Mx-5 cooling issue.

[Jimmynb]

Today I figured out there is a big problem with my car. I have no flow of coolant to my engine. I cannot tell if it is a problem with my radiator or a problem with my water pump. My car never goes above the centre of the temp gauge. However, after finding out my overflow bottle is consistently empty no matter how often i refilled it, and having separate issues i decided I would (with the help of my father) diagnose the problem. So we ran it and found that there was no flow initially, and then after reaching normal temperature it began to gurgle. So we put the radiator cap back on. When we took the cap off it erupted like a volcano out of the radiator. We found a small amount of rusty liquid on the bottom of the water pump before this experiment from moving it out of my driveway.

TL;DR
I have no flow of coolant to my engine for unknown reasons. Small rusty liquid on bottom side of water pump. Overflow bottle always empty and rusty liquid throughout. Cannot find leak. Radiator erupted upon opening.

My dad and I are thinking we will just buy a replacement water pump of ebay and see if that fixes the problem. If that doesn't we will either flush the radiator or replace the radiator with an aftermarket ebay one. Are there any major issues with ebay or non-genuine replacement parts?

All input is appreciated, Thanks guys.

JimmyNB

[manga_blue]

You have some of the symptoms of a head gasket leak: mysterious loss of coolant, coolant foaming out of the radiator. You get some water sucked into the cylinder on each intake stroke and you get some gas injected back into the coolant on each firing stroke. So water disappears and gets foamy.

I'd first take it to a workshop to get a compression test and/or CO test of the coolant. I'd want to get that out of the way first since anything else is futile if there is a head gasket fault. Replacing the water pump is not very straightforward job in an MX5, it's probably most laborious and least likely solution to your problem.

[ralt]

Hi.
I would replace the thermostat first.

[Mr Morlock]

Manga is always good value- please take his advice in this.

[greenMachine]

First off, check the oil. What colour is it? If it is milky, you have oil and water mixed together. Bad news, not much point looking any further.

If the oil looks ok, you are not off the hook. Fill the radiator and replace cap, start the car, and (after burping all air out of the system) check for leaks. Check all hoses, the radiator itself (especially the top tank) and the heater (difficult, but if it is leaking the carpet will be wet up near the heater core). Fix any leaks (worth trying a new thermostat if the system has been drained), refill radiator, start the car taking care to burp well again, and then replace radiator cap. There is a slim possibility that your head gasket is not blown, and finding and fixing some leaks will stop it consuming water. BE CAREFUL when removing radiator cap from hot radiator, if it is pressurised the merely hot water will boil when pressure is released.

It sounds like a blown head gasket to me, but is worth trying a few diagnostics if it results in a fix that does not involve lifting the head. You should also think about replacing hoses (do all, or don't bother doing any) and even the radiator if you think these are the originals. The radiator is a known failure point, the top tank starts to fade and develop crazing - failure mode can be leaking, or it can just blow out large chunks of the tank leading to virtually instantaneous total water loss.

Good luck

[93_Clubman]

buy a replacement water pump

Just something to consider - if you're replacing water pump then also replace the timing belt. Which begs the question has your timing belt been replaced, & when was it replaced, as water pumps are recommended to be replaced at the same time as the timing belt, so it may have already been done in which case replacing it again may not solve the problem.