Mk1- Coolant loss / overheating troubles...

Mk1- Coolant loss / overheating troubles...

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Discussion

vrsmxtb

Original Poster:

2,002 posts

155 months

Monday 1st August 2011
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Not fully with the stat out, but I've changed the water twice and it is still a little brown each time, although the rad itself is flushing crystal clear. Do you need to take the big plastic airbox off to get the stat out? Looks a bit tight to access the bolts?

NiceCupOfTea

25,280 posts

250 months

Monday 1st August 2011
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The plastic pipe across the front from airbox to manifold? Yes, but it's 2 minutes work, just a couple of jubilee clips.

IIRC yours is a 1.8 like mine, when you have the stat cover off, make sure you clean out the little pipe that goes off to the side as that can get blocked. The 1.6 is different.

vrsmxtb

Original Poster:

2,002 posts

155 months

Monday 1st August 2011
quotequote all
I'm pretty sure I have a blown headgasket, as it is still pumping coolant out the tank and bubbling once the engine is shut down. Probably a water/oil channel rather than an exhaust gas seal hence the sniffer test being negative.

bks! mad

NiceCupOfTea

25,280 posts

250 months

Monday 1st August 2011
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Any mayo under the cap? Compression test?

vrsmxtb

Original Poster:

2,002 posts

155 months

Tuesday 2nd August 2011
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No mayo under cap. I haven't had a compression test done yet, but I'm starting to think the colour of the coolant may have been oil related, as some of the sediment that as flushed out felt greasy once Id emptied the container I collected it into. Also I have noticed quite a few water droplets/vapour from the exhaust when started from cold.
It's about the only thing left to change! If I spend another £500 on it and it still does it I am selling up!!

NiceCupOfTea

25,280 posts

250 months

Tuesday 2nd August 2011
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Fair enough - although droplets from a catted car are normal.

I'd get a compression test, good luck!

vrsmxtb

Original Poster:

2,002 posts

155 months

Wednesday 3rd August 2011
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Thanks for your input nicecupoftea smile

Will report back once I have the compression test results and/or can afford the HG change. I'd love to be brave and do it myself but just don't have the tools / knowledge or working space.

If the car is not overheating and coolant is kept topped up it should be Ok to keep driving for a while, if maybe a bit more Miss Daisy-style!?

  • Sigh* the idea of the cheap second car that only needed a new set of boots and a geo set-up is long gone.

NiceCupOfTea

25,280 posts

250 months

Wednesday 3rd August 2011
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I reckon you'd be OK, but watch the temp gauge like a hawk as it's not linear, and once it starts rising it's overheating!

If the worst comes to the worst, new engines are cheap!

I must admit when I was having the same problems, and before I'd swapped out the rad, I had been considering the head gasket - I was trying to build up the guts to give it a go myself. It's a non interference engine, so in theory if you get the timing wrong it just won't run rather than causing damage!

IMHO the reputation for bulletproof mechanicals doesn't do the '5 any favours - people neglect stuff, especially the cooling system, which can have disastrous results!

TehMonkey

387 posts

186 months

Thursday 4th August 2011
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When the engines getting hot, does the heater blow warm/hot air?

vrsmxtb

Original Poster:

2,002 posts

155 months

Thursday 4th August 2011
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TehMonkey said:
When the engines getting hot, does the heater blow warm/hot air?
Yeah heater works perfectly.

vrsmxtb

Original Poster:

2,002 posts

155 months

Saturday 6th August 2011
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Well this is becoming a real saga now. Had yet another opinion from a very good mechanic who has touch wood pinpointed the problem to some kind of intermittent electrical fault with the coolant temp sensor which wasn't controlling the radiator fan correctly causing overheating and big build-up of pressure. I had seen the rad fan working but now I think of it I'd never heard it keep spinning after parking up and turning the ignition off.

There's still a mystery about the coolant gauge as that still showed a reading when he unplugged the sender socket on the back of the engine bay, and very rarely moved to show overheating. Apparently there's two electrical sockets but one seems to have a blank or broken plug in it.

At the moment I have a small removable bridge on the fan relay to keep the fan on permanently when driving, plus I'm running without the 'stat at the moment. Hopefully this should create a nice cool engine and solve the big pressure build-up causing the expansion tank overfilling, if so touch wood its a new £50 temp sensor and temp guage sender and job done!

Definitely no head gasket failure which is good news.

