Crack in engine at the valley
04-23-2022, 08:51 PM
#46
Rennlist Member
Thread Starter
Gerrit,
Good to see that you eventually took my advice of two years ago and did the dye pen scan- sad to say my concerns were spot on about the scope of the problem. I trust you did the same on the other side of the Vee?
In your current situation and as advised earlier I would now drain down the coolant and do a pneumatic test at 15 psig to see if it holds pressure. Block the drain in the base of the vee and fill with water to see if you can spot any bubbles. Your next problem is knowing whether the cracking is limited to that face inside the vee or whether it has propagated elsewhere- remember the cylinder heads sit on the top of the cylinders and the block periphery.
I am a bit surprised that you did not go with the splint type of approach as what you have done will reduce the chances of success some but I reckon there is still a good chance you will get some life out of the motor and success depends on your definition of such. If you want a few days to get your car tested that might might qualify, if you want to run around for the next few summer months whilst you find a new block that may also qualify as a success and of course ulitimately how long it does hold up.
Quite understandable that you are going to get some negative opinions when something that folks have not had to deal with suddenly appears so do not be put off by that at this stage. As I recall you managed to buy some time previously using a $10 tube of goo gobbed on the damaged surface and it sort of worked for a while. Now you have tried something completely different and time will tell how efffective it is or is not.
From a technical perspective what folks need to understand here is that there is no "structural failure" strange as it may seem to most - there is a containment failure and that is the problem you are trying to resolve. If there was a structural problem the head gasket would have blown ages ago so what do we know? The notion that the head is going to part company with the block could not be further from reality as I am concerned. Think about it some- the strongest part of the motor is "the arch"- this holds the heads to the block and ties the motor together as one "structural monocoque"- it is immensely strong and has been known to hold motors producing 1000 BHP with no modifications. Has anything changed here?- of course not. The head bolting is embedded into the arch and is firmly holding the heads and the water jacket together with the cracked face in direct compression. If a chunck of the water jacket wall were to let go it would be another matter but nothing in the dye pen examination suggests such is imminent- the crack is obviously limited to the interface between the arch and the wall of the jacket..
If there was any structural damage to the block you would have coolant in the sump or oil in the vee not to mention a blown head gasket. The simple fact is the integrity of the head bolting system is still perfect and that is holding the heads to the block and also trying to seal the part of the block that is cracked- i.e. the heads bolts are working for you rather than against you in this instance. Despite a crack along the base of the vee all you got leaking was a few drops of coolant- that is because the bolting is trying to "seal the crack" for you but of course a leak tight seal is just not possible as things stand.
When you first noticed the failure it was not imitating a horse taking a leak- just a few accumulated drops- nothing more that caught your attention. Do you [or anyone else for that matter] see a clear and obvious reason why it should suddenly get "worse" ? So what are we trying to seal here? You have a water jacket that operates at a maximum pressure of 15 psig. The force trying to lift the Belzona off the job face is defined by F= P x A where A is the area of the "crack face" the pressure is being applied across. The crack width is "sod all" so the force trying to lift off the belzona is 15 x "sod all" which amounts to "sod all"- i.e. visually nothing [strange as it may seem] which explains why your previous dab of "gumbo" sealed it for a while. Now you are in a different ball game with Belzona 1212- I have used that stuff applied on a surface immersed under seawater to effect a pipe repair such is just how amazing that stuff really is and why it costs! .
Bottom line- just try it now - if it works all well and good- if it fails you are no worse off than you currently are. The risk is the cracks may have propagated further than you can currently see - should that prove to be the case just scrap the thing and get a new block. As I can tell you have done all that could have been done and even had you gone down the weld and repair route I suspect the total cost would be the same as or maybe greater than getting hold of a decent used block but of course even those are getting harder to find these days.
Good to see that you eventually took my advice of two years ago and did the dye pen scan- sad to say my concerns were spot on about the scope of the problem. I trust you did the same on the other side of the Vee?
In your current situation and as advised earlier I would now drain down the coolant and do a pneumatic test at 15 psig to see if it holds pressure. Block the drain in the base of the vee and fill with water to see if you can spot any bubbles. Your next problem is knowing whether the cracking is limited to that face inside the vee or whether it has propagated elsewhere- remember the cylinder heads sit on the top of the cylinders and the block periphery.
I am a bit surprised that you did not go with the splint type of approach as what you have done will reduce the chances of success some but I reckon there is still a good chance you will get some life out of the motor and success depends on your definition of such. If you want a few days to get your car tested that might might qualify, if you want to run around for the next few summer months whilst you find a new block that may also qualify as a success and of course ulitimately how long it does hold up.
Quite understandable that you are going to get some negative opinions when something that folks have not had to deal with suddenly appears so do not be put off by that at this stage. As I recall you managed to buy some time previously using a $10 tube of goo gobbed on the damaged surface and it sort of worked for a while. Now you have tried something completely different and time will tell how efffective it is or is not.
From a technical perspective what folks need to understand here is that there is no "structural failure" strange as it may seem to most - there is a containment failure and that is the problem you are trying to resolve. If there was a structural problem the head gasket would have blown ages ago so what do we know? The notion that the head is going to part company with the block could not be further from reality as I am concerned. Think about it some- the strongest part of the motor is "the arch"- this holds the heads to the block and ties the motor together as one "structural monocoque"- it is immensely strong and has been known to hold motors producing 1000 BHP with no modifications. Has anything changed here?- of course not. The head bolting is embedded into the arch and is firmly holding the heads and the water jacket together with the cracked face in direct compression. If a chunck of the water jacket wall were to let go it would be another matter but nothing in the dye pen examination suggests such is imminent- the crack is obviously limited to the interface between the arch and the wall of the jacket..
