Hey guys. So, i recently bought a 96 civic hatch with b16a2 engine (its called vti in here) and the mechanic just replaced the thermostat, the radiator cap, and the water pump. However, when im flooring it with the warm engine, the temperature starts to decrease, almost to very cold, and after that it just slowly climbs back to operating temperature. My theory is that the aftermarket radiator cap couldnt hold the pressure, and it sucks some coolant from the reservoir. I tried bleeding the air out but no succes. Is my theory possible, or should i look somewhere else?

 

Thermostat could be stuck opened or you got wrong temp thermostat that’s opening too soon once it heats to a certain temperature

 

I dont think that the thermostat stuck open, the engine heats up normally, but there is a possibility that its open sooner, the mechanic said its a good quality stuff (gates i think). Is this something i should really worry about? The car is in good condition and i dont want to ruin it

 

If it really is overcooling, that has to be the thermostat. Nothing else would cause that.

It could be a gauge error electrically related. If the wire to the sensor is loose the gauge will show cold even though the engine is hot.

 

Get to know your thermostat, he probably installed the wrong one. This response is based off of your OP.

 

I believe the gates thermostat are 170* F. Those lower temps thermostat help for track racing.

Stock temp is 180* F. Get you a oem thermostat.

 

OP didn't state whether he bought the parts to the mechanic to install or the mechanic supplied his own parts. This needs to be verified.

 

The mechanic bought all the stuff, he told me just the brand(mentioned earlier) not the exact type

 

Was wondering also why was it in the shop on the first place???? Overheating issues... whole motor swap...

I bet you the mechanic installed the gates thermostat.

OP let us know more details why the car is in the shop.

 

It was for a timing belt/water pump change, and they said its better to change the thermostat too

 

I had a b18a1 teggy and I was wondering like you also why does the needle moves to cold while driving then sitting idle it’ll raise back to normal temp.
Then found out it had aftermarket thermostat. I changed it back to oem specs thermostat and ran normal. Then I sold it.

But having a thermostat that doesn’t let the engine warm up to normal operating temperature can affect the fueling map, the ecu reading the engine isn’t warmed up properly and it’ll throw more fuel in.

so if I were you I’d get him to change it back to oem specs.
But it’s your choice.

 

duh duh DDDDUUUUHHHH

 

Thanks guys for the help, i just ordered an OEM one, but its a good 1-1,5 months until it gets here, until that, should i use my car?

 

Where the F did you order one from?

 

Amazon, there is nobody selling OEM thermostats in my country. Barely any OEM parts

 

Sucks

 

I think I had one layin around I could have hooked you up.

 

Update:
Just got the OEM thermostat installed. It didnt solved the problem. Any ideas?

 

Have you done no other research in the month you've been waiting? What a waste of time.

 

I hope this save you a huge headache.
When my car had this exact same problem, it was the sender on the head.
It was faulty.
AND!
The only sender that is correctly calibrated is oem Honda. All aftermarket pieces will send incorrect readings. As soon as you start the car it will show over heating.
So pull one from a junk yard.

 

Did the thermostat come with a gasket?

 

Yes

 

You ordered from Amazon.

Did this thermostat come in a sealed Honda parts bag?

Something that looks like this but with your part number?

 

my theory is that the system wasn't bleed completely the 1st time.

 

Yea but air pockets send an overheating signal. Should try changing the sender.