Good evening folks, MX5 newbie here so please bear with me!
I recently picked up a '99 1.6 NB for next to nothing, for one to try and understand what all the fuss is about, and two to work on as a little gateway drug in to the world of automotive DIY/self-servicing.
Problem #1 is that it’s overheating. It’ll quite happily keep the needle slightly to the left of centre sat on the drive idling (after reflushing the coolant I let it sit for ~60 minutes with the heaters on full whack and it was happy enough), however get it out on the road and it quickly hits boiling point (from warm will drive for ~10 mins before the needle starts creeping its way to the right). Luckily I’m not seeing any white smoke out of the exhaust, the oil looks clean and there’s no muck on the underside of the filler cap so I’m praying that the head gasket is still in decent shape. It sips coolant and I’ve eyeballed each hose - no visible leaks. Are there any other steps I can take myself to try and figure out what’s up before I start swapping out components and going by process of elimination?
Problem #2 is that I’m getting serious juddering (in every gear and in neutral) at anything below 2,500rpm. Let the car coast down to 1200rpm in gear, then foot flat to the floor and it’s shakes and jerks like a mad man. As soon as it hits that 2.2-2.5k mark though it clears up I and get what feels like normal power output up to the limiter. I haven’t found much of anything online that covers what I’m experiencing here so any suggestions would be greatly appreciated.
Thank you! Not off to the best of starts but even in the 5 minutes I had before I noticed we were overheating I was having the time of my life in it!
Have two litres of coolant available at the car not, I will get it if I need it.
With the radiator cold and a very insulative cloth to stop possible burns.
Take the radiator cap off and if you want take the expansion tank cap as well.
Now start the engine and just stand there for about 15 minutes and watch the coolant level in the radiator it is possible there is an air lock in the system and over that time the air may well come out and it can take up to 2 litres of coolant. I assume when you ran the car for an hour you did not do that if you did then go on to the next idea.
Notice I mention coolant not water. If you use water to get the issue investigated you then have to redo the antifreeze when things are sorted but you know that.
I have told many people to do this with a similar problem and they phone me back after 5 minutes to say that is not the issue. It will take longer than that for that to get the air out.
Next least expensive is to purchase a Mazda genuine thermostat to replace the existing one, then go through the same instructions as before after the first fill of coolant.
After time the radiators get blocked up not them all but a fair few, therefore that is the next change more expensive than a thermostat.
Diagnostics either go to Autolink to by one of these.
Yesterday when I let the car run with the heaters on I had the front of the car up on axle stands (I read that it helps force any airlocks out the system) and I did run it with the radiator & expansion tank caps off. It went through close to everything in the expansion tank and then seemed to stop. And yes I am just using plain old tap water at the moment otherwise I’d be going through pricey coolant like there’s no tomorrow.
I’ve just ordered a radiator, thermostat and a couple of replacement hoses as a next step. One thing to note is after the fan kicks in (I’m presuming the “click” I hear when the engine gets up to temp is the thermostat) I’m not seeing any obvious movement in the top of the radiator. From what I’ve read it sounds like a should be seeing a decent stream of liquid passing through - I’m not seeing that (although it must be said that both hoses in/out of the rad are hot).
I’ll wait for the rad & thermostat to turn up and go from there. Thanks again for the response.
Good news! New rad + thermostat installed and the car is now running at a normal temperature.
On the Monday night (before any of the parts arrived) I decided to rip the thermostat out and go for a quick drive without one altogether (component by component elimination). And my hopes were given a boost when this absolute mess of a thing is what came out;
The rod that slides through the middle as the spring contracts had actually bent at the top - effectively rendering the thing useless.
However, after a ~15 minute drive that pesky temp gauge creeped past the 12 o’clock mark and things started overheating again. Not as bad as before but things still weren’t right.
The next day my new radiator, radiator cap, hoses & thermostat turned up.
New thermostat vs old;
Shiny new rad w/ yellow hoses;
Swapped out old parts for new, took me roughly 90 mins (was my first time doing anything like this and I was running out of light so I was crawling it). Judging by just how brittle the plastic on the old radiator was as well as how crusty and dry the old hoses were it wouldn’t surprise me if the whole setup’s been untouched since it came off the factory line in 1999.
Managed to get everything in and up & running just before I ran out of light completely;
Let the car sit idling for ~30 minutes to allow any air out then went for a drive. Gradually pushed the car more & more until I was thrashing the thing on the redline as much as possible, and the temperature gauge never creeped past the 11:30 mark!
Popped the bonnet after I got home and everything was looking very good indeed.
Absolutely chuffed - now on problem number two! Car is still juddering & jerking at <2.5-3k RPM. New HT leads and plugs on the way as a first step. Any suggestions/experience with low RPM judder would be greatly appreciated!
