How many Multifuels have been ruined because...

[Menaces Nemesis]

How many Multifuels have been ruined because of...

I've read posts on SS from folks making generalized statements like "the Multifuel is a weak design" or "they'll ventilate the block without warning" but I don't recall reading anything stating definitively whythe engine is to blame... i.e. bad metallurgy, poor castings, inferior engineering of specific components, etc. I've heard reasons like; lack of driver training, lack of maintenance, and just sheer abuse/over-revving. But I wonder if something else is at least partially to blame for the perception that Multifuels fail prematurely...

It was 91 degrees here today, and I cruised all over town with my radiator 1/2 blocked, and my temp never got above 180. Every time I drive my truck I go to great lengths to make sure it gets up to operating temp as quick as I can by completely blocking the radiator until 180 is reached, and managing how much is blocked thereafter (I've tested my thermostat, it opens right about 175) . And I make sure the temp stays at 180-200 for an extended time. As cold as our trucks tend to run, it makes me wonder if this doesn't have something to do with many Multifuel engines going bad prematurely from folks running them mile after mile, year after year, with the op temp rarely getting warm enough to prevent;

- The cylinders from getting glazed/scored because they didn't get warm enough for the rings to seal well, and got washed down with fuel.

-Oil from getting contaminated/acidic because it rarely got hot enough to burn off accumulated moisture.

-Bearings and shafts from getting briefly but repeatedly hammered under load when cold, while lubed with afformentioned contaminated oil.

I've also read things like; "Drive it like you stole it", "Run it up to redline for every shift", "Put a couple tons in the bed and run the piss out of it every once in awhile"...

If we make sure the engine is regularly ran at op temp, and isn't subjected to lugging or long periods of idling, do we really need to put our trucks through that kind of load to keep them happy? or can they live long lives at 180 degrees and cruising between 1500-2200 rpm?

I'd like to start a discussion here on this topic, and hear the thoughts of our resident Deuce Gurus on the subject. Thanks in advance for your replies. - MN

 

[cattlerepairman]

Interesting questions.
After a cold start, the massive cast iron block and heavy heads soak up a lot of heat until the coolant starts getting warm. Someone filmed the warm-up phase with a thermal imaging camera TIC and it showed how unequal the heat distribution is, causing stress on the head gasket. Pushing the engine at that stage can contribute to failures.

Once warmed up, though, the coolant is 80 degrees C / 175 degrees F which is what many other diesels run at, for hours and days on end. Once the engine has warmed up, I would think that, for the most part, it is at this temperature and above.

The permanently coupled fan is simple but certainly not up to today's standards. A fan clutch with a thermostat would make heat management easier. The multi runs perfectly fine without a fan for as long as you keep moving. I drove mine for weeks like that.
I can't say that the fan causes the engine to run "to cool", but others may chime in.

I did have the experience that you list, that after hauling gravel all day long for a project, the old LDT (before the swap) felt "happier" and definitely leaked less. I could see higher cylinder pressures also helping to seat the rings better. All within reason, of course, not a licence to beat the crap out of it.

 

[frank8003]

Just trying to save a Deuce.
The oil temperature would not go above 160 no matter how much load she carried.
I did put a coolant filter, and kept it topped off and clean coolant, put a new cap.
I found the wad of solder in the old thermostat during change out which jammed it open.

The coolant temperature is to be monitored but don't start driving it until one gets
the lube oil temperature UP. Use your heat gun.

 

[clinto]

Couple of thoughts.....................

It is my humble opinion, informed by my total lack of a mechanical engineering degree, that the engine is insufficiently robust and turns too many rpms. A stronger crank, stronger rods, better or thicker liners and an oiling system that doesn't starve the bearings on every cold start would make them last a lot longer.

I agree many of them run too cold.

I've also read things like; "Drive it like you stole it", "Run it up to redline for every shift", "Put a couple tons in the bed and run the piss out of it every once in awhile"...

People who say things like this are simply trying to justify their abuse of their machine, so they can have their fun without criticism. There is absolutely zero peer reviewed, engineer backed data that supports these statements, other than perhaps the tangentially related need to drive it hard enough to get it up to full operating temperature.

