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Bombtek 12-01-2013 06:25 AM

Bad thermostat?
Ok folks, I have a question that I wasn't able to find the answer to in the forums and its an issue no one else I've spoken to has heard of.

Yesterday morning I after about 15 minutes on the interstate, heater on LOW, I noticed that my temp gauge was very close to pegged *AKA visibly watching it climb, then watched it drop*. I cranked the heater till the next exit and the gauge dropped back to the normal area. I kept going since it's deer season. On the way home, the temp gauge was fine for the first 20 miles then did the same thing. While it is kind of neat to adjust the engine temperature by changing the heat, driving with it set on 90 sucks.

My fluid is a little low, but within the lines. I have no idea how old the fluid it since I've had the car for 3 months. I am thinking it is the thermostat and have already gotten a new one. Does anyone have any other ideas before I tear into this thing?


btstarcher 12-01-2013 06:30 AM

So you kept driving it, even though it overheated? Hopefully the head isn't warped. Next time pull the fuck over and figure out what's wrong.

I'm guessing that the cooling system wasn't burped properly or thoroughly. An evil sonofabitch on these cars. Was the coolant flushed recently?

Bombtek 12-01-2013 06:37 AM

So you kept driving it, even though it overheated? Hopefully the head isn't warped. Next time pull the fuck over and figure out what's wrong.

Not to first car with an AL head that I've seen get hot. Difference between hot on the gauge and over heated. Also when its a fast spike like this was, its no worth than stop and go traffic in the summer time.

I'm guessing that the cooling system wasn't burped properly or thoroughly. An evil sonofabitch on these cars. Was the coolant flushed recently?[/QUOTE]

Driven the car of 3 months, close to 2K miles and this is the FIRST time its done anything out of the norm. I doubt it needs burped. If I had just bought it or it had just been flushed, different story.

btstarcher 12-01-2013 06:40 AM

Ever used the heater before today? Where are you located?

EDIT: I suggested burping because you mentioned "heater." It's sometimes overlooked when burping the coolant to turn the heater on and get rid of the air trapped in the heater core. Mine was burped properly, but not for long enough, and I overheated the first time I used the heater. It took over 2 hours to get all the air out.

Bombtek 12-01-2013 07:57 AM

2Hours! Holy crap. No i have used the heater and driven the car with it off as well in central VA. Just warmed it up and was able to check stuff out. The reserve lines are both ice cold with the car running. I think the heater core was basically acting as a second radiator.

Agent_Orange 12-01-2013 08:32 AM


Originally Posted by Bombtek (Post 2361573)
I kept going since it's deer season.

I gotta ask, WTF does this have to do with anything?

Were you afraid of getting mugged by deer?

btstarcher 12-01-2013 08:56 AM

Living in Arkansas I think I know exactly what he meant....even though I don't hunt, there are fellas here who will drive through any and all kinds of weather under any kind of circumstances just for the opportuniity to kill that one buck.

He Hate Me 12-01-2013 09:10 AM

I want to see pics of the deer strapped to the roof.

Bombtek 12-01-2013 05:28 PM

So far with my luck deer hunting this season, the size of the vehicle isn't a problem. I was also meeting a friend so the deer would have been in his truck. Besides, the size of a deer here, I could quarter it and place it in a tote with no problem.

08cosmic3 12-01-2013 06:10 PM

Thermostat failure is a very common issue in the 1st gen's, not sure about the PU's. I replaced mine a few months ago. The part is cheap but it's a PITA to replace due to where it's located.

Replace the Thermostat, that's most likely the problem unless you are just low on coolant.

div2 12-01-2013 09:21 PM

Exactly- mine failed open a couple of weeks ago.

pzr2874 12-02-2013 01:42 AM

Doesn't sound like a thermostat issue ONLY.

Buy an OEM piece if you decide to go that route.

vtekken 12-02-2013 02:37 AM

I've never personally seen a thermostat failure on the mazdaspeed, but I don't think this is your issue. Usually when they are stuck closed, they do not reopen. Your temp drop after continued driving makes it sound like the thermostat is doing the job. Definitely sounds like it needs to be burped though, and check the quality of your coolant while you're at it.

mituc 12-02-2013 05:37 AM

It's the thermostat, you will have to replace it because it's stuck closed.
When you turn the heater and also increase the fan speed that coolant small/short circuit which is going through the head is getting cooled down by the cooler air coming from the outside (the heater is also part of that small coolant circuit).

I drove my car one full week with a bad thermostat and because the heater was always on I never noticed until I got out of the car one day and the front fan was spinning like nuts while the radiator was ice cold.
At that point I got back into the car and connected my Dashdaq to it and saw that while driving the coolant temperature was 105-108-112C/220-225-233F. Obviously O stopped driving the car from that day until I limped to a car shop with a brand new OEM thermostat and a bottle with 2 liters of FL22 in a shopping bag and the heater turned to the max (after 3 miles of driving the ECT was already 85C/185F).

I was lucky because the temperatures during day time were about -2C/28F, someone told me that if the engine coolant temperature gauge in the dash starts moving up there is like 25-30% chances for the head to wrap :(
Since you saw your temp gauge going towards the H side I suggest to keep an eye on the coolant after you replace the thermostat and make sure it doesn't get dirty after a few hundred miles (which would be a sign of soot/oil entering the cooling system).

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