Keeping a cool head

flash7210 · **Posted:** Thu Jan 07, 2016 11:25 am

The discussion about the Stant thermostat got me thinking about how coolant flows through the engine.

The water pump pushes coolant through the block and up through the cylinder head. With one exception, all coolant leaves the engine through the head. The one exception is the oil cooler where coolant leaves the block, goes through the oil cooler, and then back into the water pump.
The majority of the coolant leaves the head through the thermostat housing and from there can follow several paths:
1. out to the radiator
2. through the bypass, back down to the water pump
3. out to the heater core and back down to the water pump
4. out the small de-gas line and up to the coolant tank

There are also two other possible coolant outlets on the drivers side of the head. One, between cylinders 3 and 4, is plugged. The other, between cylinders 2 and 3, would feed the EGR cooler (and then back to the water pump).

Is it possible that all reported cases of cracked heads and head gasket failures are due to insufficient coolant flow through the head?

Its difficult to go back and search though all the posts and find the exact mechanisms for head/gasket failure. Most just say "my head is cracked" or "I blew a head gasket" with no further details about exactly where on block/head the failure occurred.
In my case, the head had cracks around the exhaust valve seats of cylinders 2, 3, and 4. And there have been a few other reports of similar cracks around cylinder 2 and 3 or 3 and 4.
Why not cylinder 1?
Is it because cylinder 1 is closest to the thermostat housing and therefore receives better cooling?

The head gasket is designed to allow more coolant flow through the rear most cylinders and restrict flow through the front most cylinders. This is supposed to help balance to cooling across the entire head so that cylinder 4 isn't hotter than cylinder 1.
But like most things, this design is not perfect.
Cylinder 4 will always be a little hotter than #1 because its last in line to receive coolant.

The engineers put those two coolant outlets on the drivers side of the head for a reason and I doubt that its because of the anticipated need for a EGR cooler.
Could it be that those ports are there as a additional coolant outlet to promote balanced head temperatures?
For those that have deleted their EGR coolers, is it wise to block that port in the head?

I dont have the answers for that, just leaving it open for discussion.

And just one more thought about the engine thermostat.
Could a stuck open thermostat promote unbalanced head cooling by allowing cylinder 1 to cool faster than #4?

olypopper · **Posted:** Thu Jan 07, 2016 2:29 pm

"The engineers put those two coolant outlets on the drivers side of the head for a reason and I doubt that its because of the anticipated need for a EGR cooler.
Could it be that those ports are there as a additional coolant outlet to promote balanced head temperatures?
For those that have deleted their EGR coolers, is it wise to block that port in the head?"

One thing you have to remember is that even though this engine is small, it was designed as a light duty "semi-industrial" engine. It's used in boats, small automobiles and probably a few other things. If those ports were actually meant for cooling the head, we can reasonably agree that there would be some sort of permanent ducting for the coolant to circulate.

I suspect they are simply additional ports for cooling options for additional components like the EGR cooler, manifolds when used in different applications, etc.

flash7210 · **Posted:** Wed Mar 30, 2016 7:17 pm

I'm brining this back to the top due to recent discoveries of dropped vales with no indication why.
So far, all reports of broken valves have been at cylinders 3 and 4.
I have never seen any reports of broken valves at cylinders 1 or 2.

Mountainman · **Posted:** Wed Mar 30, 2016 8:23 pm

I thought I read that the marine engines have a different (iron) head? I know i read that the block is the same. Maybe Lacabera or other members across the pond know?

