Possibly overheating

[NerdPower]

99 Pontiac Grand Prix GT 3800

My car has been acting weird lately. Usually the car starts instantly all the time but lately if its been sitting over night or for a few hours it takes a minute to crank. It acts like it doesn't want to start but once it does you can turn it off then back on and it starts instantly.

When you start driving the car the temp gauge will start to rise like normal but when it gets to about 195 it instantly drops down to 175-180. Then it rises again to about 200 and will stay there for about 15-20 mins of driving. Then when you stop at a light the outside temp on the hvac display will start to rise 20-40 degrees more then what it actually is outside. Then the coolant temp starts to rise to 235-240 and the fans come on. As I drive it will come down to 215-220 until I stop or park again. When I open the hood both radiator hoses are rock hard and really hot. Engine feels hotter then its suppose to be. I already replaced the thermostat(twice), coolant temp sensor and radiator cap.

Any ideas?

[bmx6454]

any white smoke out the tail pipes when you first cold start it?

[99XC600]

Sounds like you have air in the system. Have you checked your coolant levels to see if you're consuming any? Check for any signs of wetness on the manifold bolts and by the coolant elbows?

[FordMan77]

Check your fuel pressure regulator. Pull the vac line off and see if gas comes out. If so, replace the FPR.

On the overheating issue, did you bleed the cooling system properly when you did the t-stats? These engines are very picky on having air trapped in the system and will do what you described when there is. There is a proceedure on here if you search " cooling system bleed" or something like that. It's been talked about a lot.

[NerdPower]

any white smoke out the tail pipes when you first cold start it?

No

Sounds like you have air in the system. Have you checked your coolant levels to see if you're consuming any? Check for any signs of wetness on the manifold bolts and by the coolant elbows?

Yes I've had to add coolant to it. I topped it off yesterday and today it's down a couple of inches from the filler. It is wet right above the water pump and I noticed this black plastic like thing hanging out from between the block and I guess manifold(?). I already had the intake manifold gaskets replaced unless he only did the upper.

Check your fuel pressure regulator. Pull the vac line off and see if gas comes out. If so, replace the FPR.

On the overheating issue, did you bleed the cooling system properly when you did the t-stats? These engines are very picky on having air trapped in the system and will do what you described when there is. There is a proceedure on here if you search " cooling system bleed" or something like that. It's been talked about a lot.

I did it a few times. Where exactly is the fuel pressure regulator?

[bmx6454]

ahhh, coolant above the water pump points towards your coolant elbows. your not seeing coolant puddling on the ground??

[99XC600]

No



Yes I've had to add coolant to it. I topped it off yesterday and today it's down a couple of inches from the filler. It is wet right above the water pump and I noticed this black plastic like thing hanging out from between the block and I guess manifold(?). I already had the intake manifold gaskets replaced unless he only did the upper.

Elbows will need to be replaced. Process is as follows

1. Disconnect negative battery cable
2. Drain Coolant
3. Remove Serpentine Belt
4. Remove Alternator
5. Disconnect Heater Hoses
6. Remove Tensioner assembly
7. Remove Elbows
8. Remove broken pieces of elbows from assembly and intake (Yes, they will break)
9. Insert new elbows and re-assemble (Should take about an hour)

While you are at it, check for any signs of leakage on the driver side of the engine, look for signs of pooling or staining on top of the transmission. If you do, you will need to replace the lower LIM gaskets as well.

[FordMan77]

Facing the motor from the front end, the fuel pressure regulator is on the fuel rail towards the right side. A little round thing about 1" diameter with a single black vacuum line attached to it.

[NerdPower]

Problem solved....I think?!?!? Will see tomorrow. I changed the water pump and poured antifreeze into the block where the thermostat is. I bleed the system and it seems like it worked. I think air was trapped in the block like someone mentioned and the water pump looked original.

[NerdPower]

Facing the motor from the front end, the fuel pressure regulator is on the fuel rail towards the right side. A little round thing about 1" diameter with a single black vacuum line attached to it.

There was no fuel in the vac line so I'm thinking it's time for a tune-up.

[FordMan77]

You don't want to see fuel come from that vac line. If it's dry its good. Wet= bad FPR.

And plugs and wires are a good idea if they're old. Just don't use any platinum plugs. Copper or irridiums only in these motors. Lifetime wires from Autozone and you're set. Gap to .052-.055.