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.

Alumaseal Radiator Stop Leak 0.75oz

Shop for Alumaseal Radiator Stop Leak 0.75oz with confidence at AutoZone.com. Parts are just part of what we do. Get yours online today and pick up in store.

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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.

Alumaseal Radiator Stop Leak 0.75oz

Shop for Alumaseal Radiator Stop Leak 0.75oz with confidence at AutoZone.com. Parts are just part of what we do. Get yours online today and pick up in store.

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.

Alumaseal Radiator Stop Leak 0.75oz

Shop for Alumaseal Radiator Stop Leak 0.75oz with confidence at AutoZone.com. Parts are just part of what we do. Get yours online today and pick up in store.

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.