Thread: overheating - loss of power

Originally Posted by Robotech

To answer one of your original questions, I know my Grand Prix GTP (97) has what GM calls a "Limp-Home mode". If the coolant temperature reaches critical levels, the computer will shut off half the cylindars for a while to let the others cool off. After a while the computer will turn the dead cylindars back on and turn off the ones that had been running to cool them off. You don't want to drive more than 50 miles in this condition or bad things happen. Obviously there is a serious reduction in power when in limp-home mode. a

Sounds like you did suffer damage though as you have coolant in the oil. You could have damage to head or LIM gaskets or even cracked heads. Run a compression check if you haven't already and hopefully you'll find the issue there. If not, it may be time to tear down the engine to find the problem.

Next time, when the SES light comes on and you see the temp rising, pull over and let the engine cool off. It's much cheaper that way. Also, a flashing SES light always means that you have a missfire.

Thanks for the info, still havent done a compression test on it yet, a few mobile mechanics say it sounds like a head gasket, and from there expierience with 3800's it probobly is, and the mechanics at local shops say it sounds like lim gasket and the 3800's rarely have head or head gasket problems. so I will narrow it down with the compression tes next weekend. would of been sooner but I have two other vehicles, and low funds, so no hurry, can't wait though, I miss the GP.

Well first of all Merry Chrismas and/or Happy Holidays to all!!!
I finally got a good compression tester, strap to hold engine forward etc. I want to do a compression test, manual says should be done at normal operating temperture, don't want to run vehicle do to water in oil tank, Can't I just do the compression test on a cold engine and get enough reading to tell if my hg is bad or heads are cracked, or should I just change the oil, and run it for 5 - 10 min to get it at operating tempature. The oil stick isn't terribly white, just got some white bubbles in it, its not thick at the top oor anything like that, so wonder if I can run it like that for 5-10 min with out hurting engine any more Please let me know what you think.
Thanks.

Originally Posted by grand prix newb

Thanks for the info, still havent done a compression test on it yet, a few mobile mechanics say it sounds like a head gasket, and from there expierience with 3800's it probobly is, and the mechanics at local shops say it sounds like lim gasket and the 3800's rarely have head or head gasket problems. so I will narrow it down with the compression tes next weekend. would of been sooner but I have two other vehicles, and low funds, so no hurry, can't wait though, I miss the GP.

Originally Posted by grand prix newb

Well first of all Merry Chrismas and/or Happy Holidays to all!!!
I finally got a good compression tester, strap to hold engine forward etc. I want to do a compression test, manual says should be done at normal operating temperture, don't want to run vehicle do to water getting into oil tank, Can't I just do the compression test on a cold engine and get enough reading to tell if my hg is bad or heads are cracked, or should I just change the oil, and run it for 5 - 10 min to get it at operating tempature. The oil stick isn't terribly white, just got some white bubbles in it, its not thick at the top oor anything like that, so wonder if I can run it like that for 5-10 min with out hurting engine any more Please let me know what you think.
Thanks.

Nevermind I better do the right/safe thing and just change the oil & filter first, and then get it to operating temperture to do the compression test.

Originally Posted by Deimos

Wow no one mention the plastic upper plenum that always seems to go bad. The elbows do go bad but they are cake and only like 10 bucks in a help kit. Pull off that beauty shield and see if and thing is leaking and pooling on your lower intake manifold.

Thanks for the advice bud, I already checked under shield, and looks like its leaking between lim and head, not between uim & Lim, So I just want to do a compression test to make sure hg and head is ok, the oil is rusty collored, but I here a leaking lim could do that.
Tempted to do compression test on cold engine to see what those #'s are and if its enough to tell me anything about hg or head.

Sh%t
I ran car for 5 - 10 min to get it to operating temperture,
Did compression test 3x on each cylinder and here are the results
#1: 155 -150 - 150psi
#2: 150 - 150 - 150psi
#3: 80 - 80 - 80psi (sh@t-f%ck)
#4: 160 - 160 - 160psi
#5: 170 - 170 - 170psi
#6: 180 - 175 - 175psi
Looks like hg or head right?

