MY 1988 MAZDA RX-7 CONVERTIBLE OVERHEATS

20

Asked by Jul 17, 2012 at 06:28 PM about the 1988 Mazda RX-7

Question type: Maintenance & Repair

The coolant will not run through the motor, and gets stuck at the pressure valve and boils over. The hoses do not appear to be clogged, and I had a friend of mine look at it, and he removed the thermostat, but did not replace it. This did not change anything. The coolant still gets stuck at the pressure valve and when turned off, returns to the container where it boils out and spews on the pavement.

24 Answers

180

useually one of two things ,water pump is bad or your heater coil is pluged up with rus - is there lots of rus y looking water or is it clean , if clean,,water pump ,,taking out thermostat in this typ of car in not recomended for the fact tha they have aluminum heads and will warp if over heated to much,,we used to do that to to a lot of older cars but there heads are steel ,the thermo can keep you from paying for heads,,,,,you could have a blocked waterway but that is not likely!

1 out of 1 people think this is helpful.
20

thank you, how easy would it be to check the possible problems?

4,755

Are you sure it's actually overheating and not just the radiator cap pressure spring giving out?? If it's actually overheating check whether the waterpump is actually being driven by the fan belt, belt slipping can seriously mess up pump efficiency in FC's, especially when the air pump has been removed and the alternator still uses a single sheave pulley. Replace your water pump if you have any doubt about it (they're about $60 for an aftermarket pump or $100 for an original), it's better safe than sorry as the rotary engine can warp quite quickly when overheating (it has no cylinder head, it's the rotor housings themselves that warp forcing you to either find new housings or a rebuilt engine). While the waterpump is off make sure your radiator and the cooling passages in the engine itself aren't clogged by running water through either part using a hose. Running the engine without a thermostat actually doesn't cause any overheating issues in any car, it's more overcooling due to the water always passing through the radiator and not allowing the engine to reach optimal operating temperature and thus causing poor emissions/fuel economy. The heater matrix shouldn't be an issue either as it receives it's coolant off a bypass at the back of the engine which is outside the main coolant flow of the engine. Also see section 03 of the FSM at http://www.rotaryheads.com/PDF/2nd_gen/Mazda%20Service%20Manuals/1986-88%20Factory%20Service%20Manual/03_cooling_system.pdf

2 out of 2 people think this is helpful.
20

the water pump is not making any noise to give us a reason to think it is that.

1 out of 1 people think this is helpful.
4,755

In that case check radiator and engine for coolant flow restrictions, that's your best bet for now.

2 out of 2 people think this is helpful.
20

thank you!

4,755

Let me know how you fare and make sure you read the FSM.

1 out of 1 people think this is helpful.
35

if you have had or performed work on your coolant system you may have a air bubble blocking the flow of coolant to your block the majority of cars have a bleeder for this on the intake if you need to know how 2 bleed it let me know of if you need more info about it

2 out of 2 people think this is helpful.
20

there was indeed an air bubble thank you for the help! it works perfectly now!

1 out of 1 people think this is helpful.
35

your welcome no problem man

1 out of 1 people think this is helpful.
60

Jonathan/lars...can u help me with that air bubble proceedure? Mine is doing the same thing.. I was going to install a new water pump but my bolt on my bottom pulley was rusted.. my car gets extremely hott very quickly.. I've replaced thermostat already... But water seems to form in my overflow then spill out when I come to a stop.. Plz message me on my facebook for quicker response.. anthonyduceducemiller@yahoo.com

1 out of 1 people think this is helpful.
4,755

Raise the front of the car so the cap is the highest point in the system (jack it up as high as possible). You will need to let the car idle until the thermostat opens to cycle out any air bubbles. Let it cool and top it off.

60

How will I know when thermo is open? I have two brand new caps on a new thermostat and new waterpump.. just replaced stock clutch fan with a big electric radiator fan hooked to a switch in cabin.. and it won't stay cool for more than 10min.. Unless I get on freeway and do over 75.

1 out of 1 people think this is helpful.
60

*and a new thermostat

1 out of 1 people think this is helpful.
60

And by topping it off you mean? Filling radiator with coolant then putting cap back on? Or. Filling radiator then putting cap back on the squeezing hose to push water/air then taking cap off n repeating till its topped off? Lol I know..sounds stupid..but some rotory guy suggested that... Lol

4,755

The thermostat is open when the radiator is hot to the touch. That means coolant is routed through the radiator to cool it. As for the topping off: just wait for the engine to cool and then take the cap off, add coolant as required and repeat. Squeezing the radiator hose to dislodge air bubbles helps sometimes but in my experience cycling the engine twice like this gets 99% of the air out.

60

So.run car till warm.turn car off.wait till cool. Add coolant till its full(in radiator) repeat 1-2x? Ok.got it. Also was told to take cap off start car n let it warm up then add that way.. but ur way sounds the way to go. Thanks again bud. I hope this works.. if it doesn't then I'm prob faced with a bad seal.. :( I just got this car 2-3 weeks ago.. ran fine on way home.. 3+ hr drive. Smh..

1 out of 1 people think this is helpful.
4,755

Make sure it's well nose-up, so the air can make its way to the radiator easier.

1 out of 1 people think this is helpful.
60

Ok. My drive way has a big incline.. ill park it front up so it tilts backwards.. Thanks again..!

1 out of 1 people think this is helpful.
4,755

Good luck and enjoy the rotary fun!

1 out of 1 people think this is helpful.
60

One last question. If my overflow is full should I drain it before I do the proceedure?

1 out of 1 people think this is helpful.
4,755

Fill it, any real excess coolant will be dumped out of the overflow bottle air will also escape through there but coolant will be sucked in again once the air is expelled.

60

Ok.. I did it 3-4 times.. it still gets extremely hot.. Bad coolant seal?

4,755

Possibly one of the new items (water pump, thermostat, cooling fan or radiator caps) is not working as advertised, or you may have clogged coolant passages in the engine and/or or radiator. Did you put the thermostat in the right way round?

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