Thread: motor replacement in a 98 pontiac grand prix

Have had this grand prix for a while but the motor locked up on me the other day. not exactly sure why but will find out once its out and I tear it apart. In the meantime I need to get another motor for it. Found a 98 buick lesabre that was rear ended. heard motor run, sounds good. Is there any differences in these? Both are 3800 series 2 v6 engines. Both are showing rpo code l36. The only difference im seeing is that the lesabre and the grand prix use a different motor mount system but im thinking i should just be able to re-use the grand prix mounts on the lesabre engine so not worried about that.I dont see any reason this motor wont work in my grand prix but thought id post on here just in case. is anybody else familiar with these 2 cars or seeing any potential problems i may have?

Swap all brackets from your GP to the LeSabre engine. Engines are identical.

okay yeah was already planning on doing most of that since have new water pump , ac compressor and alternator on my grand prix engine anyways

Before you fire that replacement up you may want to go ahead and replace the LIM gaskets as they are a known failure point.

I'd be willing to bet that either the UIM failed internally and filled your cylinders w/ coolant causing the lockup, or the LIM gaskets leaked and you spun a few bearings.

Like they said - before you declare the engine dead, pull the spark plugs and spin the motor. There's a good bet that coolant will come out.

It's quite common for these engines to be declared "seized" when they are actually just hydrolocked due to coolant in the cylinder.

I never came back to check this thread within the last few days so unfortunately never saw any of this. I didnt want to tackle the front wheel drive engine so I had my mechanic do it. He did mention cylinders were full of water so im assuming this may have been the problem but the other motor is already in. lower intake manifold gasket was bad, looked like it was ripped through on the one side so that may have been the problem. It was to cold to work outside today but when I get a chance, i do want to rip the heads off and check out the head gaskets just out of curiosity.

I have the other engine in now but now have another concern. I drove the car 2x for about maybe 30 miles combined. today it flashed the oil dummy light so i pulled over and let it sit for about 20 minutes. Then I checked the oil to see if it looked clean and it looked like brand new oil as it should, considering it has maybe 50 miles in this engine.when i went to start it up im hearing top end ticking for about 10 seconds then goes away. I could then continue to hear tapping sound the entire ride home (only about 7 or 8 mile trip) but the tap would come and go away, was not very consistent. the last 2 miles the oil light would stay on or flash on /off every few seconds. The car cant be running that low on oil pressure or it would have had to have started knocking. im driving 50mph so i cant have 0 or very close to 0 oil pressure.

I know this motor sat for about 2 years but i started it and let it run prior to pulling it to install in the grand prix and everything looked (oil temp, oil pressure) and sounded good. im wondering if maybe some old oil is still stuck in the top end not allowing a good signal for the oil pressure sending unit or if maybe the valves are sticking? A friend suggested running about a quart of kerosene in with the oil and letting it run for about 20 mins to clean it out some then changing the oil. Anybody else got any ideas?

The old motor doesn't need the heads off. The gaskets are fine. And if you do decide to do that you will need new head bolts to put them back on properly as they are torque to yield bolts (aka- one time use). You need LIM gaskets and a replacement upper intake manifold and you will likely have a good spare engine assuming the nothing bent when it hydrolocked.

Is the oil full in the new motor? You didn't mention that. How did you check the oil temp and pressure before you pulled it? These cars don't have a true pressure gauge from factory and no oil temp gauge either. The oil pressure sending unit is located on the side of the oil filter adapter. Check to be sure it's dry and the wiring to it is good. Could be a false reading. If in doubt find a good electric gauge and hook it up in it's place and see what the true pressure is.

From sitting that long I could see the lifters bleeding dry and needing to be pumped back up with oil, which would cause the lifter tick you are hearing. Since the tapping comes and goes, does it seem to show up when the oil light comes on?

im just going to scrap the old engine so just wanted to pull the heads off to look at the gaskets. I know they are TTY but not planning on putting them back on. I know the motor has the posibility of being good but im not going to take a chance and keep it as a spare. I wouldnt feel comfortable selling it to anyone and not worth the hassle trying to install in another car not being sure it is good even if i replace the uim and lim gaskets.

I didnt check oil temp that was a typo meant to say coolant temp (just to make sure engine wasnt overheating), and didnt check actual oil pressure just watched the gauge cluster several times to make sure it wasnt showing the oil pressure light coming on for low pressure.I want to check the oil presssure to see the actual reading but no way its reading under 5 and the motor isnt knocking. ill check the seals and make sure the wiring looks good.

when i first start the engine the light is coming on and yes im hearing ticking but cant tell if when im going down the road and the light is coming on if its still ticking. its to faint to hear clearly when your moving. What can i do to get these lifters oiled up good?

and yes oil is dead on at the full mark on the stick, not above or below it at all.

okay so been kind of busy but heres where im at. Have started the motor a few times and ticking seems to be stayng very consistent. Manual gauge is reading only about 6 psi which is pretty low and it is dropping oil pressure as gas pedal is pushed down. oil still looks clean but im not hearing a bottom end knock just ticking on the top end since im guessing its starving for oil. At this point the only thing i can think of is the screen is dirty on the pickup tube or the oil pump is failing? Wouldnt the pressure droping as rpms increase be more likely to be a dirty screen though since the oil pump would be forced to spin faster and at least try to create more pressure? Im not 100% opposed to putting a oil pump in it if need be but to do all that work and still not create enough psi is going to really suck plus cost me some $$$.