Originally Posted by grand prix newb

Thanks for the advice bud, I already checked under shield, and looks like its leaking between lim and head, not between uim & Lim, So I just want to do a compression test to make sure hg and head is ok, the oil is rusty collored, but I here a leaking lim could do that.
Tempted to do compression test on cold engine to see what those #'s are and if its enough to tell me anything about hg or head.

Yeah. Maybe when you take it apart you might even find a chipped piston.

Originally Posted by grand prix newb

Sh%t
I ran car for 5 - 10 min to get it to operating temperture,
Did compression test 3x on each cylinder and here are the results
#1: 155 -150 - 150psi
#2: 150 - 150 - 150psi
#3: 80 - 80 - 80psi (sh@t-f%ck)
#4: 160 - 160 - 160psi
#5: 170 - 170 - 170psi
#6: 180 - 175 - 175psi
Looks like hg or head right?

Sounds like hg or piston. Cost me $1056 for two new hgs, uim gasket, lim gasket, head studs, em gaskets, vc gaskets, coolant flush, water pump, thermostat, plugs, and wires. Of course, that was paying a shop to do it of course. You could do a coolant system leakdown test to try and cancel out a bad piston and/or verify its just the hg.

Originally Posted by JoelW98GTP

Sounds like hg or piston. Cost me $1056 for two new hgs, uim gasket, lim gasket, head studs, em gaskets, vc gaskets, coolant flush, water pump, thermostat, plugs, and wires. Of course, that was paying a shop to do it of course. You could do a coolant system leakdown test to try and cancel out a bad piston and/or verify its just the hg.

Is there a name for every type of test, or is that different from a cylinder leak down test?And if so what do I need a vacume pump?
Thanks

Well some one said if it were the rings causing that low of compression then there would be blue smoke. I'll try squirting oil in #3 and see if compression goes up any.

Originally Posted by 01GTP

Yeah. Maybe when you take it apart you might even find a chipped piston.

By the way why would you say that, are the grand prix 3800 series 2 engines that cheap on there stock parts.

Oh well regardless of what is wrong, a friend of mine said I should look to geting another engine, (125000 miles on this engine).what you guys think, fix this one (I have the wrenching skills) but would I be rebuilding from bottom/up. Or get another.

A gentlemen from another forum said these engines run into injector/oring probs and that could be leaking compression, any truth to that?
And one other thing is I know I have a leak between the lim and head, could that also cause that 80 psi reading in # 3 cylinder. better do the coolant leakdown test, before I get into that,I guese. Thanks for the help guys.

no and no.

Originally Posted by 01GTP

no and no.

Thanks, looks like it time for a new head or hg then, how well are these engines once a problem like water getting in the oil, is, would I be better off looking for another used engine, or if I replace gasket's, am I looking at replacing the bottom end componants do to water in oil. I havent ran it at all since problem started except for having to move it a block one time and then to get it to operating temperture to do compression test.

There is a good chance you will be fine, run a few qts threw the lifter valley before you put the intake back on.

Originally Posted by 01GTP

There is a good chance you will be fine, run a few qts threw the lifter valley before you put the intake back on.

Well I had major non stop issues with other engines that got water in the oil, Mainly cause I am a poor 50,000 a year suporting 5 family man, so I don't think I am gonna f- with this engine. hows $550.00 for a used 3.8 with 150,000 miles on it sound?

Originally Posted by grand prix newb

Well I had major non stop issues with other engines that got water in the oil, Mainly cause I am a poor 50,000 a year suporting 5 family man, so I don't think I am gonna f- with this engine. hows $550.00 for a used 3.8 with 150,000 miles on it sound?

Well forget about that to many miles, and probobly hasn't had it tc and all the up to date maintenance done for that many miles.

Well did the wet compressiontest on #3 cylinder and it was 10 psi more, so 90 wet 80 dry, is that enough to say there is a prob with ring, The end of the adapter to compresion tester was oily(normal after wet test) but had some foriegn material on it hope it wasn't steel particles. it fell off my finger before I could get to a magnet. going to test again and see if any other particles stick to end of adapter. anyway how about the 10 psi difference? Retested wet no particles, but its time to tare this ***** apart.