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Engine Specific Info and Questions => IDI Engine => Topic started by: 92EcoDiesel Jetta on August 25, 2011, 02:07:31 pm

Title: Coolant temp gauge reading is lower after new head gasket
Post by: 92EcoDiesel Jetta on August 25, 2011, 02:07:31 pm
The temp gauge used to read a little above the middle mark when I had a leaky head gasket. After installing a new head gasket, the temp gauge now reads quite a bit lower in all instances (idling, hwy). Is this normal? Did the combustion gas (which is much hotter than colant) leaking into the cooling system actually raised the coolant temp thus raising the temp gauge reading or do I still have air in the system?
Title: Re: Coolant temp gauge reading is lower after new head gasket
Post by: silentdub on August 26, 2011, 12:55:31 pm
I assume you flushed the coolant during the job, maybe fresh coolant? New Thermo? Maybe you cleared away from crap from the sensor?

All play a factor, if you did flush it, maybe there was a blockage in the rad which is no longer there.


Title: Re: Coolant temp gauge reading is lower after new head gasket
Post by: RadoTD on August 26, 2011, 01:21:55 pm
Did the combustion gas (which is much hotter than colant) leaking into the cooling system actually raised the coolant temp thus raising the temp gauge reading

Yes, if your head gasket was blown between the cylinder and water jacket, this would happen.

When all is well, these engines tend to run quite cool! Anything under 15*C if I'm actually moving, my thermostat doesn't open
Title: Re: Coolant temp gauge reading is lower after new head gasket
Post by: nathan_b on August 26, 2011, 01:45:49 pm
Last winter I got my truck up to operating temperatures within 5 miles, I stopped and let it idle when itt was about 10f and it went all the way cold. haha
Title: Re: Coolant temp gauge reading is lower after new head gasket
Post by: R.O.R-2.0 on August 27, 2011, 12:45:32 pm
Last winter I got my truck up to operating temperatures within 5 miles, I stopped and let it idle when itt was about 10f and it went all the way cold. haha

i had my car almost over heating by the time i got to the top of the mountain i was going over, then i crested the peak, and oh boy, didnt take it long before the needle was buried clear back on the cold peg..
Title: Re: Coolant temp gauge reading is lower after new head gasket
Post by: 92EcoDiesel Jetta on August 27, 2011, 03:15:40 pm
Yes 2 flush with water only, no chemicals, same thermostat. I filled it with water and got the engine to operating temp (fans cycled= thermostat open) then pulled the hose off the thermostat housing and that drained the system in seconds. I let the engine cool overnight and repeated the procedure then filled with G12.

I assume you flushed the coolant during the job, maybe fresh coolant? New Thermo? Maybe you cleared away from crap from the sensor?

All play a factor, if you did flush it, maybe there was a blockage in the rad which is no longer there.