Let me start off with:

1) I have spent several hours searching and reading the overheating topics in this forum.
2) I have read aaroncakes overheating FAQ
3) I have 2 identical 88 verts.

On to the problem.
The other day I noticed the temperature gauge starting to climb rapidly while the car was running down a long hill. It was in gear and turning about 2500 RPM. The temp gauge seemed to just shoot up into the TOP of the gauge.

I pulled over and checked:

1) Belts
2) Fluid level.

Everything seemed OK, so I started driving and the temp dropped right down to lower quarter where it always has been. Noticed after that if the engine was coasting the temp would rise, suddenly, but if I put throttle to it, the temp would come down to where it should be!

After searching the forum I did the following:

1) Changed the fan with the one from the second vert. First one showed same symptons, second vert stayed fine.

2) Replaced thermostat. Yeah I know I should use Mazda, but I got one from Advanced because I could, symptoms didn't change.

I don't lose fluid. The overflow bottle doesn't overflow. There are no bubbles inthe radiator while it is running.

Could it be the temp sensor? If not, what else?

Any and all help would be most appreciated.

 

It could be the sensor taking a dump, or it could be the water pump is starting to take a dump (less water circulation at low RPM). But, doubt the latter as when coasting there is not that much load to cause heat build up.

Keep in mind, the temp sensor is a grounding affair, the hotter the engine the more grounding signal the guage see's. So, perhaps you have a bare wire somewhere that is shorting out sporatically with engine movement.

 

Thanks. I'm going after the sensor this weekend. It's nice (a luxury) having two identical cars to swap parts back and forth. BTW, the water pump has less than 2000 miles on it. Bought it new from Mazdatrix at the beginning of the summer.

 

Perhaps it is a bad radiator, how old is it?

 

It's the original radiator. Just didn't seem like the symptoms fit a plugged radiator, but since nothing else seems to make sense at this time, it's worth a go.

Thanks.

 

My 87 accord does the exact same thing. When I smack the gauge pod the needle returns to normal.

The stock gauges are worthless anyways, I suggest you invest in a aftermarket temp sensor and gauge.

 

I'd put money on the waterpump myself. You get bad parts sometimes, its no ones fault really. THe engine isn't cooling off on its own THAT fast. SHould take a good 20-30 minutes to come down from its perch, and even then maybe not all the way to 1/4.

It could be a temp sensor issue, that's easy to check/replace, check the shop manual.

In the area of replacing cheap parts to see what it does, replace the radiator cap.

 

water pump or radiator core is clogged.

and your bump jjfitzy has been deleted. Bumps are forbidden here in the 2nd gen RX-7 technical section.

 

Even if you have a vaild problem and your thread has been pushed back 3 pages because of threads like.

"How to make my N/A to Turbo"
"Look what UPS brought me"
and
"I'm blowing smoke, is my motor blown"