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Author: Subject: MX5 engine disaster - help needed.
richardh

posted on 1/9/21 at 09:43 AM Reply With Quote
MX5 engine disaster - help needed.

Hi all,
I've not posted on here much, been too busy on the old FB forums etc.
This is still the best place to get valid responses though so I thought I'd try asking here.\

The problem:
Somehow, I think the new alternator belt (been on for about 200 miles) decided to throw itself off, leading to a failure to turn the water pump and then an overheat.
I now can't get the spark plug leads off the engine as they seem to be melted to the plugs.

What I've checked so far:
Alternator is also new and I think it aligns up properly. (Been out driving several times and not had an issue) and it's fully spins nice and freely.
Water pump pulley spins nice and freely also.
I can still crank the engine over by hand with a socket and it seems nice and free and I can hear compression out of the intake manifold.
I've removed the (was new and saucepan tested OEM thermostat) and it's a gunner.
Have used a hose to make sure that water flows through the engine and out the bottom hose ok and it does.
Doesn't appear to be any coolant in the oil so far. nothing in the oil cap nor dipstick.
Coolant looked ok, maybe a little rusty but not too worrying.

What to do next:
I need to get the plugs out and then this is where the advice I get varies massively.
1) put new plugs and leads in and start it up and see what smoke colour there is
2) drop oil, check colour and then do step 1
3) drop oil, remove rocker cover, check all looks ok as turn over engine by hand and then go to step 1
4) remove head and check it's ok with and not needing skimmed, new gaskets and then back to step 1
5) as per step 4 but also do valve stem seals and piston rings then step 1
6) drop a used replacement engine in and be happy (hope it's all good as won't have any idea about it's condition)
7) give it to somewhere that'll charge me a fortune and not really know what they are doing (spoken to several alleged experts on engines and got the above options from them.

My issue:
I assembled the car ok, but I'm not familiar with stripping down 4 pot engines at all. I'm told this work is all easy stuff but I'm lacking the confidence to do it without guidance or help to make sure I do it right.

The ask:
Is there anyone in Kent (I'm Tenterden) that's good with engines who would be ahoy to help us out on this?
We can talk remuneration for time etc for sure. Learning how to fix this would be far more useful for future and I've probably already got most of the bits needed but can order whatever would be needed.

I've looked through YouTube loads and googled and got the Haynes but haven't found one or a combination that seems easy to follow.

Yours in all hopefulness.
Rich





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Mr Whippy

posted on 1/9/21 at 12:23 PM Reply With Quote
Why would you take the head off? Just do a compression check and then one with the coolant system. Unless the oil or coolant is contaminated I'd just go on the assumption that the head gaskets are fine. You could even just chuck some head gasket sealant in the coolant to be sure. You know why it overheated and I'm assuming you've just changed the belt so just do a couple of quick checks, fill it back up and drive the car. Don't make a mountain out a mole hill.
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gremlin1234

posted on 1/9/21 at 12:27 PM Reply With Quote
the series shows overhauling an mx5, there are a few free episodes, but 20 for them all.

https://www.howacarworks.com/video-course/watch/bonus-dismantling-the-engine

https://www.howacarworks.com/video-course/watch/engine-block

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adithorp

posted on 1/9/21 at 12:29 PM Reply With Quote
Define "overheat"
Did it...
1) just run hot on the gauge and you stopped?
2) Boil up and steam from the pressure cap and you stopped?
3) You didn't not know/notice it was overheating and continue until the engine packed up.

One and two, refill coolant and fit new belt and see what happens.

[Edited on 1/9/21 by adithorp]





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richardh

posted on 1/9/21 at 01:11 PM Reply With Quote
Thanks.

I'll look at those links.

It went to top of gauge then went down a little, back up and we stopped. We were on the motorway hard shoulder so did this 3 times.
It didn't blow the rad cap nor the oil cap. We had some steam from the overflow on the expansion tank on last stop.
Engine still runs as I drove it off the recovery truck up drive and into garage.

Compression checks good idea. just got to get these damn leads and plugs out.

