Odd Overheating Issue

[300sflyer]

Same here. I never had the issue.

Technically by '04, most N*'s had this issue worked out. It was early gen N*'s that this was a prevalent issue on.

The production date on mine is June of 2004. It certainly was not fixed on mine. All is good now though.

[05GXPTriCoat]

Well I got it dropped, drilled-tapped-studded, heads, intake, water crossover back on. One more timing chain and it's on the way to running by this Saturday afternoon. None of the head bolts stripped, but 3 of them on the front/left bank did not "break" when removing them. My guess is they were not torqued enough to stretch them correctly and you could see on 3 and 5 where the coolant had slightly de-carboned the pistons. No water in the oil (whew) though and the heads and block both checked exactly true. No cracks or other issues except that there were some bolts in other places that had no torque when removing them. I have really only put about 15 or so good hours into this whole job, so overall I'm pleased with how it's going especially not having done it before. Lots of disconnecting and double checking have prevented any catastrophes. I can't imagine trying to do this with jackstands and an engine hoist...the lift has been a blessing for sure.

[300sflyer]

Sounds like you are having fun. I had no access to a hoist, so I paid a local garage to do mine. You will be pleased with the results when it is all done.

[Juggernaught]

Thanks for the update, good to hear that it's going well. You have my deep respect and sympathy. By your description, it sounds like this might have been due to an assembly error with not enough torque applied to the head bolts? If so, that might explain the early failure. Maybe the engine was assembled on a Monday or Friday?

[05GXPTriCoat]

You know I was thinking the same thing Juggernaught...haha!

300sflyer, I called so many garages I can't even count them. Only 2 said they would do it, one said $2000+ and a month of wait time the other said up to $4000 and no guarantees...uh sure, sign me up... Oh well, at least I know things are being done right and once this is done it will be better than before.

[05GXPTriCoat]

So I now have a beautiful GXP sitting in my driveway again! So glad that I finished this little project up... Everything went super-smooth thanks to some help from family and a heated garage with a lift and compressor! Had a little scare driving home when the temp gauge started to creep up. Looks like (as best I can figure) the thermostat is doing exactly what it is supposed to. It goes up maybe two widths of the needle when pulling a longer hill then comes right back and hovers a touch over the 200 mark where it sits rock steady most of the time. I still feel like there is some air trapped in the system as the heater is not a hot as I "think" it should be. It runs fantastic though even on a tank of old gas, I really missed that sound, the slight tug of the wheel when the tires are scratching for traction and the speedometer moving towards illegal speeds faster than I remember....lol! I will work on getting the parts list together (maybe make it a sticky?)that I used and post some pics of the things that are really important. I probably won't do a step by step as everyone has a different approach to things.

[300sflyer]

Glad it all went well for you! Mine did the same thing at first too. The temp gauge would rise a bit, and then drop back down repeatedly. In my case, it was air still trapped in the system. I ended up taking the upper rad hose off the rad, and pouring more antifreeze into the hose itself. This did the trick.

[skregal]

I hope I never have to do that repair.

Your "the man" for taking it on yourself.

[05GXPTriCoat]

Thanks skregal! I hope you don't either... Honestly though, it wasn't that bad. If you look at the big picture yes it was overwhelming, but taking it a step at a time things went alright. Happy to report that after 2 days of driving 50+ miles round trip for work it's running fine, temp needle has settled down to no creep and the heater is blowing hot like it should.

[98SSE]

Congrats , this problem/repair is the reason I haven't gotten a GXP.

[05GXPTriCoat]

**Update**

Well, 10,000 miles later and zero issues with overheating. I have run it on long trips through the mountains and haven't been afraid of using the loud pedal getting on the highway. Mileage has settled to around the 20.2-20.4mpg in mixed 2-lane/highway driving. Which may not sound great,but with the hills where we live don't provide much assistance in improving that number.

[PhoenixStar]

Good to hear!

I got nervous today with my 05 GXP. This is my first summer with it and it always did fine until it did something I hadn't experienced before. Normally the temp holds at 200 or within 1 tick either way like yours did.

Today it was 94 degrees and I was climbing up a steep 2 mile long hill at around 75 mph with the ac on. I was on the throttle under moderate acceleration going up this hill when I noticed the AC go a bit humid for a few seconds and within a few mins later the temp gauge may have been about 5-7 ticks further off the 200 mark towards the hot end. Then cruising same speeds on level ground it was ok, but when I gave a little punch on the throttle to pass it went up again 5-7 ticks over, then would cool down to the 200 mark again within 20 sec of letting off the throttle.. I never seen it do this before, hopefully it was because it was so hot outside, and not a early HG sign. Even on days when it was 90 it wouldn't do this before.

[RonaldCeri]

It seems that the button to go to the first unread post in a thread is gone. Is that going to be brought back? It was really helpful for the bigger threads like MIKAs.В 

[CMNTMXR57]

Good to hear!

I got nervous today with my 05 GXP. This is my first summer with it and it always did fine until it did something I hadn't experienced before. Normally the temp holds at 200 or within 1 tick either way like yours did.