 

[quickfarms]

There is a lot of data that supports the issues resulting from not working diesels.

Wet stacking is a result of incomplete combustion.

 

[SCM35A2]

Subscribed!

 

[rustystud]

There is a lot of data that supports the issues resulting from not working diesels.

Wet stacking is a result of incomplete combustion.

Totally agree here. Diesel engines by their very nature need high pressure on the sealing rings to keep operating properly. Just running down to the grocery store doesn't cut it. You need a load and the engine needs to be at the proper RPM for that load for extended periods of time. Does "Menaces Nemesis" have a point about operating temperature ? Of course he does. Does just keeping the engine at that operating temperature keep our engines happy ? No. You need to load them down also. Now no one is suggesting you "abuse" your engine by taking it to the top of it's RPM range on every shift. That is just stupid and will more then likely get you a blown engine. But neither am I suggesting you "coddle" this engine.
About the oil pressure problems, yes this engine could do with some help. By going to the spin-on oil filters, I've reduced the time the engines oil pressure is low by seconds. You will never get immediate oil pressure though with this engine due to the oil pressure regulator being so far away from the oil pump. It literally has to travel over 4 feet from the oil pump to the regulator ! Really a crazy design, but it is what it is. I suppose you could go with a performance oil prepressurizing system like JEGS or SUMMIT Racing carries. I've found by just idling the engine when first starting until oil pressure is up works just fine for me. I also never rev the engine until it is warmed up.
Just a note about the quality of parts on this engine. The crankshaft is a forged steel unit. Not some cheap ass nodular iron garbage. The block is a high nickel alloy unit and the liners are industry standard. Not too thick or thin.
Remember that tractor pull guy I reached out to ? Tracey Varns . He saw the potential in this engine and used to pull out 500 HP from the stock engine block (after modifying it of course) . He still used the stock crankshafts (after some modifications) in his 5,000 HP engines. So the crankshafts are not a problem in this engine, neither is the block.
Now coolant flow has been a problem especially in the back by piston number 6. By keeping the coolant clean and the block free of debris (especially casting sand) you can help this problem area.
So after all is said and done, by just running this engine like it is suppose to (warm up before use) and keeping proper maintenance up, this engine should not be a problem.

 

[MikeON]

There were some old threads about failure of connecting rod bolts resulting in block ventilation.
Here is one of them but I think there were more threads:
https://www.steelsoldiers.com/showthread.php?103279-Rod-Bolts&highlight=rod+bolt+block

 

[frank8003]

I think some drivers never had the instruction. The one about the torque peak at around 1800 rpm, the one about proper warm ups and shutdowns, the one about don't lug the puppy, and the one about high revs that are unnecessary. Most of the engines that now exist have the original harmonic balancer, think about that too.
So, some pictures for the General.....
View attachment PS magazine Issue 356 July 1982 turbo.pdf

 

[papabear]

I think some drivers never had the instruction. The one about the torque peak at around 1800 rpm, the one about proper warm ups and shutdowns, the one about don't lug the puppy, and the one about high revs that are unnecessary. Most of the engines that now exist have the original harmonic balancer, think about that too.
So, some pictures for the General.....
View attachment 729600
View attachment 729601

I think Frank8003 has posted the right combination on the data plate. I do this start/shutdown procedure on ALL my diesels....trucks, backhoe, forklifts, even the zero turn John Deer mower. Sometime I even idle them a little longer if they have been on a long run or been working them hard. Of course all systems need rto be in proper working order to prevent failure.

 

[WillWagner]

First, blocking the radiator during warm up...before stat opens....kinda does nothing. Remember, these systems have two circuits, block loop and cooling loop. When the stat is closed, coolant is shunted back into the block via the block loop, the seal in the thermostat housing prevents coolant from going around the stat to the radiator. When the stat opens, the bypass loop is blocked by the stat body forcing the coolant through the radiator. The bypass loop is designed into the system to aid in warm up due to the CI engine having a colder ignition than a gas engine....cold start a gas engine and a diesel engine, lay a finger or two on the exhaust manifold and see which one you can keep touching longer....Also, removing a thermostat is not a good thing in a 2 loop system, the coolant will take the path of least resistance when circulating, which would be through the block loop. This can cause an overheat if the engine is loaded without a stat.

