mk1 1.6 thermostat replacement
Discussion
Pretty sure the thermostat is stuck wide open on our 1990 Eunos so going to replace it.
Was going to go with the MX5 Parts (non OEM) kit that comes with seal unless anybody suggests otherwise.
Looking at it, it looks like I should be able to do the job without replacing coolant, can anybody confirm that is the case?
Was going to go with the MX5 Parts (non OEM) kit that comes with seal unless anybody suggests otherwise.
Looking at it, it looks like I should be able to do the job without replacing coolant, can anybody confirm that is the case?
You can do it without replacing the coolant - but you will need to drain it. Handily, in the middle bottom of the radiator is a plastic threaded plug, just remove this with a large phillips screwdriver with a clean bucket underneath. Your choice as to whether to drain off a bit or all of it, makes no real odds in my opinion. Take the cap off the rad (afterward) and the coolant will flood out. (By the way, you don't even need to remove the undertray, Mazda kindly provided a hole in it for just this purpose.
If the antifreeze is a few years old - then replace it - Mazda rads are prone to sludging up and also the combination cast iron/alloy construction of the engine won't take kindly to poor corrosion protection.
Don't mix antifreeze types either, I did and managed to make a very large, hard to access blancmange in my cooling system. I would stick to the older type in mine (not a bright pink/orange colour). If you are changing types flush out the old thoroughly.
Lastly (sorry - I do go on) - the hard part of this job is actually the refilling. Make sure that the exopansion reservoir (drivers side inner wing) is filed up to the correct level first. Then slowly fill the engine from the radiator top. Make sure the heater is in the HOT position. Once it's filled to the top, start the engine and let it idle up to temperature, keeping an eye on the level in the rad. At some point (as the stat opens) it will suddenly drop, fill back up to the top of the cap and refit the cap. It should now be bled, but as a final check make sure the top rad hose gets hot, same for the top of the radiator across its width, and also that the heater hoses are hot (in fact, check that the heater gives nice hot air). For the next few trips just check the expansion tank level is okay, and keep an eagle eye on the temp gauge.
Lastly - ONCE ITS HOT NEVER TAKE THE RADIATOR CAP OFF. This thing can fire hot coolant a fair way!
Sorry again if this is telling grandma how to suck eggs...
If the antifreeze is a few years old - then replace it - Mazda rads are prone to sludging up and also the combination cast iron/alloy construction of the engine won't take kindly to poor corrosion protection.
Don't mix antifreeze types either, I did and managed to make a very large, hard to access blancmange in my cooling system. I would stick to the older type in mine (not a bright pink/orange colour). If you are changing types flush out the old thoroughly.
Lastly (sorry - I do go on) - the hard part of this job is actually the refilling. Make sure that the exopansion reservoir (drivers side inner wing) is filed up to the correct level first. Then slowly fill the engine from the radiator top. Make sure the heater is in the HOT position. Once it's filled to the top, start the engine and let it idle up to temperature, keeping an eye on the level in the rad. At some point (as the stat opens) it will suddenly drop, fill back up to the top of the cap and refit the cap. It should now be bled, but as a final check make sure the top rad hose gets hot, same for the top of the radiator across its width, and also that the heater hoses are hot (in fact, check that the heater gives nice hot air). For the next few trips just check the expansion tank level is okay, and keep an eagle eye on the temp gauge.
Lastly - ONCE ITS HOT NEVER TAKE THE RADIATOR CAP OFF. This thing can fire hot coolant a fair way!
Sorry again if this is telling grandma how to suck eggs...
neil_bolton said:
With stuff like that, unless the part is drastically more expensive, I'd go with the Mazda part.
Especially so with Electrical sensors...
I'd agree with that. For the price I'd go for the Mazda part for thermostat and rad-cap.Especially so with Electrical sensors...
What makes you think the 'stat is stuck open?
MX-5 Lazza said:
neil_bolton said:
With stuff like that, unless the part is drastically more expensive, I'd go with the Mazda part.
Especially so with Electrical sensors...
I'd agree with that. For the price I'd go for the Mazda part for thermostat and rad-cap.Especially so with Electrical sensors...
What makes you think the 'stat is stuck open?
The reason I think its stuck is that the car is taking an age to get any kind of heat into the coolant and rarely gets much above a quarter on the temp dial. Heater is only firing luke warm air out. Has been gradually getting worse over last few days.
A quick thanks to FranV8, really appreciate that.
CaptainSlow said:
Just having a problem with my 1.6 mk1. Will a faulty thermostat stop the rad fan activating.
Unsure if my thermostat is faulty but the top hose gets warm rather than hot and the top of the radiator doesn't get hot, but the car overheats.
Well now it started for 30 seconds and then cut out, twice. Now cranks but won't start. Would a faulty water temperature sender do this and if so an easy way to check?Unsure if my thermostat is faulty but the top hose gets warm rather than hot and the top of the radiator doesn't get hot, but the car overheats.
Don't quote me on this, as its purely a guess. But sounds like a coolant temperature sensor fault, my understanding is that they increase fuel delivery when the engine is cold to aid starting, if the sensor thinks the engine is hot it may not be chucking enough fuel in to start the engine.
Not sure if the sensor runs the fan, but it would explain why it is always running.
Not sure if the sensor runs the fan, but it would explain why it is always running.
If the sensor on top of the thermostat (on the 1.6) fails then the fan wont kick in. You can prove the theory by diconnecting the sensor and grounding the wire. On mine the whole connectro had broken down, when i tried to "give it a wiggle" it snapped clean in half!
This happened to mine 18 months ago - it led to the fan not switching on and the car slowly overheating when engine running and car not moving.
Fwiw i replaced my thermostat (seperate issue to the one above) with the cheap aftermarket part. It was about £8 and as i recall it did have the little jiggle valve thing. Its been fine to date. I was feeling particulary cheap that day though, and would normally choose OEM.
This happened to mine 18 months ago - it led to the fan not switching on and the car slowly overheating when engine running and car not moving.
Fwiw i replaced my thermostat (seperate issue to the one above) with the cheap aftermarket part. It was about £8 and as i recall it did have the little jiggle valve thing. Its been fine to date. I was feeling particulary cheap that day though, and would normally choose OEM.
Gassing Station | Mazda MX5/Roadster/Miata | Top of Page | What's New | My Stuff