hopslover

Detailed Background (Skip to Just the Facts for a more concise rundown)
I bought this car for my son. It has 188k miles on it. We didn't know when the timing belt was last replaced, so I replaced the belt, the balancer belt, the pulleys, springs AND THE WATER PUMP. The new pump looked exactly like the outgoing pump, which looked perfectly fine. We had driven the car approximately 1000 miles prior to the work and had not noticed any issues.

Following the work, we filled the coolant and idled the car for 15-20 minutes with no issues.

My son drove it the next day and reported overheating issues. I saw the same and went through several run/fill cycles with fresh coolant until the system was full. I did attempt to bleed off any air by squeezing the top radiator hose. After this, I drove it it 10 miles on the freeway with no more issues.

My son reported issues again, so we drained the entire system (including the block plug), replaced the thermo, the radiator cap, and refilled the system with a mixture of fresh 50-60% coolant and distilled water, bled air out of the system using both the bleed screw and by squeezing the top radiator hose.

He still reports issues.

"Normal" for this care is about 1/3 up the dial. he says the temp was steady for most of the trip, but very quickly climbed to about 3/4 of the way up the gauge and then just as quickly dropped back to normal. He drove about 10 miles and the outside temp was about 80.

Just the Facts

• No previous issues
• Replaced water, pump, radiator cap, thermostat, drained the radiator and the block, and flushed and filled the system with new coolant/distilled water
• Bled the system using both the coolant bleed screw and squeezing the upper radiator hose.
• Now we have overheating issues.

Observations

• No problems seen while idling car in the driveway.
• Passenger-side fan runs constantly when AC is on, but never when it's off. Driver's side fan seems to never run. There is an occasional groan that seems to come from that area, but the fan never turns on.
• Coolant seems to be escaping out the top of the overflow tank when it overheats (sort of looks like there's a tiny pinhole in the plastic near where the overflow hose connects to the tank). While this doesn't seem normal, I can't believe this leak just started as we hadn't even touched the tank.
• The temperature fluctuations are quick, rising and falling in seconds.

Thanks for your suggestions.

Showmeyourtints

How does the motor oil look? Are your coolant amounts staying the same or are you losing coolant. First thing to check is the motor oil. If it looks like a milkshake you're going to need to replace the head gasket.

hopslover

Thanks. Motor oil looks fine.

Showmeyourtints

Buy an aftermarket mechanical temp gauge. They're pretty straight forward to install or have your mechanic install it. Then you will see what the actual temp is. Could be a faulty sensor. Could be a bad thermostat. Could be the radiator cap. Could be a multitude of things. But getting the mech temp gauge will allow you to see what the temp is and avoid any costly or unnecessary repairs.

hopslover

I'm wondering if the problem is linked to a tiny pinhole in the elbow of the inlet to the coolant overflow tank. When the engine heats up, steam begins to come out of this hole. It seems like this is not allowing the system to pressurize properly.

Showmeyourtints

Well first and foremost coolant should never leak from your vehicle. Ever.

hopslover

Agreed. I've sealed the hole with some 3M adhesive sealant that I use on my boat and the problem has disappeared completely. It's maintaining the coolant level and no more overheating.

I have no idea what caused the hole or how this just happened to coincide with my timing belt swap, but that's got to be what it was.

I've been driving it for the past week with no issues and today I stressed it with a 50-mile mountain drive and the needle never moved off of it's normal position.

I'm pretty sure it still needs a new fan, but we're entering Winter, so I'll put that off for a while. We won't see 70s until at least April.