Hey guys,

vehicle: 1998 Honda Civic LX
engine: D16Y7
Miles: 260,000+

To preface this I just want to say I am new to this forum. I am a mechanic, and just wanted some advice/war stories to see what my issue could be. The vehicle over heated and I narrowed it down to a stuck thermostat. (top rad hose was hot, bottom was ice cold) I replaced the thermostat (and gasket) with a new Murray from AutoZone (yes I made sure the little jingly bit to let air bubbles past was facing UP and the gasket is not obstructing it) (and yes I put the T/S in the correct way) I start the car uphill, leave rad cap off, heater on full blast, and add coolant as needed. Car gets up to temp. I start driving and the coolant gauge rises. Park it, feel the hoses and what do you know, top is hot and bottom is STILL ice cold. The NEW thermostat is not opening. Now before it over heated I have replaced the following:

• cylinder head (was rebuilt and decked, put in with arp head studs and copper cometic gasket)
• water pump
• ECT sensor
• ECT sender sensor (for C/H gauge in car)
• ECT fan switch (mounted to T/S housing)
• radiator (brand new, no leaks)
• all coolant hoses (verified NO leaks)

Basically every single thing that can be replaced, was replaced. Anyways, I take the thermostat out of the car, and bolt the T/S housing back up to the car with NO thermostat. I start the car and it gets up to temp. I drive it down the road (70 mph) and it DOES NOT overheat once. I check the top & bottom rad hoses, and they池e BOTH hot this time.

I then take the thermostat inside my house and put it in boiling hot water, and it opens just fine. I did it several times and visually saw it open and then close back up when I took it out.

At this point I知 at a little loss for words because I have heard of people who got defective T/S痴 before. And this thermostat is an OEM 170 F one.

Any advice you guys have would be great. I know running the car without a T/S isn稚 the best because it puts more wear and tear, but I ordered a new one from rock auto, so I知 going to do that until it gets here.

Thanks.

 

Sounds like an air pocket to me.

Cut the jiggler off and just leave the small hole.

A funnel bucket is also very helpful.

I have gone through all of that and still had to get them up around 220-230 to get the stupid thermostat to open that first time. Usually holding the revs up around 3k helps.

Never tried a vacuum fill. Not sure if that would eliminate the issue or not.

 

I'll try what you mentioned. I appreciate it.

 

Murray is NOT the OE Manufacturer... I suggest you get a GENUINE thermostat from the local Honda parts department. The most common issue created with aftermarket thermostats compared to the OEM thermostat is that the rear end of the unit does not control coolant flow through the bypass circuit properly and this frequently causes overheating issues.

 

Yeah, I knew it wasn't the OE one, but I was in the mindset that this car has been out long enough, you'd think that getting a replacement part from places like AutoZone would be fine because they would have all the kinks worked out with the parts and whatnot. I guess not. I ordered an OEM replacement one, so I'm just waiting for it to come in. Thanks for your insight.

 

How high does the temp gauge go, above half way is okish, just dont let it go all the way to the red. What is the temp of the City that you are working on the car (Cold area, it will take a while for the car to properly warmup) ? Turn off the heater fan and let the car idle for 30 minutes if its below 30F outside, These little 4 bangers for some reason take forever for the t-stat to open.

 

it goes all the way up to H. Temp of San Antonio is around 77 degrees. It doesn't take long at all. It was 90 degrees yesterday. The thermostat just refuses to open.

 

not being a wise a## here, Are you putting it in the right way?