Hello, I have a 79 300d which came from Texas with no block heater. Now it resides up here in Toronto. With winter coming, I was planning on installing an inline block heater. I need to know what is the inner diameter of the hose so I get the proper size.

Block Heater
 

Don't waste your money on a radiator hose heater. They will only heat the water in the radiator.Get the block heater for around $40 and have it installed.You'll be glad you did.
Bill Lewallen Lexington,Ky.

I did check with Mercedes Benz Canada, and they wanted $90 cdn for the block heater, and 4.5 hrs labour @$90/hr to install. Plus! - they advised me that they would not be responsible for any leaks that were derived from the installation. Add taxes and the bill is easily $700.00. Ugh!!!

I have seen heaters that are large magnets with a power cord. They are meant to be removed from the engine when you are driving. I have no idea if they work or not.

My '79 300D starts OK down to -20C (-2F) without a block heater. I use 5W30 and have parallel glow plugs. The 4.5 hrs shoptime seems about right.

Gary

Block heater
 

Four and a half hours to install a block heater on a 300D is too much time. Give me a helper and I believe we can remove the engine and transmission in that time.
Bill Lewallen

Wm. Lewallen, I'll have to agree that 4.5 hrs is too much if you are familiar with the car. I don't know what I was thinking, but what I meant was the time it would take me to figure it out for the first time. Once you get the starter removal figured out, I don't know how difficult the frost plug removal is. Can't be that bad. I would definitely try this job myself if the block heater quit working or the car didn't already have one.

On a similar note, a shop once quoted me 2.5 hours to replace the front end upper control arm bushings. It looked like a tough job, never having worked on a front end before. After completing the job myself, I think I could easily do the job in 1.5 hours or less.

Removing the plug is a chore.
I put one in my old 300D, and used a 36" breaker bar. I almost gave up, but it finally began to turn.
If your car has a lot of mileage, the plug may need some heavy torque to get it out.

I do agree, a block heater is a nice thing to have. I personally do not use mine unless the temps go below zero F. I have always been able to start mine by simply glowing an extra time or two, and then starting her right up.

Good luck with your installation

Anyone know the ID for the hoses leading to the ACC servo?