Hi, i have an Impala Ls 2000 V6 3.8 with 80k miles.

a little background first:

i bought this car used like 2 years ago, it was fine until some months ago.

i changed the upper intake manifold cause it has a coolant leak and it hydrolocked, bought one used and ordered a new one, a dorman one.

some weeks ago i was going at 75 mph at the highway and the car made a weird sound like there was something stuck, then the rpm iddle started to go down slowly until the car shutted down, i try to start it back on when it was parked it would cranck and start but dies right away, towed it to my house.

2 days later i called a tow to move it to a mechanic, to my surprise it started right away, still used the tow, the mechanic told me to change the fuel pump battery which we did, also told me that the used part "intake manifold" was leaking too so i ordered a new one, and looks like the old owner removed the thermostat "ordered one of those too".

it was all fine until i used again the highway and hitted 75 mph the car did the same sound and the rpm started to go down, but this time it started 10 mins later after putting the key in on 5 times and then starting it.

my mechanic checked the car to see if there was any error code and there wasnt, the fuel filter is new and ok too.

so i dont know what could be causing this problem?, i think that maybe the coolant is leaking again and hydrolock the car at high speed? i really dont know, im going to change the intake manifold and all that but dont know if that will solve the problem.

what can i do?

the lower intake manifold gaskets are normally also bad on 3800'*. they need to be changed to the felpro aluminum framed gaskets. also dont listen to "mechanics" who tell you to shotgun parts without troubleshooting

https://www.gmforum.com/mechanical-1...ts-l36-297702/
https://www.gmforum.com/mechanical-1...2005-a-304071/

thanks man, how did you exactly did you block the plastic intake?.

so my problem of stalling at highspeed is the bad upper intake manifold?.

also will buy the feelpro.

well if you bought a used one, it is likely as bad or worse than yours for starters. your engine is getting coolant in it by the sounds of it, normally it is either the upper manifold, lower gaskets or a combination of both. and since you can get the dorman kit for the upper i listed and the felpro lower gasket set for less than a hundred bucks all together from rockauto its a good idea to do it all at once. as far as plugging the manifold you have to pull the lower and install the plugs in it.

if you got coolant in the cylinder the plugs could be fouled. i would pull them and look for whitish junk.

Ok thanks, I ordered the piece I will install it the first weeks of January.

I'm going to do it all at once better to be sure than sorry.

which piece? you check the plugs to make sure that was your issue?

The upper intake manifold that has the coolant leak, I ordered the dorman one the same you posted(I had it ordered even before this thread the leak was too obvious lot of coolant arround the piece.

I will check the plug and the lower manifold when I do the upper intake, and check the plugs an all that.

I will have to do it anyway if there'* coolant in the lower intake it must be cleaned and the plugs will be probably full of coolant I hope they aren't but need to check them.

I hope that will solve the stall at more than 75mph, is that common to happen when you have a coolant leak in the manifold?

Hi, I had a similar problem with my chevy Lumina, It would die when it went into passing gear. It ended up a bad injector. once the injector was replaced, problem solved.

Sounds logic will check that too, wouldn't that appear as a check engine light or in the computer ?

bad injector is not a real common thing and on a 3800 it wouldnt die. im thinking the plugs are full of coolant which would make it easier to stall when the coolant gets into the cylinder. not many things cause a 3800 to die, crank sensor, maf, tps, and icm. icm is the most common but will normally be a start cold and die hot thing.

when you take the lower intake off you will need gaskets. and the coolant elbow will brake apart and you will need another. the aluminum ones are the better ones to get, the plastic ones will get brittle and break or at least leak