under-heating problem?

brycerxer · 11-24-2009, 12:27 PM

This one has me scratchin my head: I had a coolant leak on my SE (the hose from the firewall that goes to the driver's side of the engine was leaking). After fixing the leak by cutting an inch or so off the bloated end of that hose and re-attaching, I flushed the system with a garden hose at the top of the radiator with the engine plug removed till it ran clear (lots of crud came out). I also checked the connection at the temp sensor before refilling w/ 50/50, bleeding, etc.

All is well, almost -no leaks, remove all the air bubbles etc. However, the temp gauge on the dash doesn't go nearly as high as it did before. It used to go to a straight down position after full warm up. Now it barely goes beyond the second of the two lines on the cold side, then gets even colder as I drive it.

I'm thinking replace the thermostat first. I hesitate to think its the temp sensor since it worked fine before. What do you guys think? Has anyone else come across this before?

moremazda · 11-24-2009, 10:21 PM

Replace the thermostat just for good measure, but that is where my SE sits even when on track. It would come to the half way point only when the A/C was on in traffic.

RotaryProphet · 11-24-2009, 11:34 PM

I would think after flushing crap out of the coolant system, you would -expect- it to run a bit cooler, no?

rx4ur7 · 11-25-2009, 02:37 PM

Temps are normal now. If a lot of crap came out you possibly cleared out some blockage. You may have also gotten some trapped in the thermostat(sticking open). Back flushing can be good and bad. But you are running normal now. Mine runs in the bottom 1/4 with new radiator and water wetter.

Pro ViZion · 11-25-2009, 04:14 PM

That's where mine is at as well.

brycerxer · 11-28-2009, 07:26 PM

I replaced the thermostat w/ a $10 Duralast from Autozone. The one I took out was shorter- it didn't reach the small hole at the bottom, but the new one does. Cleared out more junk at the radiator hose outlet. Now it warms to just past the second line, then settles back to on that line. Thanks for the input. I didn't realize that was normal. I think I'll do another flush in the near future as this was obviously neglected for a long time.

rx4ur7 · 12-01-2009, 12:20 PM

Well there was your overheat issue. As everyone knows the standard thermostats do not block off the bypass so you do not get full flow through the radiator when it opens. The reason for plugging that hole for racing when you run without thermostat.

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11-24-2009, 12:27 PM	#1
brycerxer The Newbie Join Date: Oct 2008 Location: Phoenix, AZ Posts: 22 Rep Power: 0	under-heating problem? This one has me scratchin my head: I had a coolant leak on my SE (the hose from the firewall that goes to the driver's side of the engine was leaking). After fixing the leak by cutting an inch or so off the bloated end of that hose and re-attaching, I flushed the system with a garden hose at the top of the radiator with the engine plug removed till it ran clear (lots of crud came out). I also checked the connection at the temp sensor before refilling w/ 50/50, bleeding, etc. All is well, almost -no leaks, remove all the air bubbles etc. However, the temp gauge on the dash doesn't go nearly as high as it did before. It used to go to a straight down position after full warm up. Now it barely goes beyond the second of the two lines on the cold side, then gets even colder as I drive it. I'm thinking replace the thermostat first. I hesitate to think its the temp sensor since it worked fine before. What do you guys think? Has anyone else come across this before? __________________ *'85 RX-7 GSL-SE* Current Driver *'85 RX-7 GS* Current project *'84 RX-7* Parts car-SOLD *'91 RX-7 VERT* SOLD Last edited by brycerxer; 11-24-2009 at 12:30 PM.

11-25-2009, 04:14 PM	#5
Pro ViZion Run DAMN YOU!!! Join Date: Nov 2009 Location: Las Vegas, Nevada Posts: 11 Rep Power: 0	That's where mine is at as well. __________________ www.VegasRotary.com - Vegas' local rotary car community!

11-28-2009, 07:26 PM	#6
brycerxer The Newbie Join Date: Oct 2008 Location: Phoenix, AZ Posts: 22 Rep Power: 0	I replaced the thermostat w/ a $10 Duralast from Autozone. The one I took out was shorter- it didn't reach the small hole at the bottom, but the new one does. Cleared out more junk at the radiator hose outlet. Now it warms to just past the second line, then settles back to on that line. Thanks for the input. I didn't realize that was normal. I think I'll do another flush in the near future as this was obviously neglected for a long time. __________________ *'85 RX-7 GSL-SE* Current Driver *'85 RX-7 GS* Current project *'84 RX-7* Parts car-SOLD *'91 RX-7 VERT* SOLD

01-04-2010, 09:29 PM	#8
yellowstonepart Guest Posts: n/a	Yellow stone diesel parts plant is one of the leading manufacturers Yellow stone diesel parts plant is one of the leading manufacturers of engine parts, in particular diesel fuel injection system accessories for replacement, such as Fuel injection Nozzle, Plunger and Delivery valve, ETC In south of china . for more detail please visit our website : www.yellowstonediesel.com www.dieselinjection.cn Yellow stone diesel parts plant was founded in 1997.Over the years, Yellow stone has grown and gained a reputation for producing high quality products and delivering them on time.

11-24-2009, 10:21 PM	#2
moremazda shookmotorsports.com Join Date: Apr 2008 Location: Rockford, IL Posts: 108 Rep Power: 18	Replace the thermostat just for good measure, but that is where my SE sits even when on track. It would come to the half way point only when the A/C was on in traffic.

11-24-2009, 11:34 PM	#3
RotaryProphet Rotary Fanatic Join Date: Sep 2008 Posts: 147 Rep Power: 17	I would think after flushing crap out of the coolant system, you would -expect- it to run a bit cooler, no?

11-25-2009, 02:37 PM	#4
rx4ur7 Rotary since 1972 Join Date: Nov 2008 Location: Tucson Posts: 231 Rep Power: 17	Temps are normal now. If a lot of crap came out you possibly cleared out some blockage. You may have also gotten some trapped in the thermostat(sticking open). Back flushing can be good and bad. But you are running normal now. Mine runs in the bottom 1/4 with new radiator and water wetter.

12-01-2009, 12:20 PM	#7
rx4ur7 Rotary since 1972 Join Date: Nov 2008 Location: Tucson Posts: 231 Rep Power: 17	Well there was your overheat issue. As everyone knows the standard thermostats do not block off the bypass so you do not get full flow through the radiator when it opens. The reason for plugging that hole for racing when you run without thermostat.