I can say this, I overheated one CRD to the point of boiling over once, and ran it up to 3/4 on the gauge multiple times, and it didn't crack the head (I'll be checking if it's warped soon as it's sitting on the bench), but it did develop a really slow HG leak (I guess it could possibly be cracked, but the machine shop will tell me soon enough). FWIW

dkenny · **Posted:** Wed Mar 30, 2016 10:02 pm

are these problems only in the US..
how have these problems in the rest of the world?
just asking..not done the digging..i think others already might know.
i'm sure the EGR required in the US it hurting these engines..its not the EGR concept
it self..but dumping soot filled air post air filter..lets just dump a bunch of sand filled air in you intake..post filter..
duh! not a good idea..dump a bunch of soot fill air pre-filter..so? need to change the air filter more often..or use an oil bath filter..
does this relate to cooling? not sure..
but what engine has equal cooling to all cylinders??
Harley's don't and they're air cooled..

oh well..rant off...ok OT too..
-dkenny

flash7210 · **Posted:** Thu Mar 31, 2016 8:06 am

Quote:

are these problems only in the US..

Dont know. Few CRD owners from UK, EUR, or AUS report here.

Quote:

i'm sure the EGR required in the US it hurting these engines..

Still, any soot from the EGR gasses should be effecting all four cylinders equally. Not just cylinders 3 and 4.

Quote:

but what engine has equal cooling to all cylinders??

True, but for some engines its more of a problem than others.
For example, Ford V8 engines.
Its not uncommon for folks who race their Fords to add coolant paths from the rear most cylinders up to the front of the engine as a quicker route up to the thermostat outlet.
Even some Ford GT owners have done this. (you'd think that with a "supercar" such as the GT that details such as that would have been taken care of from the factory :roll:

)

And Harley engines? Aside from the many obvious differences, they have about 100 years of engineering and experience behind those engines. If there was a problem, I'm sure they have figured it out by now.

Regarding dropped valves:
So far, all the broken valves have broken at the stem. The keepers have remained intact.
The majority of broken valves have been the exhaust valve. A few reports have been the intake valve.
Valves get HOT. Especially the exhaust valves.
The only way for the valve to shed that heat is when it closes on the valve seat.
All the heat is transferred from the valve, through the seat, and to the coolant jacket.
If the valve cannot adequately transfer heat to the cooling jacket, the metal will eventually fatigue and break.

jws84_02 · **Posted:** Thu Mar 31, 2016 8:14 am

The part of effecting all cylinders from the egr isn't necessarily true either. (Or I believe anyway) that the intake and exhaust manifold and more central between 3 and 4. I could be wrong thinking this though flash

dh100m · **Posted:** Thu Mar 31, 2016 8:22 am

hi I purchased 2 used heads from uk one I used the other spare
Both had the temp sensor in hole under #3 other hole had a plug in it removed egr used this sensor rerouted outlet from head to heater inlet got rid of a lot of pluming Used the thermostat sensor hole for thermostatic sensor for electric fans seems to work lots of heat this winter
tony

flash7210 · **Posted:** Thu Mar 31, 2016 8:34 am

jws84_02 wrote:

The part of effecting all cylinders from the egr isn't necessarily true either. (Or I believe anyway) that the intake and exhaust manifold and more central between 3 and 4. I could be wrong thinking this though flash

The intake is more central to the ports of cylinders 2 and 3. Cylinders 1 and 4 are furthest away.

jws84_02 · **Posted:** Thu Mar 31, 2016 9:11 am

flash7210 wrote:

jws84_02 wrote:

The part of effecting all cylinders from the egr isn't necessarily true either. (Or I believe anyway) that the intake and exhaust manifold and more central between 3 and 4. I could be wrong thinking this though flash

The intake is more central to the ports of cylinders 2 and 3. Cylinders 1 and 4 are furthest away.

Yeah your right. It's been a little since I've been inside one. There goes that theory then.

WWDiesel · **Posted:** Thu Mar 31, 2016 12:52 pm

flash7210 wrote:

jws84_02 wrote:

The part of effecting all cylinders from the egr isn't necessarily true either. (Or I believe anyway) that the intake and exhaust manifold and more central between 3 and 4. I could be wrong thinking this though flash

The intake is more central to the ports of cylinders 2 and 3. Cylinders 1 and 4 are furthest away.

