I took my truck to the shop to replace the glow plugs because they used autolites the first time and they burnt out within 2 weeks of getting the truck back from the shop. Im guessing they replaced them with autolites again which im not happy about considering they are probably just gonna end up burning out again, but thats another rant.
They checked my block heater, they said when they had the truck back in October the heater was working but now its not. I havent even touched the heater so im confused why its not working but more importantly Im concerened about the heater cracking the block, thats a common problem with the pre 85.5 6.9s right? Im pretty sure I have a 6.9 with the weak reinforcement around the heater. The mechanic said that he has never seen a 6.9 with a cracked block from the heater, but then again he also said he has had no problems using autolite glow plugs. When we bought the truck the previous owner said he had used the heater before and my block is just fine. Im really confused here, am I in a warm enough climate that I can get away with using the heater when its cold or was the previous owner just lucky? I wasnt really having a problem starting the truck with either, it would start rough and spit smoke for 5-10 minutes but it would start. The glow plugs would help in that department but I know a heater would help to. But Im thinking why chance it? What do you guys think?

 

Dave S. has posted theserial numbers when they changed the block.
When I have had trouble with the parts a mechanic and go back and he says he has never had trouble I tell them you have at least once that I know about.
Now he may not have been lying about the block as I had never seen one until I bought one in wyoming and I had been dealing with them since they came out in 83,and didn't know it was common until I came to this forum.
I would bet that if you only used it when it is real cold and 2 hours is all you need it will handle it.

 

Let's see, they replaced them with Autolite plugs, and they burnt right out.

Now they are replacing them again, are you paying for it?

If you are, then they obviously don't have a problem, taking your money.

My Motorcraft plugs have been in my engine for four years, still fires right up in sub zero temps without plugging in.

Mid year 85 was when the block casting changed.

6.9 blocks up to serial #u2u17900 had a thinner casting around the block heater. It is very common for these blocks to crack.


6.9L Old Style Block

Block Casting Number:


On left side of block (beneath oil cooler) 1805440C1
Note: Some 440 blocks are truly new style and must be visually inspected by raised donut around the block heater, frost plug (right rear). Old style below serial number 173828.
Visual Identification: *No counter bored area for block heater
*No defined area on side of block for dip stick
*Thickness of cast iron around block heater 3/8" (.375")
Head Bolts: *7/16, 12 point socket is used to torque head bolts
*Block tapped with 7/16-14 for head bolts

6.9L New Style Block

Block Casting Number: 1807996C1 Note: Some new style blocks have casting
number 440. Above serial number 173828.
Visual Identification: *Has counterbored area for block heater
*Very defined relief area cast in side of block for dip stick tube.
*Thickness of cast iron around block heater 15/32" (.470")
*Latest style (not all new style 6.9) has ribs around head bolts, rear two on left side go from head gasket surface to pan rail - same as 7.3
Head Bolts: *Same as old style 6.9


As far as how often the blocks crack, not really that often.
But on the other side of the coin, if it cracks the block is scrap metal.
So I guess it boils down to how lucky are you?

My luck, it would crack the first time I plugged in.

 

The shop replaced the plugs with autolites before I had found out that you had to use the motorcraft plugs. The only reason we took the truck back to the shop was to try and see if they would replace them with motorcraft plugs, but they are convinced that the autolite plugs are just fine, they shouldnt be charging us for anything on the plugs if they are im gonna be pissed. Im just gonna replace the plugs with motorcraft plugs when we get the truck back and that will be the end of it. The mechanic says "these trucks really need a block heater" which my dad fully believes so he is having them put the heater in, but that $150 would buy alot of the correct motorcraft plugs which would solve the problem, the more I think about this the more frustrated I get .

 

If your glow plug system is working properly you can start the truck even at 10 deg but it will let you know not to drive it until it gets warmed up. Plugging in helps with the wear on the starter (big $$) and on the engine. Also very easy start in very cold weather.

 

If I were installing a block heater in an early model 6.9 I would try to use one of the smaller wattage heaters.
I have seen block heaters from 500 watts up to 1500 watts.

Even better would be a remote heater so the coolant could circulate through the block.

And I do not know the part number, but International did have a heater that screwed into the coolant port on the oil cooler.

My guess on the glow plugs, no warranty on electrical parts and they will want paid again.

 

Like a heater that you splice into a coolant hose right? I have one on my 4 cylinder Isuzu truck but Im not sure why since its a gas lol, I guess cause the carb doesnt like the cold. Thats a good idea, are those things pretty cheap? I called the shop today to have them not put in the heater but it was to late they already had it in, I wish I wouldnt have even taken the truck back to them, I should have just bit the bullet and put the motorcraft plugs in myself. The mechanic said he put napa plugs in but Im guessing they will go out just the same as the autolites.

 

Is it OK to leave a block heater plugged in continuously, like for days? I've got a 7.3L....

 

Barely smokin it is not ok in the early 6.9 blocks they have a block cracking issue.
Plugging them for days also is very noticible on your electric bill.

 

It will increase the electric bill. You can get a timer and have it turn on the power 3 hrs ahead of needing to start it.

 

My 7.3 has been left plugged in for a few days at a time, other than the power bill, no damage. Sometimes it has been an error, others it was due to being on call for various jobs etc.

 

Searching the NAPA site, Autolite, Champion, AC Delco, NGK, Echlin Fuel Systems, Delphi Engine Managment and Altrom are the glow plug manufacturers they carry.

Out of that list, Echlin looks like it might actually be a Beru plug, can't quite make out what it has printed on the plug.