Paul Dishman

4,676 posts

236 months

Friday 12th August 2011
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Interesting thread.
We've had a similar problem with my wife's 10AE since shes owned it. We did the easy things last year- flush the system, new rad cap which appeared to help but didn't really solve the overheating in slow traffic or, for example, when putting the engine underload by climbing a hill.

In the end it went to the local Mazda dealer who have sorted it by installing a new radiator. The old radiator looked fine, but you can't tell by looking at it. The Mazda radiator was £128+Vat so no more expensive than buying from MX5 parts and the Mazda tech took the car home with him to drive it in heavy traffic to check that it wasn't still overheating. Sue drove it back across Exeter in really heavy traffic yesterday so problem (fingers crossed) solved

vrsmxtb

Original Poster:

2,002 posts

155 months

Friday 12th August 2011
quotequote all
Paul Dishman said:
Interesting thread.
We've had a similar problem with my wife's 10AE since shes owned it. We did the easy things last year- flush the system, new rad cap which appeared to help but didn't really solve the overheating in slow traffic or, for example, when putting the engine underload by climbing a hill.

In the end it went to the local Mazda dealer who have sorted it by installing a new radiator. The old radiator looked fine, but you can't tell by looking at it. The Mazda radiator was £128+Vat so no more expensive than buying from MX5 parts and the Mazda tech took the car home with him to drive it in heavy traffic to check that it wasn't still overheating. Sue drove it back across Exeter in really heavy traffic yesterday so problem (fingers crossed) solved
I've done a lot of trawling the internet on this and yes a new rad will fix 90% of MX5 overheating issues it seems. They are very sensitive to clogging up, which restricts the water flow. I've had all the cooling system replace excet for a full hose change and nothing worked, but it is really looking like the temp sensor was my fault all along! Still nice to have a new rad, pump etc for peace of mind I suppose. If your wife's still does it, check that the fan is kicking in correctly.

vrsmxtb

Original Poster:

2,002 posts

155 months

Thursday 1st September 2011
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Thought I'd update this - today I changed the ECT sensor (remove the coilpack for access) and it seems to be behaving itself - no overheating, overflowing, bubbling etc etc. It seems it really was as simple as a knackered sensor not triggering the cooling fan. Touch wood....

NiceCupOfTea

25,280 posts

250 months

Thursday 1st September 2011
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Fingers crossed!

vrsmxtb

Original Poster:

2,002 posts

155 months

Thursday 8th September 2011
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Bugger. After a drive on a warm day, including idling in traffic for 15-20mins I had still lost all coolant from the expansion tank when checking next day at cold. But at least the fan now comes on!

I think I'm getting a bit of white smoke out the exhaust and high dipstick oil level when checking from cold which makes me suspect head gasket again. Tempted to just bung k-seal in and see if it improves things and get gasket done when I can afford to

Seriously getting annoyed with this car now furious

NiceCupOfTea

25,280 posts

250 months

Thursday 8th September 2011
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Bloody hell!

Are you sure the coolant came from the overflow pipe? Couldn't be a crack in the reservoir?

Do a sniff test - if you are anywhere near SE London I have a kit of ebay that checks the coolant for exhaust gases present - can be an indicator of HG woes. Have you had a compression test done?

vrsmxtb

Original Poster:

2,002 posts

155 months

Friday 9th September 2011
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Hey Nicecupoftea! Welcome back laugh The reservoir tank is fine, it doesn't leak. It's still either losing water within the system so sucking back all the overflow as it cools or expelling water out the overflow again, but not sure which it is now! The weird thing is it varies so much, some drives it will lose water, other times it is absolutely fine. I was running it without the 'stat for a while and it seemed to behave itself like that. But the stat definitely opens as the top rad hose gets very hot, so I don't think that is a problem.

Also I have had two sniff tests done which were negative but I'm worried it could be a gasket leak between a water/oil channel, rather than at the cylinder.

Aside from changing every single water hose to eliminate pinhole leaks, the only other thing I haven't done now is the head gasket frown

NiceCupOfTea

25,280 posts

250 months

Friday 9th September 2011
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One other thing - when you had the thermostat out, did you clean the little pipe that goes out of the housing to one side? Could be silted up...

vrsmxtb

Original Poster:

2,002 posts

155 months

Saturday 10th September 2011
quotequote all
NiceCupOfTea said:
One other thing - when you had the thermostat out, did you clean the little pipe that goes out of the housing to one side? Could be silted up...
No, and I've come across this mentioned before so am going to clean this when I remove the thermostat and run for a day.