1999 Tahoe Overheat - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Already Gone** · 06-12-2017, 03:39 PM

About 2 weks go i took my 1999 Tahoe (5.7 Vortec, 4L60, full Police Package ) and since it just went over the 100,000 mile mark had the orange antifreeze changed to the green and a new thermostat ( Stant ) installed. I've only done about 100 miles since with driving around the City since I had that done. This morning I headed out of town and about 30 miles out my temp gauge starts to really go up. I've seen that before so keep driving but the gauge kept climbing. When it hit 260 and I pulled over and shut her down. Lifted the hood and saw a little water, not antifreeze, dripping on the pas side from near the air cleaner. I dint blow a hose and no antifreeze leaked out. Truck would turn over but not start. Called a tow truck and he took about an hour to get there. Just before he hooked up I checked ans temp gauge was down to cold. I tried starting the truck and it started but ran rough and I didnt hear any obscene noises from the engine. I am clueless as to may have happened here, has anyone got an idea. Oh yea its a California vehicle if that makes any difference cause of the extra emissions thing. Hopefully I didnt lunch the motor.

**Already Gone** · 06-14-2017, 10:37 PM

I thought somone for sure would have a thought on this. Well there is antifreeze in the oil but she still runs, but lumpy. Anyway had her towed home and parked her in the garage awaiting a heart transplant. A thought occured to me today that although the engine only had 101,000 miles it was a Fire Dept vehicle so I bet there are mega idle hours on the engine as well.

MYTQUIK · 06-15-2017, 12:17 AM

Sounds like it could be a head gasket issue.

sntrym95 · 06-15-2017, 07:27 AM

My initial thoughts are that the green anitfreeze that was added was not the universal type and caused a clog in the cooling system if all of the old antifreeze was not flushed out properly.

Other thoughts are that the new tstat stuck closed and caused overheating, there was still air in the system because it wasn't bled completely leading to a bubble near a spot where the gasket edges are close.

I would not go straight for the head gasket. Look at the intake gaskets first. If antifreeze is in the oil, it could just be leaking from the intake gasket into the lifter valley. Quick and easy fix.

06-12-2017, 03:39 PM	#1
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,231	1999 Tahoe Overheat About 2 weks go i took my 1999 Tahoe (5.7 Vortec, 4L60, full Police Package ) and since it just went over the 100,000 mile mark had the orange antifreeze changed to the green and a new thermostat ( Stant ) installed. I've only done about 100 miles since with driving around the City since I had that done. This morning I headed out of town and about 30 miles out my temp gauge starts to really go up. I've seen that before so keep driving but the gauge kept climbing. When it hit 260 and I pulled over and shut her down. Lifted the hood and saw a little water, not antifreeze, dripping on the pas side from near the air cleaner. I dint blow a hose and no antifreeze leaked out. Truck would turn over but not start. Called a tow truck and he took about an hour to get there. Just before he hooked up I checked ans temp gauge was down to cold. I tried starting the truck and it started but ran rough and I didnt hear any obscene noises from the engine. I am clueless as to may have happened here, has anyone got an idea. Oh yea its a California vehicle if that makes any difference cause of the extra emissions thing. Hopefully I didnt lunch the motor. Attached Images __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " In the end, we only regret the chances we didnt take " " Time is the only currency we spend without knowing the balance, use it wisely ." ..

06-14-2017, 10:37 PM	#2
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,231	Re: 1999 Tahoe Overheat I thought somone for sure would have a thought on this. Well there is antifreeze in the oil but she still runs, but lumpy. Anyway had her towed home and parked her in the garage awaiting a heart transplant. A thought occured to me today that although the engine only had 101,000 miles it was a Fire Dept vehicle so I bet there are mega idle hours on the engine as well. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " In the end, we only regret the chances we didnt take " " Time is the only currency we spend without knowing the balance, use it wisely ." ..

06-15-2017, 12:17 AM	#3
MYTQUIK Registered User Join Date: Apr 2017 Location: PNW Posts: 53	Re: 1999 Tahoe Overheat Sounds like it could be a head gasket issue.

06-15-2017, 07:27 AM	#4
sntrym95 Registered User Join Date: Jan 2006 Location: Big Pine Key, FL Posts: 758	Re: 1999 Tahoe Overheat My initial thoughts are that the green anitfreeze that was added was not the universal type and caused a clog in the cooling system if all of the old antifreeze was not flushed out properly. Other thoughts are that the new tstat stuck closed and caused overheating, there was still air in the system because it wasn't bled completely leading to a bubble near a spot where the gasket edges are close. I would not go straight for the head gasket. Look at the intake gaskets first. If antifreeze is in the oil, it could just be leaking from the intake gasket into the lifter valley. Quick and easy fix. __________________ Mike



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