Cheers for constructive comments





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jelly head

posted on 1/9/21 at 02:14 PM Reply With Quote
Agreed with whippy, why pull the engine apart unless you really have to.
I'm not familier with the plug set up on mx5s - are the plugs down in wells in the centre of the head?
If it was me i'd try and rag the leads off, change the plugs and run it and see what happens then worry about the rest if / when...

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adithorp

posted on 1/9/21 at 03:26 PM Reply With Quote
If that's all, I wouldn't panic. It's certainly not a "disaster". Lots of engines have that sort of overheat and probably less than 1 in 10 it's done any long term damage.

Put a belt on (check the pulleys are aligned ok and not the reason you lost the first one), top up coolant and see how it goes. Certainly don't start stripping anything down.

As for the plug leads. In 40yrs in the trade I've yet to see a melted plug lead end. I've seen engines that have been so hot every plastic bit on the engine has melted but not the HT ends. More likely there just stuck to the plugs plus a bit of vacuum to overcome. Sometimes that can be a pretty strong bond and might tear the rubber occationally. Twisting can work better than pulling. If it takes a lot of force you might be best of replacing anyway as the crimping can suffer.





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Mr Whippy

posted on 1/9/21 at 03:27 PM Reply With Quote
I've had a couple of overheats, one due to the alternator falling off, snapping the belt, smashing the fan and puncturing the rad. The other on a Bluebird due to burst hose, both were proper steam engine coolant all over the place jobs. Neither resulted in any engine damage and were on the road the next day. So don't be too concerned. Over heating use to be very very common occurrence in the summer.

As for the melted plug leads, well the leads should be silicone so can't melt, perhaps the shrouds are plastic but brute force will get them off, maybe with some WD40 and a screw driver... Just budget for some new leads and plugs.

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russbost

posted on 2/9/21 at 07:56 AM Reply With Quote
Order new leads & plugs, get the old ones off anyway you can, break the plug tops off if necessary, just make sure any ceramic bits don't finish up dropping into a bore.

Once the new leads & plugs are fitted, just do a few local runs with it, see if the cooling system is pressurising excessively (most likely sign of gasket failure), make sure fan is coming on & off as it should & once cooled check coolant to see if any has disappeared.

Hope you've got away with it





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nick205

posted on 2/9/21 at 03:27 PM Reply With Quote
Don't recall having a tin top overheat, but my Pinto engined MK Indy did once. Dumped it's coolant 3 miles from home, but a steady drive got me home and no damage done.
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richardh

posted on 3/9/21 at 08:30 AM Reply With Quote
Thanks all, hopefully I'll know more after the weekend when I can go and get the bits and try it.





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Mr Whippy

posted on 3/9/21 at 09:13 AM Reply With Quote
I'd stick the hoover nozzle down the spark plug bores before taking the plugs out just in case there's debris in there
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macc man

posted on 3/9/21 at 07:45 PM Reply With Quote
I overheated my Vectra engine when the coolant pump disintegrated. Temp gauge went off the scale and loads of steam. I thought it would have caused lots of damage but after fitting a new pump and fresh coolant all was fine. It ran for many years after with no problems.
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richardh

posted on 6/9/21 at 09:03 AM Reply With Quote
Thanks for the replies.
Update:
Old plugs and leads removed with a lot of care and a hoover nozzle modification.
Oil changed, old was almost black.
Turned car over by hand and still seems ok.
New alternator belt fitted and checked for over-tension.
New plug and leads on.
Radiator checked, fans swapped to internal and to sucking air.
Raised front end and filled with water to start with.
Ran up to temperature and both the top and bottom hose are now hot.
Left for about 10 mins and the fans kicked in ok.
Oddly the gauge didn't go above half way at this point whereas before the fans would kick in if the gauge got to about 3/4 way.

I've removed the thermostat and don't plan to run one.
I don't like the coolant expansion where it is and may change to one where it's lower than the rad cap and is a top fill from overflow from radiator. Might stop the air being sucked back in then.

The other think I'll do is find an ignition fed supply and take a fused connection from that and run the fans as the engine is on and not rely purely on the temperature sensor at the back of the engine block.

Oh and add a coolant re-route kit too soon.





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gremlin1234

posted on 6/9/21 at 10:43 AM Reply With Quote
quote:
Originally posted by richardh
The other think I'll do is find an ignition fed supply and take a fused connection from that and run the fans as the engine is on and not rely purely on the temperature sensor at the back of the engine block.

