OVERHEATING FOR 9 MONTHS - Impossible diagnostic?

[Guran]

Just ditch the thermostat and try running without one. It eliminates any question about potential sticking and flow restriction from the thermostat. If your overheating problems go away, then you know your new thermostat was sticking and not opening fully at temperature. If it doesn't go away, then you can look at other potential sources of flow restriction.

I have had endless problems with thermostats. One of them cost me an engine. I've had three brand new genuine Mazda replacements (one in NA, one in NB, one in NC) that immediately had issues with sticking ... either not opening fully (causing overheating), or not closing fully (car takes forever to get up to temperature and/or heater blows cold air).

[bruce]

Yes, try ditching the thermostat for a while. If faulty it will run cold and take ages to get to temp. If it overheats, move on and pull the last of your hair out.

[Skifey]

You need to understand that the replacement radiator may be faulty and must be checked. Driving a car and overheating is a big no no.

I don't disagree with you at all I do however doubt it is the problem as it was overheating with the EXACT same symptoms before and after the replacement Mishimoto radiator was put in. Regardless Is there a way to diagnose a faulty radiator without dropping the coolant? I've changed it 4 times and I really don't wanna throw another $40 at coolant.

I'm confident it's overheating because the coolant overflow reservoir (when it's full which it currently isn't) will boil during the overheating.
How can I test that it's pressurizing myself? I believe the mechanic checked this and said it was 100%
He's probably wrong. A good mechanic or coolant specialist can check it. Check this out. It is one method. https://www.youtube.com/watch?v=2C4R96icPpI


How do I bypass the heater? I imagine there's a little guide somewhere? Take a length of heater hose. Attach it to the heater outlet at the back of the engine and loop it around and attach the other end to the heater inlet on the rear of the engine. The heater is no longer attached and is bypassed. If the heater is blocked then coolant wont circulate and just boil. If it doesn't overheat with the bypass hose in place then you definitely have a blocked heater core. Its one way to eliminate a possibility.

Hope this helps.

Anything and everything is helpful at this stage; I appreciate it <3
On this note; does anyone have a reliable and knowledgable cooling specialist that they would recommend in the Brisbane Area?
Also, the heater is definitely blowing hot air, does this rule out the possibility of a block heater core? Otherwise I'll bypass it like you suggested just to rule it out.

Nothing short of pulling the motor down and inspecting the water passages could rule out a blockage or a piece of crud floating around causing blockages.

I'm hoping there's slim chance of that I'm also assuming this is rather rare? When I replaced the water pump I inspected it rather thoroughly just to see if there was any damage or worn impeller blades etc. There was nothing. With that being said, what even IS there that could be present in the cooling system to cause such a blockage? Like actually, I don't know haha!

[Willo]

Hi there,

Just a thought, inspect your water pump pulley, if the surface where the belt runs looks polished it may be that the belt is slipping and not turning the pump with enough speed. Have seen this on superchargers where boost was dropping at higher rpm.

Also make sure your drive belt is in good condition and properly tensioned.

Cheers,
Adam.

[Danny]

Consider the coolant re-route.
https://coolant-reroute.com/

[hks_kansei]

Consider the coolant re-route.
https://coolant-reroute.com/

I'd strongly suggest not doing that until after sorting the issue.

If it overheats under normal driving that's a sign something is wrong with it.


A coolant reroute just throws another thing in to diagnose.

Would be like trying to diagnose a sore knee and then just buying new shoes.
might make it feel a bit better, but you've not actually fixed the issue that caused the problem to start with.

[greenMachine]

Started overheating around February this year.

In the absence of anything to the contrary, I am assuming it was ok up to that time.

So what happened in February, or maybe January? Did you do ANYTHING to the car around that time?

[Aiming Faster]

Check that the cooling system pressurises when warmed, a faulty/wrong cap could let all the pressure out into the overflow bottle, and boil a load of coolant into it too.
My son's 323 Astina had a radiator cap without a spring to hold the small 'refill radiator as cooling down' valve closed.
I bought another, it was the same, so I swapped it for a different style cap. CURED!!

[Custardtart]

Check that the cooling system pressurises when warmed, a faulty/wrong cap could let all the pressure out into the overflow bottle, and boil a load of coolant into it too.
My son's 323 Astina had a radiator cap without a spring to hold the small 'refill radiator as cooling down' valve closed.
I bought another, it was the same, so I swapped it for a different style cap. CURED!!

This but also check the reservoir for cracks particularly around the cap, can be hard to spot cold.

[manga_blue]

This is all a bit crazy. Cooling systems are not that hard. An experienced cooling tech should be able to diagnose this in 10 minutes once he gets to look at it. Googling "radiators Ripley" yields a stack of cooling specialists near you. I'd just give up trying to solve it by forum and take it to one of them.

[JBT]

^^^^^^

[Mr Morlock]

I agree with Manga "This is all a bit crazy".- I would take his advice and tell us what the problem was.

[Skifey]

This is all a bit crazy. Cooling systems are not that hard. An experienced cooling tech should be able to diagnose this in 10 minutes once he gets to look at it. Googling "radiators Ripley" yields a stack of cooling specialists near you. I'd just give up trying to solve it by forum and take it to one of them.

I agree with Manga "This is all a bit crazy".- I would take his advice and tell us what the problem was.

Alrighty everyone! Some updates; apologies for going dark - busy over the December period naturally.

I've taken it to Pearls Radiator Works in Ipswich after reading everyone's comments - I figured it was time to bite the bullet. Warwick there was a top bloke; informative and friendly - would recommend him to anyone in the area. He took a look over the car FOC.

I'm going to summarize the conversation below;
- Get rid of the Tridon 'Hi-Flow' thermostat, they're rubbish and open as much as they're faulty
- Put a radiator cowl on it. I mentioned that I originally had one that broke and he said to get another which I've since ordered from Beavis Motorsport.
- He suggested wiring in a manual switch to turn both the A/C and standard radiator fans on. He suggested the airflow on the car might be part of the problem, especially at low speed. Currently only 1 side of my radiator is being cooled at low speed.

This was 2 days ago; I've since bought a Dayco standard thermostat as per his recommendation and put it in last night. It HAS had an affect in that the car overheated noticeably slower but it's still overheating. In fairness this might be due to the fact that the Tridon thermostat I had in there was gutted and drilled out. Warwick explained that it works both ways; if a thermostat restricts flow too much, it's bad. If it doesn't restrict it enough then your water doesn't have a chance to cool down and my flow in my radiator was FAST. 100%. NOTE: I tested the Tridon thermostat in hot water; it wasn't faulty so it's no surprise this didn't fix the problem.

Has anyone heard of people wiring in manual switches for their radiator fans? It doesn't seem a huge task but at the same time I've never read of it being a common necessity with an mx5.

[Red_Bullet]

Fans should only have any effect when stationary or moving slowly, say under 40kmh. Has the ignition timing been verified as correct? What ECU is on this car?

[Custardtart]

So the garage didn’t find the fault? I’m amazed!

I would’ve thought a decent garage would’ve run through a process, eliminating the possibilities as they go.

Wiring in a manual switch is something you’d only do if you had a nugget of a car with spaghetti for wiring.