Lots of theory on all of this; depending on exactly how the exhaust soot laden gas is dumped into the intake by the flow control valve it is possible that it may all or mostly go just to one or two cylinders. Gases tend to stratify when dumped into a moving air flow stream and do not mix well unless there is some kind of turbulence induced to cause the mixing to take place. Without knowledge of the air flow characteristics of the combined FCV/intake we may never know exactly how the exhaust gas flow impact the temperatures of the individual cylinders and / or valves.
More thoughts, remember the exhaust is cooled by the EGR cooler before it is dumped into the air stream and depending on which one, incoming air or exhaust gas is cooler, certain cylinders, valves, etc.. may operate at different temperatures based on the influence of the stratified flow of exhaust gas entering the cylinders....
Now luckly with the Weeks kit installed and no FCV or EGR crap, it makes no difference, but the damage could have already took place before the mod???? :roll:

geordi · **Posted:** Thu Mar 31, 2016 2:30 pm

flash7210 wrote:

I'm brining this back to the top due to recent discoveries of dropped vales with no indication why.
So far, all reports of broken valves have been at cylinders 3 and 4.
I have never seen any reports of broken valves at cylinders 1 or 2.

Now you have. Cylinder #1 dropped two valves, both exhaust valves.

Every valve drop I have seen has been the exhaust valves unless it has also taken out one of the intake valves.

flash7210 · **Posted:** Thu Mar 31, 2016 2:59 pm

geordi wrote:

flash7210 wrote:

I'm brining this back to the top due to recent discoveries of dropped vales with no indication why.
So far, all reports of broken valves have been at cylinders 3 and 4.
I have never seen any reports of broken valves at cylinders 1 or 2.

Now you have. Cylinder #1 dropped two valves, both exhaust valves.

Every valve drop I have seen has been the exhaust valves unless it has also taken out one of the intake valves.

Good data.
Both valves huh, more food for thought.

Mountainman · **Posted:** Thu Mar 31, 2016 8:21 pm

WWDiesel wrote:

flash7210 wrote:

jws84_02 wrote:

The part of effecting all cylinders from the egr isn't necessarily true either. (Or I believe anyway) that the intake and exhaust manifold and more central between 3 and 4. I could be wrong thinking this though flash

The intake is more central to the ports of cylinders 2 and 3. Cylinders 1 and 4 are furthest away.

Lots of theory on all of this; depending on exactly how the exhaust soot laden gas is dumped into the intake by the flow control valve it is possible that it may all or mostly go just to one or two cylinders. Gases tend to stratify when dumped into a moving air flow stream and do not mix well unless there is some kind of turbulence induced to cause the mixing to take place. Without knowledge of the air flow characteristics of the combined FCV/intake we may never know exactly how the exhaust gas flow impact the temperatures of the individual cylinders and / or valves.
More thoughts, remember the exhaust is cooled by the EGR cooler before it is dumped into the air stream and depending on which one, incoming air or exhaust gas is cooler, certain cylinders, valves, etc.. may operate at different temperatures based on the influence of the stratified flow of exhaust gas entering the cylinders....
Now luckly with the Weeks kit installed and no FCV or EGR crap, it makes no difference, but the damage could have already took place before the mod???? :roll:

Yeah, where it dumps that soot is an interesting thought. And, maybe it explains why my engine which had 164k miles with active EGR (I think) has more cylinder wear in one or two of the cylinders? I guess previous owners may have used the ORM. But, I dropped all 16 rockers strait into the trash. A few were really sloppy, and the others just loose. None were even close to being keepers...

geordi · **Posted:** Thu Mar 31, 2016 11:59 pm

I will be doing some experiments with the extra valves I now have. I have two different heads that have both dumped valves. One of them is very likely the result of dealer-idiot-error, when they took a perfectly turning motor and managed to trash 3 valves in the #4 and seize the block. Based on recent experiences and observations, I am starting to wonder if my theory is wrong about how the dealership trashed the motor. (I think they used ether when it refused to start from a botched timing job) I am instead questioning if maybe the engine just chose that moment to dump the valves and that caused the damage to the others and wrecked the piston. It was tilted in the bore and smashed out the liner from the inside.

