

 

[bill1013]

Barr’s Pelletized Stop Leak always worked for me. You might consider looking into using it.

 

[Tonyrodz]

Barr’s Pelletized Stop Leak always worked for me. You might consider looking into using it.

Great stuff. Plugged a big hole in the radiator in my 89 Formula.

 

[Matthew Jeschke]

Thanks for the tips! I knew I'd come to the right place. Everybody on here always seems to know their stuff!!! Really appreciate it.

If you don't get any other responses I am quite familiar with 3800 stuff.

However I do want to clarify bypass tubes. Is this in reference to coolant elbows?

Correct I replaced the coolant elbows, twice *sigh*. First time with OEM plastic ones, second time I learned of aftermarket metal ones. The later have held nicely. I also learned that GM spec coolant dissolves the o-rings on those. So I'm using Preston (not GM spec / universal coolant).

This is always my go to. I keep a couple in the tool chest for emergencies.

Best Stop Leak for Cars, Trucks, & SUVs

Put an end to car fluid loss with powerful stop leak additives from AutoZone. Buy online and get free next day delivery or pick it up today at an AutoZone near you.

www.autozone.com

@OR VietVet @Tonyrodz are you familiar with this engine and this issue?

Great to know I'll snag this.

Barr’s Pelletized Stop Leak always worked for me. You might consider looking into using it.

Maybe I'll try this first?

Sorry not familiar with the newer 3800s, only the older late 80's to mid 90s. I'm sure they're not the same.

No clue. It's a GREAT motor otherwise. Efficient and good power. I've had several 3100's and this 3800. My friends also had coolant problems with their 3800's of this vintage. I drove the newer 3500? it's TERRIBLE no power. I'd love to sort this out but making me increasingly frustrated lol

The 4T65E is a great transmission too. However, they obviously went through and cheapened it, in addition to introducing weak points so it eventually prematurely fails much like 4L60E.

Same basic setup from 97+. L36 And should be basically identical from 04+ when they switched to the L26 till end of life.


When I get a min I can list out all the places cooling system makes a seal at. This may help visualize where the leak could be. That is if it isn't something like the lower intake gasket. Which can be quite common on a 3800.

That would be AWESOME if you have an easy way to do that. It maybe I missed a seal I didn't realize. I'd MUCH prefer to fix root issue as apposed to stop leak it.

 

[bigdog9191999]

I will start at the coolant inlet on the driver's side in the intake where the thermostat is. And just follow the cooling system around and mention all the places I know there is a gasket or such ( there are more than one thinks. )

The gasket around the stat itself seals the stat and housing.

Lim these should be metal by this year but does not mean they could not fail. The rubber around the coolant ports can still degrade.

Upper intake to tb gasket

Gasket between upper and lower intake. Should be thinking plastic with rubber around the sealing surfaces. ( There are passages from the lim to the tub, thus sealing points in-between everything)



There is a port with a "cap" under the Tb in the lower intake that has a gasket ( very rarely any issue here)

From there it all flows through the heads/block through passages to the passenger side on this side you have.

Front cover to block ( OEM is a coated metal gasket. )

Pump on the front cover.

Elbows. One from lim and one from front cover to/through alt bracket.


Front cover / hose to radiator. Rad to engine and rad to overflow.

 

[B-train]

I chased a mystery leak on my daughter's 2008 Lucerne 3.8L. Did a Google search after racking my brain and found 1 thread that mentions a coolant cover on the back of the motor........blocked by the bell housing of the transmission. The article read similar to your post and that is what they eventually found to be the problem. I'd look for some pictures of the Series III 3.8L and see if you can correlate it.

I put in some K-Stop stop leak and its been fine ever since. That stuff works magic. I won't pull a trans to fix a coolant leak on a $1500 car.

@Matthew Jeschke

 

[Matthew Jeschke]

@bigdog9191999 thanks! I'll run through that list.

@B-train LOOKS EXACTLY like where the big puddle is under. I wouldn't be surprised if that is it!

 

[TollKeeper]

@OR VietVet - Hopefully you can help my memory here...

If memory serves correctly, the water pump bolts to the timing cover, and there 2 water pump gaskets, one on each leg, or a single large one, depending on year.

Then a timing cover, and gasket, that the coolant also passes thru, that mounts to the front of the engine block.

On my last 3800, the timing cover gasket is what had failed. It took me forever to figure out too, as I wasnt there to fix a coolant leak, but a power steering leak, that I had to dismantle all that to get too. Only found the issue after reassembly.

It can fail and leak internally, or externally. So if you are not getting a chocolate milk oil, consider yourself lucky! When it fails externally, it can be hard to trace, as the belts, pulleys, accessories, and harmonic balancer throw the coolant everywhere.

When mine failed, it would not leak when cold, but only when the engine was up to temp. Metals expanding/contracting. I mention this because if you try to find the leak by putting pressure in it, it might not leak.. But it also might.

