I recently did a major service including replacing the thermostat and coolant. I bypass the temp board years ago. I have always used a 180F stat being here in Florida and the gauge has run under the midline mark. Whether in traffic, stopped or driving freeway speeds it runs constant. For the past week or so, it's been a needles width above the midline mark. Today waiting at a light with the outside air temp at about 65F, I decided to turn the heat on full and kick the fan on full. I suffered for about a minute and within 15 seconds, the needle came down. Do I have a problem with my new thermostat or something else?

Thanks for looking.
--
'86 sedan with 405,000 miles on the original engine and automatic transmission

Related question - is there a seal between the thermostat housing and the engine block? Or is the seal done just by the O-ring that comes with the thermostat?

As far as draining the coolant to swap the thermostat, do you have to do it with the drain nozzle on the left side of the block under the exhaust manifold or would it be easier to drain some by disconnecting the bottom radiator hose?

Thanks.

Seems like something's wrong. Did you check the t-stat in hot water? Did you pressure test? Belt tension? The car should be able to idle in 100F weather for an hour and a half and not overheat. I wouldn't run an 82C t-stat. Either 87C or 92C. I've always run 87C here in Socal.

Post back.
--
1986 Volvo 245

When I had ordered all my parts from eEuroparts.com, I had forgotten to order one of theirs with the vent hole and picked one up from Autozone that did not have the hole in it. Usually I'm careful with those issues. I guess I should get the correct one.

Thanks for the reminder.
--
'86 sedan with 405,000 miles on the original engine and automatic transmission

You could drill a small hole in the lip. I don't think it's getting hot enough to worry about.
Dan

I'm going to say you are fine the new thermostat is just a bit different than the old one. Keep an eye on it for awhile. Did you instal the new thermostat with the hole straight up?
Dan

I don't think you can install a t-stat upside down, it doesn't fit in the housing.I just checked last week 'cause I wasn't sure if I had it in right.

You are correct you can't install one upside down but you can rotate it 0 - 360 degrees. The hole on the thermostats lip needs to be straight up. This is the highest point of the cooing systems, the hole allows you to fill it all the way up without an air bubble. Dan

Hi All,

I thought I'd mention something a retired mechanic once suggested to me to help restore cooling system efficiency. He said it's a good idea to periodically check and clean away any dirt and/or road debris that may be clogging-up the cooling fins in both the radiator and a/c condenser. This can be done by either shooting water with a garden hose or shooting air using an air compressor, using the procedure described below:

NOTE: WHEN DOING THIS PROCEDURE, BE CAREFUL NOT TO DAMAGE THE COOLING FINS AND RADIATOR TUBES WITH YOUR NOZZLE, AND ONLY DO THIS WITH THE ENGINE OFF!!!

Make sure the engine off, and preferably cold. Open the hood and remove the front grill. Reach down between the radiator and fan, and point your nozzle (air or water) towards the grill (i.e., away from the engine), and begin shooting. This way you are cleaning in the opposite direction from when the debris first entered the cooling fins. By doing this procedure, you may wash away leaves, dirt, bugs, etc., and help your radiator dissipate heat.

Alex