So I have a bit of an overheating problem with my MK2, if I sit at 70-80mph for a few miles it overheats, slowing down & putting on the heater brings the temp back down - as you can imagine this isn’t a good thing to be doing in the summer! Also not good for the engine to be overheating - wasn’t a problem in the winter months as had the heater on most of the time. There’s no leak of coolant anywhere & I’ve rarely had to top it up.
I’ve previously had the system bled & flushed - issue is still there.
My thoughts on trying to sort this:
Replace fuse for fan (it’s an unlikely cause but cheapest to do).
Replace fan & fan motor - though can’t find them on MX5 parts or on Euro car parts, loathe to put a 2nd hand one in.
Replace radiator - about £80 for an after market one plus a mechanics cost.
Replace thermostat &/or water pump - these should have been changed about a year ago when it was serviced by MX5 Works in Leighton Buzzard (but no confidence in them having done a proper job for various reasons - posted about them in the past) a possibility. This is obviously more costly as I’d need a mechanic to do this & it would mean the timing being done (I assume).
Would need a mechanic in the Glasgow/west of Scotland area - and obviously one with MX5 experience - but tracking one down is proving rather difficult as well.
When you flushed the radiator did you check the flow from top to bottom outlet? These rads can get blocked easily but the flow rate will show significantly reduced with a test.
If the rad is OK and in my opinion that is the most likely culprit you can easily check the operation of the fan. Just wire directly to a battery and expect a vigorous spin. Anything sluggish points at a problem.
Another test is to just start the car and leave it running until the fan cuts in.
MX5’s run reasonably cool so overheating should not happen with a healthy car. My MK1 took 70 miles of high speed motorway driving on a very hot day to expose a rad that looked perfect from the outside but was flowing from the bottom outlet at a mere dribble rather than a medium fast tap.
Sounds a bit odd to me. If you’re traveling at 70 mph I would have thought there should be enough air flow to keep the engine cool without the fan running.
You say your car is a 2000 date so I assume it is pre OBD and has the diagnostic port on the right of the engine bay. If so you should be able to test the cooling fan by connecting a link from the terminal marked TFA and the one marked GND. With the link in place the fan should run. There is more info on this on the web. ( disclaimer, do this at your own risk. )
Good luck.
D
Yes - you would think so but for me apparently not. I guess the rad had been deficient for years before that trip on a hot day undid it. The cooling effect of airflow over a partially blocked radiator is seriously compromised.
The diagnostic port also exists on OBD MK2.5 so as you correctly say easier for the OP to jumper the diagnostic box than fiddle with a battery.
How’s the aircon Combemartian - all working well I hope:-)
Having read through this again I think my money would be on a blocked radiator as Rhino suggests. Remove bottom hose ( having drained the system first of course ) and put a garden hose in the top and make sure there is plenty of flow through the rad.
( Hi rhino, the air con is working now thanks. It was a bit of a battle as I had to strip half of the compressor to clean and reseat the o rings. Got there in the end ?? )
Complicated getting on to of this as I work away from home & only have my car at weekends when I’m home - so this weekend it’s a change of the fan fuse and see how the fan is working (or not).
Not really wanting to do any “work” as such as don’t like leaving my car outside the flat which is a possible if I get started & not finished - having a problem with a neighbour at present & not going to give them something to vandalise - car gets parked up in a secure carpark that costs me £25 / week
Probably not the fan if it’s happening at motorway speeds. My approach would be to drain down system. Reverse flush system with a hose to check there’s no obvious bad blockage. Then remove stat, and if you have a thermometer, check that’s it’s doing its thing when it should, in a pan of water as you heat it up. Replace or not, as necessary. If stat hasn’t sorted it, then try a new rad. Pattern rads available on eBay for around £35. Think that’s what mine cost - my memory’s shocking, and I’m away from my receipts.
Reverse flushing with a hose is a bit of a problem for me - my flat is on the 3rd floor, kitchen & bathroom at back of flat (no access to the back) & I don’t have a hose either which would have to be rather long !