2002 Buick 3800

L.Fite · 02-08-2025, 02:23 PM

I got this LeSabre with a 3800...
Is has a upper intake coolant leak...
I can not see where it is coming from...
Is there any water in the upper intake plenum?
It's plastic with aluminum intake lower half.
I've cleaned and dried the top of the motor and it looks like its running around where the plenum and intake come together...
Puddles up on top of the intake and runs down the head onto the exhaust...
Tried snugging the bolts around the plenum don't seem loose, but there are a couple I can't get to with the tools at hand.
The motor is in the car and not taken apart...
Trying to avoid that.
Only has 46000 on it...
Was moms car and I'm keeping it because it gets 30+ mpg going down the highway...and averages 22...
Much cheaper than the dually for tooling around town...

Any 3800 mechanics out here?

Alan Roehrich · 02-08-2025, 03:08 PM

Quote:

Originally Posted by L.Fite

I got this LeSabre with a 3800...
Is has a upper intake coolant leak...
I can not see where it is coming from...
Is there any water in the upper intake plenum?
It's plastic with aluminum intake lower half.
I've cleaned and dried the top of the motor and it looks like its running around where the plenum and intake come together...
Puddles up on top of the intake and runs down the head onto the exhaust...
Tried snugging the bolts around the plenum don't seem loose, but there are a couple I can't get to with the tools at hand.
The motor is in the car and not taken apart...
Trying to avoid that.
Only has 46000 on it...
Was moms car and I'm keeping it because it gets 30+ mpg going down the highway...and averages 22...
Much cheaper than the dually for tooling around town...

Any 3800 mechanics out here?

Yes, they leak between the upper and lower intake, not a hard fix. Flush the orange garbage out and put good green antifreeze in it when you're done.

L.Fite · 02-08-2025, 04:08 PM

Thank for the info.

What I was afraid of...
Wasn't sure there were any water passages.
Should be just gaskets and time?

Alan Roehrich · 02-08-2025, 04:42 PM

Quote:

Originally Posted by L.Fite

Thank for the info.

What I was afraid of...
Wasn't sure there were any water passages.
Should be just gaskets and time?

Yep. Took me a couple of hours on my Firebird. You'll have to bleed the cooling system.

TOSTO RACING · 02-08-2025, 05:32 PM

Do what Alan said and make sure you check those 2 coolant elbows the GM ones are plastic and leak all the time!

24503423 elbow
12565082 elbow
gm numbers

Dorman makes metal ones also for replacement.

Also waterpumps are bad on those and it all looks like its leaking from the same area.

BTR69 · 02-08-2025, 07:32 PM

Check the coolant elbows as stated above. That's what happened to my moms car recently. Not a difficult fix, but still a pain in the arse.

L.Fite · 02-09-2025, 02:21 PM

Quote:

Originally Posted by TOSTO RACING

Do what Alan said and make sure you check those 2 coolant elbows the GM ones are plastic and leak all the time!

24503423 elbow
12565082 elbow
gm numbers

Dorman makes metal ones also for replacement.

Also waterpumps are bad on those and it all looks like its leaking from the same area.

The leak looks like it's coming from driver side...
Pump and elbows already replaced a while back...

L.Fite · 02-09-2025, 02:23 PM

Quote:

Originally Posted by BTR69

Check the coolant elbows as stated above. That's what happened to my moms car recently. Not a difficult fix, but still a pain in the arse.

Yeah it is...
Seems like you have to take half the car apart to work on these things!

67 Post GS · 02-09-2025, 05:08 PM

I would go-ahead and replace the plastic upper intake all together. They will warp over time, and then you put a fresh gasket underneath and it will still leak. Dorman makes a replacement.

4speedracer · 02-15-2025, 11:24 PM

The Dorman intake used to come with a different internal EGR tube to get the heat away from the intake. OE configuration would damage the intake, sometimes leak internal and hydraulic the engine. Would suggest doing the lower intake at the same time, the general used plastic lower intake gaskets also replacements can be gotten in metal with rubber inserts.

02-08-2025, 02:23 PM	#1
L.Fite Senior Member Join Date: May 2020 Posts: 508 Likes: 531 Liked 490 Times in 239 Posts	2002 Buick 3800 I got this LeSabre with a 3800... Is has a upper intake coolant leak... I can not see where it is coming from... Is there any water in the upper intake plenum? It's plastic with aluminum intake lower half. I've cleaned and dried the top of the motor and it looks like its running around where the plenum and intake come together... Puddles up on top of the intake and runs down the head onto the exhaust... Tried snugging the bolts around the plenum don't seem loose, but there are a couple I can't get to with the tools at hand. The motor is in the car and not taken apart... Trying to avoid that. Only has 46000 on it... Was moms car and I'm keeping it because it gets 30+ mpg going down the highway...and averages 22... Much cheaper than the dually for tooling around town... Any 3800 mechanics out here?

02-08-2025, 04:08 PM	#3
L.Fite Senior Member Join Date: May 2020 Posts: 508 Likes: 531 Liked 490 Times in 239 Posts	Re: 2002 Buick 3800 Thank for the info. What I was afraid of... Wasn't sure there were any water passages. Should be just gaskets and time?

02-08-2025, 05:32 PM	#5
TOSTO RACING Senior Member Join Date: May 2007 Location: DRAGSTRIP Posts: 879 Likes: 851 Liked 611 Times in 177 Posts	Re: 2002 Buick 3800 Do what Alan said and make sure you check those 2 coolant elbows the GM ones are plastic and leak all the time! 24503423 elbow 12565082 elbow gm numbers Dorman makes metal ones also for replacement. Also waterpumps are bad on those and it all looks like its leaking from the same area. __________________ 5664 GHI/SA CAMARO Last edited by TOSTO RACING; 02-08-2025 at 05:35 PM.

02-08-2025, 07:32 PM	#6
BTR69 Member Join Date: May 2014 Location: Wilmington NC Posts: 111 Likes: 151 Liked 74 Times in 24 Posts	Re: 2002 Buick 3800 Check the coolant elbows as stated above. That's what happened to my moms car recently. Not a difficult fix, but still a pain in the arse. __________________ William Kilduff 1970 Barracuda (still under construction, indefinitely) 1968 Camaro SS/C

02-09-2025, 05:08 PM	#9
67 Post GS Junior Member Join Date: Aug 2011 Location: Buffalo New York Posts: 79 Likes: 9 Liked 48 Times in 10 Posts	Re: 2002 Buick 3800 I would go-ahead and replace the plastic upper intake all together. They will warp over time, and then you put a fresh gasket underneath and it will still leak. Dorman makes a replacement.

02-15-2025, 11:24 PM	#10
4speedracer Junior Member Join Date: Sep 2011 Posts: 51 Likes: 0 Liked 10 Times in 6 Posts	Re: 2002 Buick 3800 The Dorman intake used to come with a different internal EGR tube to get the heat away from the intake. OE configuration would damage the intake, sometimes leak internal and hydraulic the engine. Would suggest doing the lower intake at the same time, the general used plastic lower intake gaskets also replacements can be gotten in metal with rubber inserts.