When I turn on my heater I can smell exhaust.
Little help.
You need a mechanic to track down the exhaust leak. Simple.
Most likely a blown gasket or rotted pipe. This can be the exhaust manifold gasket leak, an EGR pipe leak, a rotted down-pipe or bad pipe gasket. Too many possibilities to pinpoint by long distance.
Plug your tailpipe(s) and see if the system will build pressure…If not, locate where it’s leaking and repair it…Your heater’s air intake is a screened grill near the passengers wiper arm post…Sometimes, engine oil leaks drip on the hot exhaust causing smoke that gets drawn into the heater intake…
Are you sure that it is really an exhaust leak. I’ve had some people claim this, only to find out what they were really smelling was burning oil, usually from a small valve cover leak.