I think I would put a relay in for that

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sebastiaan

posted on 6/9/21 at 11:14 AM Reply With Quote
Looks like you got away with it.

But also:
quote:
Originally posted by richardh
I've removed the thermostat and don't plan to run one.
[....]
The other think I'll do is find an ignition fed supply and take a fused connection from that and run the fans as the engine is on and not rely purely on the temperature sensor at the back of the engine block.




I think you are over-doing it. This was caused by the engine throwing a belt, and no stat + fans always on = recipe for over-cooling and all the related issues. I would advise you to put the thermostat back in and rely on the sensor that does the job for thousands of MX5's. If in doubt, fit a new OEM one and incorporate a big temp warning light in the coolant re-route to ease your senses.

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adithorp

posted on 6/9/21 at 05:37 PM Reply With Quote
Put the stat back. Running without isn't a good idea. It will cause slow warmer up, probably overcooling and can adversely effect flow. It won't stop it overheating if what happened again.
Running the fan constantly again won't help with what went wrong. At speed I found having the fan running kforgot to turn off the override) actually reduced cooling on my car. If your worried, fit an override switch which can be handy in extream conditions.

Stop overthinking. If you want something to concentrate on check your belt alignment.





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indykid

posted on 6/9/21 at 08:59 PM Reply With Quote
I drove my mk1 1.8 MX5 back from huddersfield (9 miles) with very very little coolant after the bottom of the rad split at work and dropped all the coolant into the gravel car park through the day.

The gauge didn't show particularly hot because it was in fresh air, but it started stuttering about 300yards from home. I coasted it down the hill, dumped it on the drive and let it cool down - it wasn't steaming anymore, it was red hot and everything was pinging. Filled the coolant back up and it ran on for another 25k miles to over 200k when the engine was still running like an alarmed hominid but the bodywork has given up.

They're pretty indestructible engines.

Also put the thermostat back in.





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coyoteboy

posted on 10/9/21 at 03:26 PM Reply With Quote
quote:
Originally posted by richardh
Hi all,
I've not posted on here much, been too busy on the old FB forums etc.
This is still the best place to get valid responses though so I thought I'd try asking here.



Facebook is killing forums. Here won't be about soon at this rate.


quote:

The problem:
Somehow, I think the new alternator belt (been on for about 200 miles) decided to throw itself off, leading to a failure to turn the water pump and then an overheat.
I now can't get the spark plug leads off the engine as they seem to be melted to the plugs.




What tells you you need to strip the head off? Down on compression?
Why would an overheat melt the plug leads to the plugs (the metal, or the insulation?) Pull harder?
If you think the metal has melted, the whole damn engine is toast and you might as well just bolt it out and bolt a new one in, surely?





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richardh

posted on 13/9/21 at 12:52 PM Reply With Quote
quote:
Originally posted by coyoteboy
quote:
Originally posted by richardh
Hi all,
I've not posted on here much, been too busy on the old FB forums etc.
This is still the best place to get valid responses though so I thought I'd try asking here.



Facebook is killing forums. Here won't be about soon at this rate.


quote:

The problem:
Somehow, I think the new alternator belt (been on for about 200 miles) decided to throw itself off, leading to a failure to turn the water pump and then an overheat.
I now can't get the spark plug leads off the engine as they seem to be melted to the plugs.




What tells you you need to strip the head off? Down on compression?
Why would an overheat melt the plug leads to the plugs (the metal, or the insulation?) Pull harder?
If you think the metal has melted, the whole damn engine is toast and you might as well just bolt it out and bolt a new one in, surely?


The leads were so melted onto the plugs and into the engine I had to break, cut, drill them out and break the spark plug tops just to get the socket on them.
With that much overheat and pressure build up, something would surely need to give out, the gasket being the most obvious weak point first.

Updated - put it back together and it looks like I'll be needing to do the head gasket at the least anyway.





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Mr Whippy

posted on 13/9/21 at 02:47 PM Reply With Quote
oh well a good time to change the belt and pulleys anyway. The Haynes manual on the mx-5 covers the head sufficiently for you doing it yourself.
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