Hi, I’ve got a 1997/98 NA Eunos Roadster and have recently been experiencing some overheating issues. I know the radiator is most likely the cause, as it’s still the original one that came with the car and the top has gone brown. I was just wondering, where should the temperature gauge needle typically sit at motorway speeds (around 60–80 mph with the odd hill) with a new OEM radiator?
Picture shows roughly where the temperature needle tends to fluctuate up to while driving on the motorway — it usually cools back down to the middle when going downhill under low load.
The gauge should be in the middle. First, check the coolent level, then Take the thermostat out and test it by putting it in a bowl of boiling water. see if the valve moves. While the thermostat is out, connect the thermostat housing back together and take a test drive. If it still overheats, you probably need a new water pump.
The thermostat is new so it’s not that. The heater in the car works consistently so if it was the water pump I would have thought the heater output would be inconsistent or not working at all.
It’s something I’ve always done, as recently as two years ago on a friend’s Focus. (that modern replacement was OK.)
This was after having been bitten in the bad old days of student motoring by the notorious Waxstat thermostats widely used on UK cars of the 1960s and 70s; two new ones in a row were faulty out of their sealed packs for my first Mini.
I sent it off to a classic car specialist to have a new OEM thermostat fitted. Since it’s a 1.8, the thermostat is tucked away at the back of the engine, which makes it a bit of a pain to get to. They tested the system and it was holding the temperature fine. They do think the car is showing the typical symptoms of an old, worn-out radiator.
I had a similar issue. In my case it was the radiator needed replacing as multiple fins were flattened by detritus and the odd bird hitting the rad. Subsequently replaced the rad and have fitted a radiator grille.
I’ve booked the car in however, I’m supplying the parts. Can anyone confirm if this OEM Mazda radiator will work with my 1.8 Eunos with A/C. Also if I was to get the timing belt done, should I buy just the belt or the whole kit.
If you are doing the timing belt, get a kit and do the tensioners and the spring at the same time. To be frank if the cost of the water pump is not too much for you, i would do that at the same time as it is just easier with it all to bits anyways.
With the new rad, flush the block. Corrosion builds up and silts up the rad but also the galleys in the block.
After 35 years dealing with motorway breakdowns I would strongly suggest that if the car is running hot without losing coolant it’s almost certain a lack of circulation caused by a blocked radiator (furred up) inside. I would expect the temperature to drop back once the load is taken off the engine. I don’t think you will lose anything by fitting a new radiator.
If it has got up to that temperature that’s not good; overheating like that can lead to a blown head gasket. As others here have suggested it could be a partially/blocked radiator; although I found from experience that some of the smaller bore rubber hoses can cause restricted flow and increased temperature as a result; any detritus in the coolant can easily block these and if the hose inside is degraded this can happen.
The temps skyrocket very quickly and unexpectedly sometimes (other times it creeps up normally like you’d expect), and there’s not much that can be done apart from putting the heater in full and turning on the A/C to get the second fan running. New radiators on its way along with a water pump as I’m doing the timing belt as well. Luckily the oil looks normal so no signs of a blown headgasket yet.
I had a mk1 with this very problem, a new thermostat (the front of the engine), did not solve it, but that is because it was faulty, I bought off Ebay and for something this serious, please spend the extra and buy from a quality seller.
I got lucky, I drove 1 junction on the Mway, parked up, drove back after it cooled at much lower speed.
If you do not really use the AC, I would remove and swap to a new larger Alloy rad, and have both fans running cooling. I have had this set up on my old MK1 (rest in peace) and my mk2.5 Sport, it makes a good difference, especially on track on spirted driving
I would swap the Rad, and hoses and see what’s what from there
Hi all, just thought I would post an update. Replaced the radiator and waterpump (came in the cam belt kit) and that seems to have solved it! The needle now sits at just under halfway on the gauge even doing 70 up a hill on the motorway. I believe the random spikes/rapid temp gauge change was due to the temp sensor or wiring getting heat soaked when it was running relatively hot which means it was giving a false reading (although that’s just a theory).
