mx5cartalk.com

Hi guys, I've just recently purchased my very own mx5, and thankfully Ive found this site. Ive been reading through for a while, and I think its time to start posting.

So my apologies first if Ive violated any terms and conditions, I think i'm posting in the right place....

Well here goes, the problem..

After purchasing the car, I had the head reconditioned by a mechanic I wish I had never looked up. After getting the car back to me, he seems to have no idea why the oil and temp gauges wont work. He thinks he has narrowed it down to a plug directly behind the head, between the rocker cover and the firewall. There is one plug hanging off the loom, and one plug bolted directly onto the back of the head. The problem is that the loom plug has a triangular shape, whereas the bolted plug is rectangular. Ive had enough trouble as it is and I really want to get things fixed, any help is appreciated!!

Thanks guys,
mx51982

Where are you located?

Have you tried the forum sponsors for advice?

Hi mx51982, welcome to the obsession.
You would think if your mechanic recond the head he would put everything back the way he found it.

Anyway the link below may help you to find what your after

viewtopic.php?f=76&t=41364

Cheers
Dale

Hi mx51982, welcome to the obsession

Couple of things are making it hard to help you.
One is your location as Rawsouth has said - don't just put it in a post, put it in your profile so we know roughly what part of Australia you live in.
Another is the type of MX5, a hint like the year, better still the model would assist us armchair mechanics.

Gosh I can't believe I forgot to add the car details.

It is an NB series 1, hope that clears it up for you guys.

I am located in Melbourne, i wasn't aware that i could create a profile on this thing!

As for the mechanic, I don't even want to speak about him!! I wish I had taken a good look at everything before I let him put his hands on it!

I was looking to a response from the forum before i sought any professional and probably costly advice, but it cant hurt to call up can it?

Glad to provide any more information

Hi MX51982
The link Old Dude provided is for the NB Series 2 (NB8B) manual
You might be better with the manual for the NB Series 1 (NB8A) which might be available from HERE

My initial guess is your mechanic has obtained an exchange head, possibly from a 323 or Laser and didn't swap the temperature sensor. (just a guess)

The oil sensor is near the oil filter on the block, sounds like he didn't reconnect it. (another guess)

If you could take some photo's of the sensor and the original connection and post them up, it may help the knowledgeable ones on the forum.

Dependant on what side of town you live, the best professional place to take it to would be the MX5 Factory in Ringwood although not a forum sponsor, they do support the Victorian MX5 Club.

bear in mind that you do have consumer rights. If the mechanic has not done the job correctly or treated you unfairly you can take it further. In Melb the MX5 Factory is one business that many seem happy with so perhaps make a note for the future. Incidentally the Haynes MX5 repaiir manual can be purchased easily or try your library.

Depending on your location, also Tony @ Fultech, Johnston St Burwood, 9888 7499; &
Max Kirwan Mazda, Bell St Preston, come highly recommended.

Pic of intake or driver's side of engine would also be useful in case the head has been replaced & the wrong head has been used.

OK, very valuable information. Strange that you might say he used a different head, he told me it was reconditioned. It would probably explain why 'my' head doesn't connect to my own temp plug. Not only this, but now i'm having trouble starting it, I feel like i'm trying to get a carby engine going. But bear in mind it only happens when its cold, if I finally get it going, it will start again and again, but say after one day it doesn't want to start again (without a fight)

Another interesting point is that when I switch to auxiliary, the oil gauge goes up, but when I switch the car on, it drops down as if it is not working.

Here is the pic, thanks for all the help.

It looks like you have the wrong sensor. It should have a 3 pin triangular plug like the one in your hand. Your starting problems could be cause by the sensor not being plugged in. That plug provides the ECU with the engine temperature as well as driving the temperature gauge. The ECU isn't getting a water temperature signal so it will be using a default setting, which is probably something close to the value from a warm engine. So if you go back to the olden days and carbies you are basically trying to start the car without using the choke.

I dont think your oil pressure gauge problem is related to the plug at the back of the head. The mechanic may have damaged some other wiring or left a connector off somewhere else. As others have said, the oil pressure sender is located on the drivers side of the block just above the oil filer. It is a single wire and probably easiest seen from under the car or through the wheel well. Check to see that it is plugged in and making a good connection.

Thanks a lot Garry, that is very helpful.

So I guess my best course of action is to source the correct plug from one of the Mx5 workshops? When I do get my hands on one, is it just a case of unbolting and replacing it with the correct one?

What I cant figure out is how it magically changed? But you are right that would probably explain why it's starting like a carby engine, might even explain the white smoke from the exhaust.

But could someone tell me if the oil gauge functions while the car is on? Mine must be connected if the needle moves upwards before the car is turned over, I just don't understand why it drops afterward.

I plan to empty the tank, run a tank of premium and hopefully clean the injectors/fuel pump at the same time.
Very valuable information guys thank you so much!

You dont need a new plug, you need the correct temperature sensor for your model MX5. I'd be going back to the mechanic that did the job and get him to put your original one back in.

My oil pressure gauge doesn't move until the engine starts running. So you have a wiring issue with your gauge or sender.

Look Ill do my best with the mechanic, but he is honestly not capable of fixing the problem, he is an idiot and I want as little contact with him as possible.

I have been calling up various people to try and track down the part. Can you please confirm that it is this plug which bolts onto the head that I require. In other words, a triangular plug to replace the rectangular one?

I am actually really suspicious that it is a different head, there is not way that this could have happened with my head!

mx51982 wrote:I am actually really suspicious that it is a different head, there is not way that this could have happened with my head!

If the temperature gauge worked before you had the head fixed then the photo proves 100% it's not your original head.

Either take it to your incompetent mechanic to get it replaced under warranty or take it to one of the business previously recommended and pay them to replace the sensor with the correct one.

IANTE here, but aren't the headgaskets different between the N/S engines and the E/W engines? I know some of the problems that that a couple of people have had with rebuilt engines (for the track) have been traced to incompatible head gaskets - apparently something to do with the water passages. How much of a problem that might be for a street engine I do not know.

Hopefully your man knows about this, and has not put a 323 head on with an MX5 gasket. Might be best to ensure that the head you have, and the gasket he put in, are a matching pair so to speak. If not, you may have a bigger problem than an electrical connection ...

You should be able to get the part number of the head gasket from the mechanic's order/invoice from his supplier.