Today it was 94 degrees and I was climbing up a steep 2 mile long hill at around 75 mph with the ac on. I was on the throttle under moderate acceleration going up this hill when I noticed the AC go a bit humid for a few seconds and within a few mins later the temp gauge may have been about 5-7 ticks further off the 200 mark towards the hot end. Then cruising same speeds on level ground it was ok, but when I gave a little punch on the throttle to pass it went up again 5-7 ticks over, then would cool down to the 200 mark again within 20 sec of letting off the throttle.. I never seen it do this before, hopefully it was because it was so hot outside, and not a early HG sign. Even on days when it was 90 it wouldn't do this before.

Generally speaking, even on a hotter than normal day, the car *may* run warmer all the time, especially under a heavier load or working harder than normal. However it sounds very sporadic in your instance and the sign of a possible air pocket. Meaning, the system isn't perfectly sealed and pressurized as it should be. Leading me to believe air is somehow getting in. And a prime suspect of that is...

Again, not a 110% diagnosis from my arm chair, but...

[CMNTMXR57]

It seems that the button to go to the first unread post in a thread is gone. Is that going to be brought back? It was really helpful for the bigger threads like MIKAs.В 

Never knew that was a feature here...

Just toggle on the pages.

[PhoenixStar]

Good to hear!

I got nervous today with my 05 GXP. This is my first summer with it and it always did fine until it did something I hadn't experienced before. Normally the temp holds at 200 or within 1 tick either way like yours did.

Today it was 94 degrees and I was climbing up a steep 2 mile long hill at around 75 mph with the ac on. I was on the throttle under moderate acceleration going up this hill when I noticed the AC go a bit humid for a few seconds and within a few mins later the temp gauge may have been about 5-7 ticks further off the 200 mark towards the hot end. Then cruising same speeds on level ground it was ok, but when I gave a little punch on the throttle to pass it went up again 5-7 ticks over, then would cool down to the 200 mark again within 20 sec of letting off the throttle.. I never seen it do this before, hopefully it was because it was so hot outside, and not a early HG sign. Even on days when it was 90 it wouldn't do this before.

Generally speaking, even on a hotter than normal day, the car *may* run warmer all the time, especially under a heavier load or working harder than normal. However it sounds very sporadic in your instance and the sign of a possible air pocket. Meaning, the system isn't perfectly sealed and pressurized as it should be. Leading me to believe air is somehow getting in. And a prime suspect of that is...

Again, not a 110% diagnosis from my arm chair, but...

I'm hoping that the "..." you're referring to isn't the "..." everyone fears. I drove it under normal highway circumstances today in 92 degree weather for 40 mins and it held fine at 200 even with a light to moderate throttle here and there, no fluctuations. I climbed a half a mile long mountain also at about 25 mph, and noticed when I came to the top it was about 2-3 clicks past 200. I waited in idle for about 20 seconds, and then the needle rocketed back to 200 within a second.

I'm starting to think one of 2 things, either the temp gauge is getting wacky, or possibly a sticking thermostat, causing the rapid plummet I witnessed when it opens, and may be why suddenly the temp climbs at random.

If you are suggesting a leak in the system, I'll replace the coolant res cap first, I'm sure it's the original 11 yr old cap. Oil looks clean too, so hopefully for now it's not "..."

[CMNTMXR57]

When the engine is cold, does it seem to get really hot, then suddenly cool, much the same as you're seeing in the heat? Could be a thermostat, although I don't know that this would be an issue on a fully warmed engine.

A properly operating cooling system is sealed and pressurized when in use. This is done to purge air and increase the boiling point of the coolant in the system. If it gets hotter sooner, that means air could be getting in.

Loose hose, block freeze plugs, head gasket, bad resevoir cap, etc, etc... A cooling system pressure test would eliminate tell you and perhaps help you find where any issue is.

[PhoenixStar]

When the engine is cold, does it seem to get really hot, then suddenly cool, much the same as you're seeing in the heat? Could be a thermostat, although I don't know that this would be an issue on a fully warmed engine.

A properly operating cooling system is sealed and pressurized when in use. This is done to purge air and increase the boiling point of the coolant in the system. If it gets hotter sooner, that means air could be getting in.

Loose hose, block freeze plugs, head gasket, bad resevoir cap, etc, etc... A cooling system pressure test would eliminate tell you and perhaps help you find where any issue is.

No nothing when cold to hot. Only seems to climb under moderate+ loads, and it's only been 2 days or so, so I haven't been able to detect any other patterns as to when else this is happening. If I'm cruising on relatively level highway at 75/80mph for 1hr+ it doesn't seems to affect anything, neither does sitting in terribly hot stop and go traffic for 30 mins. I'll probably get it pressure tested like you said, no use getting nervous if I can't get some real data first.

[05GXPTriCoat]

Mine temp needle will climb (post-repair) on the longer, steeper grade hills I've been on. That said, it's only a few widths of the needle and as soon as the load eases the needle drops right back down. It's not anything that makes me nervous and as others have said hills place a load on the engine and trans so heat is the by-product. In addition to the cap, check the water pump belt and tensioner while you're under the hood. At 74,xxx miles, the tensioner pulley bearings had gone bad and the belt had started to shred on mine. Obviously, I'm not diagnosing that as your issue, but it won't hurt to look at everything considering the age of the car, miles, summertime temps, etc.