I would greatly appreciate any help or advice on my 88 420 SEL. Recently it has quit reliably been producing heat. It hasn't quit completely but randomly makes heat or heats during warm up and then stops as soon as I put it in drive. The radiator has just cracked on the top by the overlow hose and I'm in the process of replacing it. Ther is also a ticking sound coming from the right head which worries me. Any insight would be gratly appreciated. Thanks

 

Intermittant heat could be caused by low coolant level.

 

Thanks for the respnse. I appreciate any help. i had kept on eye on the coolant level though and it has always been at the recommended level. Any other ideas? Thank you.

 

Thermostat sticking open?
While the heater is inconvient, I'd worry more about the ticking sound from the head. Could be a lack of oil getting up to the head - either low on oil or the oil pump failing.
I'd take it into a shop for to have it looked at and to get an estimate as soon as you reasonably can.

 

Check themostat and Monovalve.