Overheating issue
Thread Starter
Honda-Tech Member
Joined: Aug 2007
Posts: 300
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From: Midlothian, Va, USA
Overheating issue
Hey Guys,
Just rebuilt my engine over the past year, a6 block with z6 head, replaced the water pump during the process. I still have the stock CRX radiator. The other day I floored it and noticed as I hit a stoplight that the temperature gauge was reading a little high, so I put it in neutral and coasted to the light, and the gauge went down...
Well this morning, on my way to work I have to take I-95 and I was going about 75, and looked down and realized it was super high! I moved into the right hand lane and slowed down to just under 60 and it went down, but then went right back up! I even got off the highway and was going down stoplight roads, and while sitting at the stoplights watched it climb! At points during driving, it would go down, but then climb back up again... As I pulled into the parking lot at work, it finally came close to the redline on the dash, so I shut the car off and coasted it into a parking spot, popped the hood, touched the radiator, not very hot. Touched the valve cover, not hotter than I normally notice. Could this be my thermostat gone bad? From the way the gauge was acting, it seemed to me like the thermostat was opening and closing irregularly... This build has close to 2000 miles on it with a new headgasket, so I do not think that could have been it. Could low oil be it? I checked the oil the other day and it was okay, but I have been leaking a little but since the rebuild. I've also been leaking a little bit of coolant, but not alot. I did top it off yesterday when I put hondabond on the upper hose mount on the head... Hit me with ideas please.
Just rebuilt my engine over the past year, a6 block with z6 head, replaced the water pump during the process. I still have the stock CRX radiator. The other day I floored it and noticed as I hit a stoplight that the temperature gauge was reading a little high, so I put it in neutral and coasted to the light, and the gauge went down...
Well this morning, on my way to work I have to take I-95 and I was going about 75, and looked down and realized it was super high! I moved into the right hand lane and slowed down to just under 60 and it went down, but then went right back up! I even got off the highway and was going down stoplight roads, and while sitting at the stoplights watched it climb! At points during driving, it would go down, but then climb back up again... As I pulled into the parking lot at work, it finally came close to the redline on the dash, so I shut the car off and coasted it into a parking spot, popped the hood, touched the radiator, not very hot. Touched the valve cover, not hotter than I normally notice. Could this be my thermostat gone bad? From the way the gauge was acting, it seemed to me like the thermostat was opening and closing irregularly... This build has close to 2000 miles on it with a new headgasket, so I do not think that could have been it. Could low oil be it? I checked the oil the other day and it was okay, but I have been leaking a little but since the rebuild. I've also been leaking a little bit of coolant, but not alot. I did top it off yesterday when I put hondabond on the upper hose mount on the head... Hit me with ideas please.
EFB055
Joined: Dec 2005
Posts: 13,249
Likes: 14
From: Brisvegas, QLD, Australia
Re: Overheating issue
If you've been leaking coolant then the top radiator tank may not be hot due to it not containing any fluid.
Because it was overheating on the highway you can rule out fan issues.
If you start the car with no radiator cap on, can you see the water circulating? If not there's a blockage or a closed thermostat.
It's not hard to test the thermostat though, remove it and pop it into water and gradually heat it. The thermostat should begin to open at around 70*C and fully open before the water hits boiling point.
But to start with, just make sure you weren't overheating due to low coolant levels.
Because it was overheating on the highway you can rule out fan issues.
If you start the car with no radiator cap on, can you see the water circulating? If not there's a blockage or a closed thermostat.
It's not hard to test the thermostat though, remove it and pop it into water and gradually heat it. The thermostat should begin to open at around 70*C and fully open before the water hits boiling point.
But to start with, just make sure you weren't overheating due to low coolant levels.
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