6.9 Block Heater Cracking Issue

[OleRed]

Howdy y'all!

My '85 F-250 6.9 is a really, really hard starter in the cold (takes a lot of cranking). Glow plugs are fine, new injector pump is in, etc. Still need to get a compression test and try to figure out the main issue (she's a bit of a hard starter on warmer days too, but nowhere near as bad as when it's below 30).

The motor's got a block heater installed, but I'm not sure if the '85 castings (exact build date is September 1985) are prone to the block cracking issues caused by block heaters of previous years. I've combed through multiple forums trying to find out about the '85 without much luck. If my block is prone to that issue, I'll just end up going with a heater wrap for the fuel filter or something along those lines, at least until I can figure out the main culprit behind the hard starts.

Any help is much appreciated

[old55pete]

There are different kinds of block heaters besides the ones that go in a freeze plug in the block. I have a 90 with a 7.3 IDI in it. when the block heaters went bad, I put one in the heater hose( got it from NAPA). it has a pump inside of it and it heats and pumps hot coolant through the whole system. This means that the heater and defroster work as soon as you start the pickup.

The reason I did this is not because of the block cracking issue as I have heard of that. The reason I did it is that it only took about an half hour to install instead of the several hours to half tear the pickup apart to replace the stock ones.

Just an FYI

[kramttocs]

I haven't heard of that with the 6.9's but I don't follow diesels much.

Just googled it and found a good (last) post in this thread by a 'familiar face':

https://www.ford-trucks.com/forums/1473507-6-9-block-casting-number.html

Sounds like there may be a few visual indicators you can look for.

I agree with Steve in that the circulating heaters are nice. We have a couple of those on our gas tractors.

[jdavidsmi]

I haven't heard of that with the 6.9's but I don't follow diesels much.

Just googled it and found a good (last) post in this thread by a 'familiar face':

https://www.ford-trucks.com/forums/1473507-6-9-block-casting-number.html

Sounds like there may be a few visual indicators you can look for.

I agree with Steve in that the circulating heaters are nice. We have a couple of those on our gas tractors.

When we were stationed in Alaska, my 76 f250 came with a block heater, and it just did not do the job. I installed a heater hose heater. Worked like a charm, and most of the time no problem turning the motor over. We also had a heating plate glued to the transmission. And an electric heater in the cab.

There were a few days every winter, when it was down to -50 or so, we had to use the kerosene heater to blow hot air under the truck, so it could be steered.

We also used the heater hose heaters on all our vehicles when we lived in Vermont.

 

[ArdWrknTrk]

When we were stationed in Alaska, my 76 f250 came with a block heater, and it just did not do the job. I installed a heater hose heater. Worked like a charm, and most of the time no problem turning the motor over. We also had a heating plate glued to the transmission. And an electric heater in the cab.

There were a few days every winter, when it was down to -50 or so, we had to use the kerosene heater to blow hot air under the truck, so it could be steered.

We also used the heater hose heaters on all our vehicles when we lived in Vermont.

I don't know why block heaters are bad, but U-techcenter has 3 available OEM core plug heaters for $20 + $5 shipping.

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F164130558968

[old55pete]

I don't know why block heaters are bad, but U-techcenter has 3 available OEM core plug heaters for $20 + $5 shipping.

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F164130558968

Jim, I dident say they were bad, I just said that they are a PITA to change while the engine is in the pickup. As in half pulling the engine to replace them PITA. That being said, I told him about an easer replacement that works as well, or I think, better, and takes less time as long as the old block heater is not leaking.

[kramttocs]

When we were stationed in Alaska, my 76 f250 came with a block heater, and it just did not do the job. I installed a heater hose heater. Worked like a charm, and most of the time no problem turning the motor over. We also had a heating plate glued to the transmission. And an electric heater in the cab.

There were a few days every winter, when it was down to -50 or so, we had to use the kerosene heater to blow hot air under the truck, so it could be steered.

We also used the heater hose heaters on all our vehicles when we lived in Vermont.

Ugh, I can't imagine that kind of cold or maybe don't want to.