Up where you live, a winter front after warm up is a good thing due to the direct drive fan, It will help the engine oil and coolant stay at a more constant temp instead of bouncing all over the place from the stat modulating.

The oiling system, I agree with Rusty, there is a l o n g path for the oil to travel, and upgrading to spin ons with anti back flow helps noticeably. IIRC, the time to get op with the can filters was somewhere around 8-10 seconds. With the spin ons it was, again IIRC, it has been a while, dropped to around 4 seconds. Remember though, after the engine is shut down, the pressured oil in the galleys stays there, the pressure goes away because there is no nothing turning to make pressure, but the oil is still in the galleys and on the bearing/crank/component bearing surfaces. On first start, there is still a protecting oil film on all pieces parts, just no real flow until the lube pump force feeds all the passages so pressure can be made. The no flow thing is in my opinion what can lead to lower rod end failures if operator A doesn't let the engine do what it was designed to do before stepping on the throttle, the data plate above kinda says it all. Also remember, oils have come a long way since these engines were designed, they seem to protect things a tad better and suspend the particulates better. I think the combo of newer oils and spin on filters is a win on these.

The whole idling to warm up thing can cause other issues. Not only the multi, but other engines too, long idle times do cause oil and or fuel slobber out the manifold joints, turbo outlet and in worst case scenarios, out the stack. As Rusty said, the grocery getter type of use does these engine no good, I think this is where the "drive it like you stole it" thing came into play, to clean things up and get the power cylinders all sealed up the engine needs to be worked, the only real way to do that is to load it and drive it. Most people here don't use the engine as it was designed, that's why there are threads about smoke, slobber out there.


IIRC, these like 2000 to 2600 RPM, pulling it down to 1500 would be lugging it. I don't think trying to operate the engine at 15-1800 RPM would do the engine any good, not to mention even slower road speed.

If you look at these engines and compare them to the other engines made at the time, I think they are on par. I have had my hands up inside a few engines and the multi is built as others of it's time are/were. IMO, the reasons there have been ventilated blocks is, 1, newer operators don't realize the engine is old school, they might think it is OK to fire it off, put it in gear and go. Old things like to get up and going a little slower than younger things. Start the pig and go get a cup of coffee! 2, most of these trucks have had multiple owners, from .gov to municipalities to farmer Bob. Who knows what kind of maintenance or lack of has been done on these.

DAMM, I kinda miss my truck. I do get to see it when Blisters post pics of it....

 

[Menaces Nemesis]

Another question that comes to mind is, bear with me here; I understand that if the Multifuel is left to idle and putter for long periods, it will wet-stack and slobber as other diesels will, and a "typical" diesel engine needs to be worked continually in order to generate enough pressure in the combustion chamber to force the rings to seal well. However, it's written that the Multifuel's abnormally high compression ratio is what has led to head gasket failures (along with less-than-stellar weep-tab/fire-ring type gaskets). So, since the Multi's pistons/rings are already exposed to higher combustion chamber pressures than the typical diesel engine, simply due to the higher-than-normal compression ratio, would this offset the need to put the Multifuel under as much load as a typical, lower-compression diesel needs to be, in order to keep the engine healthy?

I don't know how the effect of better chamber sealing due to higher compression ratio could be qauntified, but it seems like there would be at least some positive effect.

 

[rustystud]

Another question that comes to mind is, bear with me here; I understand that if the Multifuel is left to idle and putter for long periods, it will wet-stack and slobber as other diesels will, and a "typical" diesel engine needs to be worked continually in order to generate enough pressure in the combustion chamber to force the rings to seal well. However, it's written that the Multifuel's abnormally high compression ratio is what has led to head gasket failures (along with less-than-stellar weep-tab/fire-ring type gaskets). So, since the Multi's pistons/rings are already exposed to higher combustion chamber pressures than the typical diesel engine, simply due to the higher-than-normal compression ratio, would this offset the need to put the Multifuel under as much load as a typical, lower-compression diesel needs to be, in order to keep the engine healthy?

