I'm having cooling issues with my car and I'm systematically trying a series of possible fixes to see if I can solve the problem without going all out to buy a new radiator. Basically, it runs way too hot (according to my temp gauge; commonly runs at 3/4 to 7/8 unless it's really cold outside).

Really big aggrevators are hot days and freeway speeds.

I've gotten a coolant flush, new filler and radiator caps, and made sure the fins were clear and not too flattened.

I had a thermostat put in by a "Mazda specialist" - Damn moron used an aftermarket Stant thermostat and charged me $71 for it. Well DUH it's not gonna solve the problem (from what I've read from lots of people on this forum), and now he wants to put a new radiator in there for $350 without even checking other less expensive possible causes. But I was naive at the time and didn't know everything I should have.

So I'm gonna do the tedious investigation on my cooling system myself.

First thing I did was to order a Raytek laser thermometer ($65 on Ebay +shipping) so I could have quantitative information that's more precise than "1/2 way up the guage". It hasn't gotten here yet so I can't tell you how well it works.

Does anyone here know what actual temperature, in F or C, the 13B should be running at?

I also bought a bottle of Water Wetter, but can't put it in until my engine is cool (tomorrow morning). Speaking of Water Wetter, should you put in an amount according to the instructions on the bottle, or just pour the whole thing in?

Can anyone tell me how to check my fan and/or its clutch to see if they're working properly, and possible fixes if they aren't?

Anyway, I've ordered an OEM Mazda thermostat from the dealer here ($21) and will put it in myself. If that doesn't solve the problem, I'll see if my coolant temp sensor is bad by putting a new one in and seeing what the guage says.

If that doesn't do it, I want to put on an undershroud that I've heard about from this forum that's supposed to direct incoming air right into the radiator.

Problem is, I don't own or have access to a coolant temp sensor or that undershroud thing. Some kind soul on this forum, wish I could remember who it was, gave me the part number for that undershroud, and when I had the dealer run that number, he told me that shroud was just under $200. Little out of my price range (unless I get desperate).

So does anyone have those parts in good working order for sale? Anyone have any more info/suggestions for me? I've posted threads concerning this problem before, and I've gotten lots of good info. So I've arrived at this plan of action and I'd like opinions on it. Thanks guys!

 

It just so happens that I have an underbody shroud in pretty good shape. Also, which coolant sensor do you need? I have some of those too. Chances are that I will have more stuff you need, since I have a whole 86 I am parting out. Do you have an S4 or S5?

Rat

 

Water wetter: Either dump the whole bottle in(remove some coolant first) or put 10oz in the radiator and toss the rest into the recovery/reservoirbottle/2nd car.... since there is not point in keeping a more than half empty bottle of toxic chemicals. I have always used the full bottle because I am too lazy to open a 2nd hood and never had problems in 10 years of use.

There are several people stripping wrecked/ruined cars here and on ebay. They will either pipe in or you might need to do some searching. Check out the forsale/wanted forums and thepartstrader.

The mechanical fan test: When car is hot(and off), try to spin it. It should have resistance.

Screw the $350 radiator. There are $400-$550 radiators that fit and hold more coolant.


The thermostat opens between 177-182 degrees F.
The thermostat must be fully open by 203 degree F.
Certains models have an electric fan that kicks in at 207F and off at 194F.
edit: 1991 NA FSM specs

 

Go to a few wreckers to find the undertray. Do it first; even if it’s not the main cause of the problem, it’s supposed to be there and its absence won’t be helping. Make sure the plastic shrouds above the radiator are also in place. These are just as important.
Don’t buy a replacement temp gauge sender unless you know it’s at fault. Remove it and test it as per the FSM. If you do replace it, get a new one.
Unless you’re having cooling problems at idle, it’s probably not the fan. Test it anyway, again as per the FSM.
Check for blocked radiator tubes by feeling the temp across the radiator’s top tank. You laser thermometer will be excellent for this. It should have even temps right across.
You may also have corroded water pump impeller. The only way to check this is to remove the pump and inspect it.

 

P.S. I have a water pump too!

 

It should cost you like $50 to take your radatior (out of the car) and have it rodded out, inspected, and cleaned.

James

 

J-Rat: How much would you want for the undershroud, if I can't find one at a junkyward around here? And the coolant temp sensor that I *think* that I *may* need is the one that plugs into the back of the thermostat housing. If I need a water pump, how much would you want for yours, and is it in good shape?

DeadRX7Conv: I just went out and did that mechanical fan test. There's a little resistance... how much should there be? I can tell you that when I gave a hard push using just my fingers (imagine an open hand closing into a fist as fast as possible) in the normal direction of rotation, it went a little over halfway around and stopped. Its angular deceleration was visibly noticable.

If I did end up getting a new radiator, would the Fluidyne be a good choice? $417 online, plus shipping I'm sure.

Will the outside of the thermostat housing be the same temp as the thermostat itself? This is where my soon-to-be-arriving laser thermometer comes into play.

NZConvertible: How exactly do you test the temp gauge sender? I'm sure getting it off will be easy, but I don't remember reading about a way to test it. And is there a way to remove and inspect the water pump and be confident that I'm looking for the right things when I've never done that before?

Wankel7: Where would I take my radiator to have it rodded out like you're saying? A radiator shop? And would that be a guaranteed fix you think?

 

I am rather sure that they will take the end tanks off and inspect the inside of the radatior. Call the radatior shop and ask for what they do. Tell them you have one with plastic end tanks.

But, if it is blocked it being cleared would sure help

Also, have you throughly made sure there is no dirt and debris in the way of the radatior?
They like to pile up and block fresh air.
James

 

That’s the ECU’s coolant sensor, not the temp gauge sender. It will not have anything to do with this problem. The temp gauge sender is on the side of the engine under the oil filter, and has one wire on it. Don't confuse it with the much larger oil pressure sender next to it.When the engine is cold, the fan should move quite freely with only a little resistance. Start the car and let it idle until it warms right up. Don’t let it overheat, if the temp starts to rise above normal then shut it off. Now check the fan and it should be much harder to turn (not solid but very stiff). If it isn’t, it’s shot. That’s not how you test a thermostat. You have to remove it, put it in water, heat the water, and check the temp it opens at. The procedure is in the Cooling System chapter of the FSM. This procedure is also in the Cooling System chapter of the FSM. (If you haven't got it, get it!) It should be pretty obvious if the impeller’s fins are corroded away. If in doubt take it to a mechanic or radiator shop. Maybe someone can post a pic of a good one? Yep.

 

The water pump should be good, its off a rebuilt motor that has only 2k on it. And the underbody shroud is in good shape. I couldnt tell you what they are worth, since I really dont know. If the dealer wants $200, I will sell it to you for $40 plus shipping. The water pump will be $5.

Rat

 

IF you havent bought yet, I should have all these parts. hypntyz@charter.net