I have now personally laid wrenches on two more blocks that have dumped valves:

Naturist's block dropped a valve on the #4 exhaust at 70mph, the stem appears to have broken in the middle for reasons that are unclear - HOWEVER the stem was still attached to the spring at that point because it launched the top of the stem into the valve cover area and I found it in the adjacent stem well. Not where it should have been. The bottom of the stem / valve head found themselves in piston-land and were punished for that. The piston crown ended up tilted in the bore and quite stuck.

Another recent engine swallowed two valves on the #1 exhaust side - I suspect the rear-most valve failed first, as the stem is broken right at the weld point. The other one may have been badgered into failure by the flying shrapnel... Both are now embedded on end into the piston. There is rod damage underneath the piston but the assembly DOES rotate, surprisingly.

So I have some experiments in mind for the remaining valves. If I can find anyone who can do the testing, I would have them check the quality of the stems and heads and welds. Maybe also see if there is such a thing as more durable valves that can be swapped in. I plan to rig up a torch to blow as much heat as I can generate directly onto a valve head, while the very top tip is clamped in a vise. I want to see where any hotspots appear, if any. That should indicate where any defects may be in the metal.

If anyone else has any ideas, I'm game... I have plenty of victims for some destructive testing. I don't think I can trust them in service ever again!

Mountainman · **Posted:** Fri Apr 01, 2016 11:42 am

I am going to start checking each valve for any resistance in the guides before I slap the heads on the blocks. You think I'll be able to feel anything by pressing the valves into their seats? I know this won't help find weak spots, but at least I might be able to catch a sticky valve? maybe I'm dreaming :dizzy:

connolcj · **Posted:** Tue Apr 05, 2016 2:07 pm

This weekend I began to pull the motor of my 06 that had died on my father last fall while on an entrance ramp with light throttle. We had just finished putting it back together less than a week before the event due to multiple rocker failures. During dis-assembly we found i think another 4 rockers broken, which we new, along with 2 valves broken and embedded into the front most cylinder which I believe is cylinder 1. It also took out the corresponding piston and sleeve before wedging itself in the cylinder. I was able to break the pieces free and the rest of the rotating assembly moves freely. I have yet to fully rotate the motor until I get the rest of the remaining small pieces out of the bottom of the engine. I'll keep you guys posted with my findings and at this point this motor has become a science project/learning experience for me as I have never rebuilt an engine. I am very mechanically knowledgeable and look forward to slowly tearing it apart and rebuilding it with the exception of the price of parts with are ridiculous.

flash7210 · **Posted:** Sun Apr 10, 2016 10:09 am

Looks like there is no rhyme or reason to the dropped valves.
Could potentially happen at any cylinder. Although exhaust valves seem to be most common.

flash7210 · **Posted:** Sun Apr 10, 2016 10:15 am

Still trying to figure out if there is any correlation between dropped valves and cracked heads.
Are these just crappy parts or is there another factor.

For those who have had a cracked head, what thermostat were you using? Factory, in line, or other?

WWDiesel · **Posted:** Sun Apr 10, 2016 10:53 am

Years ago, VW engines were notorious for dropping exhaust valves and usually it was cylinder number 3 since it got less cooling flow. Occasionally I would see a dropped exhaust valve on one of the other cylinders but it was rare. Anytime we pulled an engine apart for any reason we always would replace ALL of the exhaust valves & guides with new parts or simply replace the whole head with a new complete one with all new valves....

This being said, maybe it would not be a bad idea to think about replacing all the exhaust valves on the 2.8 CRD head anytime one is removed for any service. Cheap insurance verses having to buy a whole new head and possibly piston, liner, etc...? :idea:

Thoughts...

Keeping a cool head

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