I don't know how the effect of better chamber sealing due to higher compression ratio could be qauntified, but it seems like there would be at least some positive effect.

Interesting question. Need to think about that.

 

[WillWagner]

Don't know. I am unsure of the type of ring that the MF uses. Ring designs have changed over the years as technology has advanced. Older engines, most all of them, had issued with slobber, wet stacking, passing oil past rings and guides when operated in a low/no load condition due to ring design...keystone, reverse twist, non keystone, whatever, and usually no valve seals used....on Cummins engines anyway.

I think the comp ratio is an ignition process and the higher ratio makes it a tad more efficient, remember, a compression ignited engine only uses the air being compressed and fuel atomized at the correct time to start the fire in cylinder, no external ignition sources.

I think what makes the cylinder seal more efficiently is the rate of fire, heat and increased cylinder pressure. Figure a 6 cylinder idling at 1000 rpm has around 3000 power strokes per minute, divide by 6, that's about 500 per min per cylinder, 8 times a second. It has, usually no manifold pressure, no vacuum, the cylinder is being filled by no/low pressure, atmospheric pressure. As the unloaded rpm comes up, the rate of fire increases but only a tad more fuel is used, only to sustain the RPM, still no real pressure or heat is in cylinder. When the engine is loaded, the fuel increases along with the volume of air increasing heat and pressures and components in cylinder make optimum sealing.

I think the original multi piece head gaskets were either a "new" design that was thought to be better than what was available at the time or a cost saving. If you look at the original gaskets there are zero sealing features around any coolant or oil passage, the "spacer" was just a fiberglass or whatever board with no way to really compress. The fire ring just a steel or alloy ring. As the engine surfaces moved around, things find a way out from where they were supposed to be because of design of the gasket. If you compare a new, current gasket to the old ones, you will see seal rings/strips around fluid passages and a gasket material that is able to be compressed allowing for a better seal everywhere there is fluid or compression.

Cummins did a multi piece head gasket on the first generation of 15L ISX engines. They had separate grommets that were put into the fluid passages and a separate seal ring for compression along with a grooved top liner for the seal ring to sit in. It was a horrible failure. The fluid passage inserts didn't fail, the compression ring did. When it did, compression found it's way over the ring, eroded the head casting from high pressure/frequency gasses passing through a small area ruining the head then they found the path of least resistance which was usually the coolant passages next to the liner causing compression in the cooling system. It was a major fiasco. The fix was flat top liners and a normal style head gasket

 

[fasttruck]

I got over 35,000 miles on the turbocharged variant used in M52A2s and every thing I did with it was heavy. It survived by not being lugged or over reved. Only problem was blew out head gasket at rear of engine twice(furthest away from the water pump). By then we were getting in M818s and I was advised to pick one out as the last time the shop changed the head gasket was the last time.M818 also went about 40,000 mile before I retired. As average military driver does not bring this level of skill or concern to the table, these performance marks are not always achieved.

 

[rustystud]

Don't know. I am unsure of the type of ring that the MF uses. Ring designs have changed over the years as technology has advanced. Older engines, most all of them, had issued with slobber, wet stacking, passing oil past rings and guides when operated in a low/no load condition due to ring design...keystone, reverse twist, non keystone, whatever, and usually no valve seals used....on Cummins engines anyway.

I think the comp ratio is an ignition process and the higher ratio makes it a tad more efficient, remember, a compression ignited engine only uses the air being compressed and fuel atomized at the correct time to start the fire in cylinder, no external ignition sources.

