My park ave is using coolant from the overflow tank between oil,changes.uses about a quart or so of coolant. I change oil every 4000 miles and that'* when I top off the overflow bottle,no external leaks found,replaced upper manifold and gaskets approx 25000 miles ago with OE parts. I have only owned the car for past 25000 miles.no codes or drive ability issues. Ninety percent of driving is highway,65-70 mph, I drive 65 miles a day. Is it normal for the 3800 to use some coolant under these driving conditions? Could it be the lower intake gaskets? Oil level is not rising like it is filling with coolant. The last thing I want to happen is wipe out bearings due to contamination,I haven't heard any issues of head gaskets with the 3800. Thanks for your help

More than likely, either the upper plenum gaskets or the lower intake manifold gaskets. Or, maybe a coolant elbow just in front/lower than the alternator. You would see a leak on the side of the engine.

on the ones i have done the plastic lim gaskets were worse than the uim, and the elbows normally break into a million pieces, so its always a good idea to do aluminum felpro lower gaskets, aluminum elbows, and uim at the same time. to answer your question its likely the lowers blown out and getting burned. they dont use or burn coolant if its working properly

Thank you for the advice,I'm a long time nissan technician and am not real familiar with other products. I bought the park because I changed dealers and am driving much further than before and wanted a comfortable car to drive.I couldn't beat the price for a nice older car, I really like the car and it'* getting around 28mpg Has GM updated the lim gaskets and should I replace the plenum again or just the gaskets on the upper? I read somewhere that the dexcool is garbage,what do you think?

Research shows its not the coolant. Just a **** poor design with plastic gaskets. Upgrade the lower manifold gaskets to metal framed ones and they cures it. As far as the upper, block the coolant ports and your all set.

The PA is a very safe & comfy car!
My 97 PA was also loosing about the same amount of coolant and could not see where it was going. Luckily it was not mixing into oil & coolant overflow reservoir remained clean.
It was leaking from the lower manifold gasket and really could not see it, until I power washed the engine well.
I would not wait to replace the LIM gasket, get er done.
The Fel pro aluminum LIM kit is good quality. Get the both sides of mating surfaces spotless/clean.

Here is the aluminum Dorman elbows kit. Dorman # 47065HP

I would do a pressure test first.....other thing to try is a dye, and black light, if the leak is that small......

Thanks again for all the advice,Mike1995 mentioned blocking coolant ports on the upper,what do you mean? Imposing to do the lower with the fellow kit and dorman elbows,have to wait until after Christmas now,will keep close watch on situation till then

its not a bad job just takes a while because of all the extra stuff you have to take off and put back on
https://www.gmforum.com/mechanical-1...2005-a-304071/

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

Hello again, I replaced the lower and upper gaskets today. Just like you guys said the lower gaskets were blown out at the coolant passage seal on both banks,used all GM oem parts cause I have a friend that works in parts at a Chevy store. Also changed the oil and cleaned out the throttle body. Did the job at work today on my day off,much easier with a lift and all my tools. Took about 3.5 hours to complete,it was much easier than resealiling a Nissan lower intake! Thank you guys for all your help and advice,much appreciated!