Rough Running

[winners]

I've been trying to get to the bottom of my S1's rough running. New points and plugs helped significantly. My problem is it runs fine for 30 mins or so then it appears to get too hot. The temp guage shows nothing unusual but the fan kicks in and the car stars mis-firing. Could it be a thermostat stuck or something else?

[molemot]

Might be an air lock...try bleeding the cooling system, there should be a bleed screw on the radiator, accessible through a hole in the front boot by the LH front wheel arch. Get it hot, loosen the bleed screw and let the air out..be careful as it'll be H-O-T!!

[matk]

Does it start misfiring exactly when the fans come on? You can test by shorting across the Otter switch? Try it from cold? If so perhaps the fan circuit is shorting out something else in the engine bay when live?

[Choppa]

Might need to get it burped to clear the air lock, Molemot's suggestion is the usual way, but there is a thread about this on here somewhere, where someone ended up jacking up the rear end to get the air lock cleared

[USAndretti42]

Following on from Matt's post, what does you voltage do when the fan cuts in? It could be dropping because of a short or just because the alternator can't keep up and making the voltage too low for the coil to work well.

[dglotusltd]

And now for something completely different........

If the carbs are out of balance the engine can run hot. Had a similar missing issue which got really bad once it was warm. Got myself a 4 tube manometer....(two Dellortos) and spent some quality time balancing the carbs. Turns out the engine was running almost entirely on the front carb.

Of course I did this AFTER verifying I had no air leaks or manifold leaks...etc.....

DomG

77 S1 Esprit