I think what makes the cylinder seal more efficiently is the rate of fire, heat and increased cylinder pressure. Figure a 6 cylinder idling at 1000 rpm has around 3000 power strokes per minute, divide by 6, that's about 500 per min per cylinder, 8 times a second. It has, usually no manifold pressure, no vacuum, the cylinder is being filled by no/low pressure, atmospheric pressure. As the unloaded rpm comes up, the rate of fire increases but only a tad more fuel is used, only to sustain the RPM, still no real pressure or heat is in cylinder. When the engine is loaded, the fuel increases along with the volume of air increasing heat and pressures and components in cylinder make optimum sealing.

I think the original multi piece head gaskets were either a "new" design that was thought to be better than what was available at the time or a cost saving. If you look at the original gaskets there are zero sealing features around any coolant or oil passage, the "spacer" was just a fiberglass or whatever board with no way to really compress. The fire ring just a steel or alloy ring. As the engine surfaces moved around, things find a way out from where they were supposed to be because of design of the gasket. If you compare a new, current gasket to the old ones, you will see seal rings/strips around fluid passages and a gasket material that is able to be compressed allowing for a better seal everywhere there is fluid or compression.

Cummins did a multi piece head gasket on the first generation of 15L ISX engines. They had separate grommets that were put into the fluid passages and a separate seal ring for compression along with a grooved top liner for the seal ring to sit in. It was a horrible failure. The fluid passage inserts didn't fail, the compression ring did. When it did, compression found it's way over the ring, eroded the head casting from high pressure/frequency gasses passing through a small area ruining the head then they found the path of least resistance which was usually the coolant passages next to the liner causing compression in the cooling system. It was a major fiasco. The fix was flat top liners and a normal style head gasket

I remember that Cummins head gasket system very well ! It was a pain just to install them correctly the first time, let alone to have to do it again and again due to failures.
Your right about the engine and the amount of fuel and heat at a no load and loaded condition. If I had been thinking correctly last night I would have remembered that.

 

[Menaces Nemesis]

Just west of where I live, I-70 starts it's ascent into the rockies. It's a nice long steep grade that requires the peddle mashed to the floor to maintain any decent road speed. I'll start having lunch out that way and taking the truck up that hill regularly to keep the rings more acquainted with the cylinder walls (along with keeping the radiator fully blocked until op temp is reached when heading out). I've read posts from SS members stating their trucks rarely get to/above 160 degrees. I'm hoping this thread encourages those folks to gently get that temp up to 180 every time they drive the truck, and try to give it some reasonable excercise if it hasn't had any in awhile.

Many Thanks to Everyone for your replies!

 

[dmetalmiki]

Some good pointers.
I drive my vehicles with respect. 1800 rpm for changes. 2000 rpm cruise.
All my trucks have the radiator muffs on and closed.
Start up And shutdown are under 'pressure'.
I feel happier, comfortable with that procedure.

https://youtu.be/IBE5Bg67UeE

 

[Menaces Nemesis]

Some good pointers.
I drive my vehicles with respect. 1800 rpm for changes. 2000 rpm cruise.
All my trucks have the radiator muffs on and closed.
Start up And shutdown are under 'pressure'.
I feel happier, comfortable with that procedure.

Hey dmetalmiki, what's your shift from 3rd to 4th like? I'd imagine my Spicer 3053A is similar to others;... I normally shift 2-3 and 4-5 at 2000-2200, but I run it up to 2500 in 3rd gear when shifting to 4th, and that still drops the RPM way down to 1500 when I let the clutch out on 4th gear (this is why I claimed 1500 to be the low RPM point in the opening post, and I'd be apprehensive about going any lower). And my truck seems to upshift into 2nd much easier if 1st gear is only used to give just a little more than a nudge to give the wheels a few rotations (maybe 1500 RPM, along with a complimentary double-clutch into 2nd) any more than that and I'll be "arguing" via the shift lever with the "grumpy old man" that's bolted behind the bell housing (He doesn't like to be rushed when starting out, and I let the 'ol boy have his way - MN

 

[rtadams89]

I'm hoping this thread encourages those folks to gently get that temp up to 180 every time they drive the truck, and try to give it some reasonable excercise if it hasn't had any in awhile.

Now you guys have me thinking about getting a winter hood blanket here in AZ!