Blown Head Gasket? 99 LS1 SS

**Staggart** · 03-16-2011, 02:21 PM

Hey I am a usual creeper on this board but usually never post. I am worried that I have head gasket problem. The reason why I am worried about this is due to a problem starting 5 days ago. It started from a leaky radiator drain plug that continued to leak. I kept an eye on it and kept filling the radiator whenever it appeared to be low, and never ran it hot and it was always full at the time of start-up. I changed the transmission fluid and flushed it about 3 days ago and put a new drain plug on it and thats when I noticed it started to run hot.

Once this happened according to the gauge the motor appeared to run hot. Gauge read around 220-230. I had enough and took it into a radiator place today not wanting to deal with it anymore since it is my DD and it being an aluminum block. I take it in and it reads hot, yet when the shop guy used his ?laser temp gauge? around the radiator, the block, the thermostat, it read no hotter than 150. This surprised the guy and asked if I was leaking any fluid and I told him no, the radiator was changed at around 115K and in fact it was still full when he opened the cap. He then put a funnel in the radiator and filled it up. I started the car and the fluid kept rising. Apparently this is a sign of a small leak in the head gasket causing the system to be pressurized. There is no knock, and the oil is clean. Being military I cant call in sick, I need a car so my questions are-

1. Is the mechanic right?
2. Is it a absolute no go to drive?
3. Is it a bad idea to use stop leak products?
4. Time to rebuild motor soon, as in now?

Thanks.

edit: car has 165,000 miles on it

**Wesman** · 03-16-2011, 04:49 PM

Originally Posted by Staggart

Hey I am a usual creeper on this board but usually never post. I am worried that I have head gasket problem. The reason why I am worried about this is due to a problem starting 5 days ago. It started from a leaky radiator drain plug that continued to leak. I kept an eye on it and kept filling the radiator whenever it appeared to be low, and never ran it hot and it was always full at the time of start-up. I changed the transmission fluid and flushed it about 3 days ago and put a new drain plug on it and thats when I noticed it started to run hot.

Once this happened according to the gauge the motor appeared to run hot. Gauge read around 220-230. I had enough and took it into a radiator place today not wanting to deal with it anymore since it is my DD and it being an aluminum block. I take it in and it reads hot, yet when the shop guy used his ?laser temp gauge? around the radiator, the block, the thermostat, it read no hotter than 150. This surprised the guy and asked if I was leaking any fluid and I told him no, the radiator was changed at around 115K and in fact it was still full when he opened the cap. He then put a funnel in the radiator and filled it up. I started the car and the fluid kept rising. Apparently this is a sign of a small leak in the head gasket causing the system to be pressurized. There is no knock, and the oil is clean. Being military I cant call in sick, I need a car so my questions are-

1. Is the mechanic right?
2. Is it a absolute no go to drive?
3. Is it a bad idea to use stop leak products?
4. Time to rebuild motor soon, as in now?

Thanks.

edit: car has 165,000 miles on it

First...find a new mechanic. That guy obviously doesn't have a clue.

Cooling systems operate on the principle of pressure, thats what prevents the fluid from boiling. The water pump pressurizes the system. When you fill the radiator and start the engine, the fluid level will remain steady while air is being purged out (you'll see bubbles) and then begin to rise once the air is out of the system. It will start to overflow, and at that point you put the cap back on and tighten it down.

I highly doubt you have a blown head gasket. Also, shooting a laser thermometer at the block is not an accurate way to see the actual temperature of the engine, it merely gives you the temp of the surface it is pointed at.

220-230 is definitely on the high side for engine coolant temp, ideally you want to be at about 220 at the highest while the car is idling, and around 195 while driving down the road. Thats with stock t-stat and stock fan settings.

By changing to a 180 degree thermostat and using a tuner to have the fans turn on at 190 degrees, you can make the car run much cooler, which is better for power but slightly worse for emissions.

I wouls start by replacing the thermostat and see if that helps bring it down to a more reasonable temp.

**tep98ws6** · 03-16-2011, 06:07 PM

Have you changed your coolant lately? I had a similar prob after I replaced my water pump and I had a large air bubble ... after it finally burped out, things went back to normal. Definitely check that & your thermostat... also check your engine coolant temperature sensor, it'll cause your temp to act erratically with bad signals being sent to it from the pcm

**jason.d.gantt** · 04-15-2011, 09:14 AM

all good advice...if you changed your coolant, you may have to burp the system, i personaly squezze the upper hose to work out bubbles while it's runnin.

**black2kSS** · 04-15-2011, 09:42 AM

most likely an air pocket in the system. if you say the drain plug on the radiator was leaking some. all those little drips translate to little bubbles in the system. been a mechanic for 12 years and all cars make the coolant push up when you start them. its a result of the surge of coolant from the water pump. usually it will get to a point where it starts to push bubbles out and then level out for the most part unless you rev the car up.

**Mystic Z-28** · 04-16-2011, 03:12 PM

You might just need a new radiator cap. Only about $5 at a parts store. Your cap might be losing it's ability to release pressure. It's actually recommended that you replace your cap once a year.