 

[OR VietVet]

@TollKeeper, sounds like your memory is spot on.

I wonder one thing though. Has the cooling system been pressurized with a coolant pressure tester? If has and was said it has, I missed it.

 

[Matthew Jeschke]

@OR VietVet - Hopefully you can help my memory here...

If memory serves correctly, the water pump bolts to the timing cover, and there 2 water pump gaskets, one on each leg, or a single large one, depending on year.

Then a timing cover, and gasket, that the coolant also passes thru, that mounts to the front of the engine block.

On my last 3800, the timing cover gasket is what had failed. It took me forever to figure out too, as I wasnt there to fix a coolant leak, but a power steering leak, that I had to dismantle all that to get too. Only found the issue after reassembly.

It can fail and leak internally, or externally. So if you are not getting a chocolate milk oil, consider yourself lucky! When it fails externally, it can be hard to trace, as the belts, pulleys, accessories, and harmonic balancer throw the coolant everywhere.

When mine failed, it would not leak when cold, but only when the engine was up to temp. Metals expanding/contracting. I mention this because if you try to find the leak by putting pressure in it, it might not leak.. But it also might.

Strong possibility this is source of splatter along subframe in that area. I can see a small amount of coolant towards bottom of engine if I look closely in that area. The water pump was easy enough but not like anything I'd seen before. It was dirt cheap as it's not much of anything but a cover and turbine / blades. I keep however, wondering if I did the gasket wrong as there is some coolant in that area but not a drop around pump. Thanks for the tip!

@TollKeeper, sounds like your memory is spot on.

I wonder one thing though. Has the cooling system been pressurized with a coolant pressure tester? If has and was said it has, I missed it.

I hadn't mentioned that. It has, and it holds pressure long enough to lead one to believe there maybe no issue. However, there's always a pool of coolant under the rear driver side corner of the oil pan... Near where it was mentioned there's a coolant seal in the bell housing. I suspect that seal is shot.

 

[OR VietVet]

 

[OR VietVet]

More Information for FEL-PRO BS40708

At RA, it is listed as a crankshaft seal and at the bottom of all the choices, it shows 2 choices for the REAR seal kit.

 

[Matthew Jeschke]

Thanks for sharing that... but OMFG. No way can that be done without pulling the engine???

Have to take the balancer off for which I'm not sure if there's enough space in the engine bay to do that?? Maybe I could drop the subframe down a bit to get access?

Long story short, thanks for sharing that 100% on my way to get leak stop now. Probably not even worth fixing / trash the car before I go that far. Sad they made such a leaky motor as is good otherwise.

 

[OR VietVet]

If you can get an engine cradle to support the engine from above and then remove the transmission, the access is there. Is a transmission removal doable without removing engine? Check out some videos to see if it is even doable. BUT, it may not be worth it for that car.

 

[Matthew Jeschke]

I want to report back. I added the Bars cooling system tablets. So far not a DROP of coolant under the vehicle. On another note, they also made my engine run smoother! It doesn't vibrate nearly as much anymore. Oddly I have a newish water pump (installed 10k miles ago?). But I thought there was an issue with the balancing shafts (maybe slightly out of time / phase). However, seems it was the water pump causing engine to vibrate like that! I'd have never thought.

Additionally I took a long hard look at the timing cover. It actually looks doable in the engine bay with the right puller (small enough to fit). There's some space between the upper unit body member and the subframe to possibly pull the harmonic balancer. That be the cause it's just a job of removing all the components in front of it. I'd imagine it'd take me about 8 hours assuming I could fit a tool on to remove the balancer. I'll tell you this engine isn't as well thought out as the small block. It's kind of piecemealed together and difficult to access for larger maintenance projects. Maybe that's just par for the course on front wheel drive vehicles?

Long story short thanks for the help! So far so good!

 

[OR VietVet]

I want to report back. I added the Bars cooling system tablets. So far not a DROP of coolant under the vehicle. On another note, they also made my engine run smoother! It doesn't vibrate nearly as much anymore. Oddly I have a newish water pump (installed 10k miles ago?). But I thought there was an issue with the balancing shafts (maybe slightly out of time / phase). However, seems it was the water pump causing engine to vibrate like that! I'd have never thought.

Additionally I took a long hard look at the timing cover. It actually looks doable in the engine bay with the right puller (small enough to fit). There's some space between the upper unit body member and the subframe to possibly pull the harmonic balancer. That be the cause it's just a job of removing all the components in front of it. I'd imagine it'd take me about 8 hours assuming I could fit a tool on to remove the balancer. I'll tell you this engine isn't as well thought out as the small block. It's kind of piecemealed together and difficult to access for larger maintenance projects. Maybe that's just par for the course on front wheel drive vehicles?

Long story short thanks for the help! So far so good!

Welcome to the world of transverse engines.