Thermal Reactor

[darrylrevok]

I purchased a 1978 530i a few months ago and it's been sitting in my back yard ever since. I have not yet saved the funds to get it on the road. I am unfamiliar with most of the mechanical workings of the engine, and I was wondering if there was a surefire way to tell if this 530i does indeed have a thermal reactor installed. The dash light is illuminated, indicating that the reactor needs to be serviced, but I'm not sure if a reactor is present. I was told by the previous owner that the engine had been swapped out and I'm not sure if the reactor was taken out. Is there a way to tell if there is a thermal reactor present without taking the engine apart?

[Mike W.]

A thermal reactor is kind of an exhaust manifold, except different. A conventional exhaust manifold is cast iron. A thermo reactor is kind of like a tin can with cast iron flanges. It also has a smog pump with air injection into it. The first image is a thermo.



The next a manifold.



You just have to look at it to tell, it could have been left in place or replaced with manifolds.

[Luis A.]

This is what the reactors look like. Note the smaller diameter air pipe running on top of them.

[Blaise]

By the way, the service light is turned on based on mileage and has nothing to do with the condition of the thermo-reactor (if you have one). What I mean is that there is no sensor on the reactor, just a mileage based box that ties the warning light to the speedo cable. There should be a reset button on that box, which is in line with the speedometer cable and can be seen under the car.