Jim - nothing wrong with block heaters (unless using them with a prone-to-crack block I guess ). They just don't work the same and thus have a different level of effectiveness when compared to the circulating type.

Here in the midwest where the cold is nothing compared to David's experience, we use the factory block heaters in our diesel tractors/farm trucks and they work fine for starting assistance.

[ArdWrknTrk]

Ugh, I can't imagine that kind of cold or maybe don't want to.

Jim - nothing wrong with block heaters (unless using them with a prone-to-crack block I guess ). They just don't work the same and thus have a different level of effectiveness when compared to the circulating type.

Here in the midwest where the cold is nothing compared to David's experience, we use the factory block heaters in our diesel tractors/farm trucks and they work fine for starting assistance.

Yes, I was saying 'i don't know' but if this type of block heater causes cracks, that's not good.

I can understand why a circulating heater would be better!

Anyway, I spotted these and thought it germane to the conversation...

I'm not sure what the factory ones cost, but $25 seems a good deal.

 

[Ford F834]

As Scott has already pointed out, there is a chart showing serial number breaks for changes made to the 6.9’s.

The problem is, it does not directly state anywhere “this is where we improved the casting around the block heater boss”. The following information is copy-pasted from another forum, but should help:

6.9L and 7.3L Core Identification

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

7.3L Block

Block Casting Number: 1809000 C1

Visual Identification: *Same as 6.9L new style block

*Head bolt ribs on side of block extend from pan rail to head gasket surface or rear two head bolts left side

Head Bolts: *1/2" - 12 point socket is used to torque head bolts

*Block tapped with 1/2 - 13 for head bolts

My understanding is that the problem blocks (for block heater cracking) were found in 1983 and very early 1984 trucks. Mine was a 1986 so I brushed it off and used my block heater all the time. Later I discovered the engine was not original, and mine was a very early s/n. Oooops.

I have read if you use a block heater on an early 6.9 that you should consider plugging it in while the engine is still warm. I have also read that you might want to consider a lower wattage heater (they are available in several wattages). I have seen the radiator hose heaters, but I have no idea how they work on a 6.9 without a pump to circulate it through the block. I do know that the stock block heaters work very well. There is nothing like an easy start plus instant warm air out of the vents when it is below zero outside 🥶.

[Ford F834]

As Scott has already pointed out, there is a chart showing serial number breaks for changes made to the 6.9’s.

The problem is, it does not directly state anywhere “this is where we improved the casting around the block heater boss”. The following information is copy-pasted from another forum, but should help:

6.9L and 7.3L Core Identification

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

7.3L Block

Block Casting Number: 1809000 C1

Visual Identification: *Same as 6.9L new style block

*Head bolt ribs on side of block extend from pan rail to head gasket surface or rear two head bolts left side

Head Bolts: *1/2" - 12 point socket is used to torque head bolts

*Block tapped with 1/2 - 13 for head bolts

My understanding is that the problem blocks (for block heater cracking) were found in 1983 and very early 1984 trucks. Mine was a 1986 so I brushed it off and used my block heater all the time. Later I discovered the engine was not original, and mine was a very early s/n. Oooops.

I have read if you use a block heater on an early 6.9 that you should consider plugging it in while the engine is still warm. I have also read that you might want to consider a lower wattage heater (they are available in several wattages). I have seen the radiator hose heaters, but I have no idea how they work on a 6.9 without a pump to circulate it through the block. I do know that the stock block heaters work very well. There is nothing like an easy start plus instant warm air out of the vents when it is below zero outside 🥶.

One more thought... if your glow plugs are working yet you are having difficulty starting, it could be your starter isn’t turning the engine over fast enough. This could be weak batteries, poor cable connections, or a weak starter motor. The decline can be gradual so that you don’t notice it, and in cold weather it does not have to turn all that much slower than normal to give you starting problems. I have thought mine was cranking just fine (but no start) and after cleaning the cable terminals and grounds it would fire right up. If I remember right Ford said the 6.9 should start on glow plugs alone down to around 10*F and some owners brag that theirs will start on only GP’s in below zero weather. I prefer the block heater whenever electricity is available, but it shouldn’t be a requirement unless the temps are very low...