My OH just boiled her MX5

[Johnnytheboy]

My OH jusr arrived home, as she came down the road there was steam billowing out of the wheelarches. Apparently it had been doing this for the last ten minutes but she "just wanted to get it home".

Oddly, she says it was showing normal water temperature.

There's a a few drips coming from underneath the rear of the engine bay and no water in the radiator header tank. No obvious escape point of the water/steam in the engine bay when she first got home & I opened the bonnet.

As the garage we use is near where we both work 30 miles away, I'm inclined to top the coolant up and get her to attempt to drive it in tmw and if it steams again, get towed to garage, as whatever happens it has got to go there.

What do we think this is then?

N.B. this is a mk1 with a 6 figure mileage, so if it's major it'll have killed the car

[Johnnytheboy]

Water is pouring out of the back of the engine bay somewhere as fast as I pour it in the radiator.

Think we'll get it towed.

Or should I tell her it'll be fine, then emigrate?

[J-Tuner]

You might be lucky and a pair of heater matrix hoses will fix that! Circa 25 notes. That's if the head gasket hasn't been trashed from overheating !

[Johnnytheboy]

Just to be on the safe side I've started looking at mk3s in the classified.

[longshot]

Did it finish the water and start on the oil?

[Johnnytheboy]

Don't know... the oil cap looked nice & clean - as it was pretty hot testing the oil seemed pointless.

[Eighteeteewhy]

Is the alternator/water pump belt still on?

[Johnnytheboy]

Yep - and yes, it has all its oil still.

[MX-5 Lazza]

Sounds like one of the heater matrix hoses to me. A bit awkward but otherwise cheap and easy enough to DIY. Probably means the CAS o-ring is leaking oil too - get that sorted at the same time

[longshot]

Johnnytheboy said:

Yep - and yes, it has all its oil still.

Ace.

[NiceCupOfTea]

MX-5 Lazza said:

Sounds like one of the heater matrix hoses to me. A bit awkward but otherwise cheap and easy enough to DIY. Probably means the CAS o-ring is leaking oil too - get that sorted at the same time

This and this. Textbook failure on the Mk.1, CAS o-ring starts leaking onto heater matrix hose, hose fails. I had it on mine.

Temp gauges are funny things - the MX-5 one is damped and stays in the centre for all normal temp ranges (fit a proper temp gauge and you will see it vary by 10 degrees in traffic on a hot day as the fan cuts in and out - MX-5 gauge doesn't budge). Do bear in mind that if there is no water on the sender then the sender won't show it overheating!

Best thing you can do is replace the hoses and run it with water in the system for a few days. If it's not been cooked, flush and fill with coolant and get that o-ring changed.

[Johnnytheboy]

Ok, it's getting towed to the trusty Colehill Garage in Wimborne in the next few days.

They'll sort it if anyone can.

[cwinterb]

NiceCupOfTea said:

MX-5 Lazza said:

Sounds like one of the heater matrix hoses to me. A bit awkward but otherwise cheap and easy enough to DIY. Probably means the CAS o-ring is leaking oil too - get that sorted at the same time

This and this. Textbook failure on the Mk.1, CAS o-ring starts leaking onto heater matrix hose, hose fails. I had it on mine.

Temp gauges are funny things - the MX-5 one is damped and stays in the centre for all normal temp ranges (fit a proper temp gauge and you will see it vary by 10 degrees in traffic on a hot day as the fan cuts in and out - MX-5 gauge doesn't budge). Do bear in mind that if there is no water on the sender then the sender won't show it overheating!

Best thing you can do is replace the hoses and run it with water in the system for a few days. If it's not been cooked, flush and fill with coolant and get that o-ring changed.

Similar issue in my mk1 soon after I got it. Arrived home from a run and as soon as I stopped could smell hot coolant then noticed a few wisps of steam from under the bonnet. I'd had the CAS o-ring replaced as a precaution and just as well as it had obviously been leaking onto one of the heater hoses which developed a pin hole leak. Had I not stopped I am sure it would have developed into a big hole and cooked it. I swapped all the hoses for a silicone set from MX5 parts. The hoses are all reasonably accessible, if fiddly, apart from the one buried under the inlet manifold. I had to remove the throttle body which allowed just enough access to change it.

[Johnnytheboy]

Apparently all fixed, being collected tomorrow.

It would seem the only way to kill an MX-5 engine is fire, or driving a wooden stake through the cylinder block.

ETA and it was exactly what PH said it was, and yes I've had the CAS o-ring replaced.

Thanks all.

[scrwright]

First one I bought had been overheated so bad the plug leads had turned to liquid and then set solid around the plugs. One water pump later & hours chipping away at the melted plastic around the plugs to get new leads on it ran fine.

[VladD]

Just to piggy back on this thread, I had a hose go a few weeks back and was thinking of replacing all of the hoses with a set from MX5 parts. From this thread I've learnt that I should replace the CAS O-ring too. Is there anything else worth doing at the same time? One thing I was thinking of was a coolant system flush.

[Johnnytheboy]

Total garage bill to fix this coolant pipe & CAS O-ring, lube up a jammed passenger window mechanism and supply me a new dipstick (old one's top bit had perished) - £160.00.

Colehill Garage

[NiceCupOfTea]

VladD said:

Just to piggy back on this thread, I had a hose go a few weeks back and was thinking of replacing all of the hoses with a set from MX5 parts. From this thread I've learnt that I should replace the CAS O-ring too. Is there anything else worth doing at the same time? One thing I was thinking of was a coolant system flush.

You could do - how old is the radiator? On mine the radiator was flowing and not leaking, but car was still getting too hot after flushing/backflushing several times and was only sorted by a new radiator.

IMHO the cooling system on MX-5s can be a weak point if neglected.

[VladD]

NiceCupOfTea said:

VladD said:

Just to piggy back on this thread, I had a hose go a few weeks back and was thinking of replacing all of the hoses with a set from MX5 parts. From this thread I've learnt that I should replace the CAS O-ring too. Is there anything else worth doing at the same time? One thing I was thinking of was a coolant system flush.

You could do - how old is the radiator? On mine the radiator was flowing and not leaking, but car was still getting too hot after flushing/backflushing several times and was only sorted by a new radiator.

IMHO the cooling system on MX-5s can be a weak point if neglected.

Not sure how old the radiator is. I'm not having any overheating problems, I just thought it might be worth doing since I would have to drain the system to fit the new pipes anyway.

[NiceCupOfTea]

Might as well - I used Holts stuff. Follow the instructions, flush it through, and use decent coolant