If there was any structural damage to the block you would have coolant in the sump or oil in the vee not to mention a blown head gasket. The simple fact is the integrity of the head bolting system is still perfect and that is holding the heads to the block and also trying to seal the part of the block that is cracked- i.e. the heads bolts are working for you rather than against you in this instance. Despite a crack along the base of the vee all you got leaking was a few drops of coolant- that is because the bolting is trying to "seal the crack" for you but of course a leak tight seal is just not possible as things stand.
When you first noticed the failure it was not imitating a horse taking a leak- just a few accumulated drops- nothing more that caught your attention. Do you [or anyone else for that matter] see a clear and obvious reason why it should suddenly get "worse" ? So what are we trying to seal here? You have a water jacket that operates at a maximum pressure of 15 psig. The force trying to lift the Belzona off the job face is defined by F= P x A where A is the area of the "crack face" the pressure is being applied across. The crack width is "sod all" so the force trying to lift off the belzona is 15 x "sod all" which amounts to "sod all"- i.e. visually nothing [strange as it may seem] which explains why your previous dab of "gumbo" sealed it for a while. Now you are in a different ball game with Belzona 1212- I have used that stuff applied on a surface immersed under seawater to effect a pipe repair such is just how amazing that stuff really is and why it costs! .
Bottom line- just try it now - if it works all well and good- if it fails you are no worse off than you currently are. The risk is the cracks may have propagated further than you can currently see - should that prove to be the case just scrap the thing and get a new block. As I can tell you have done all that could have been done and even had you gone down the weld and repair route I suspect the total cost would be the same as or maybe greater than getting hold of a decent used block but of course even those are getting harder to find these days.
So it is the easiest and cheapest short term solution I could do. It cannot be any worse.
And there is indeed no structural damage, there is no oil in the cooling water and vice versa.
I also checked the other side of the Vee with this dye pen and it was all good.
No idea what have caused such a crack.
I’ll keep you updated.
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merope (04-24-2022)
04-24-2022, 04:25 AM
#47
Rennlist Member
Hi Fred, you are right, I am trying to buy some time while looking for another Euro block ( M28.11, 12, 21 or 22)
So it is the easiest and cheapest short term solution I could do. It cannot be any worse.
And there is indeed no structural damage, there is no oil in the cooling water and vice versa.
I also checked the other side of the Vee with this dye pen and it was all good.
No idea what have caused such a crack.
I’ll keep you updated.
So it is the easiest and cheapest short term solution I could do. It cannot be any worse.
And there is indeed no structural damage, there is no oil in the cooling water and vice versa.
I also checked the other side of the Vee with this dye pen and it was all good.
No idea what have caused such a crack.
I’ll keep you updated.
Frost heave is the obvious candidate but not a 100% certainty I would say. At least you now know the other side is superficially clear of cracks albeit one might expect something similar to happen both sides all things being equal.
Do not be "surprised" if the "repair" seals off the leak and does so for as long as you want or need it to- for sure nothing lost and plenty to be gained here but realistically speaking your motor [sadly] is toast.
Any idea how thick the Belzona layer was covering the root of the crack?
04-24-2022, 11:54 AM
#48
Rennlist Member
Well Gerrit, to add a little bit of levity to a bad situation, at least you are getting closer to having a 944 block. Once that side breaks off, you are there.
04-24-2022, 04:43 PM
#49
Rennlist Member
Thread Starter
Gerrit,
Frost heave is the obvious candidate but not a 100% certainty I would say. At least you now know the other side is superficially clear of cracks albeit one might expect something similar to happen both sides all things being equal.
Do not be "surprised" if the "repair" seals off the leak and does so for as long as you want or need it to- for sure nothing lost and plenty to be gained here but realistically speaking your motor [sadly] is toast.
Any idea how thick the Belzona layer was covering the root of the crack?
Frost heave is the obvious candidate but not a 100% certainty I would say. At least you now know the other side is superficially clear of cracks albeit one might expect something similar to happen both sides all things being equal.
Do not be "surprised" if the "repair" seals off the leak and does so for as long as you want or need it to- for sure nothing lost and plenty to be gained here but realistically speaking your motor [sadly] is toast.
Any idea how thick the Belzona layer was covering the root of the crack?
I used 2 layers of Belzona, each about 2mm thick
And between both layers I put a thin layer of aluminium foil.
04-25-2022, 11:12 AM
#50
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Join Date: Aug 2014
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For those with time on their hands, I propose this experiment:
Get some aluminium plates. Mill out the plates so when two plates are bolted together there is a cavity between them. Add a fitting to pressurize the cavity. Before bolting the two plates together with the gasket sealant of your choice, simulate a crack by filing off a bit of the plate at an edge, opening the cavity to the outside. How much? Aim for "cracks" that leak about the same as you are experiencing. But it could be a variable, among many others if you are feeling ambitious. You could put four different simulated cracks on the four sides of your test article.
The principle variable, of course, is the suite of repair methods and/or variations you want to evaluate. The most arduous part of the experiment is to apply many simulated engine cycles. I think we all expect an initial thrill of victory, followed by a later agony of defeat. To be more positive, however, let's define "defeat" to mean only a seriously inconvenient leak, not any leak.
Extra credit for simulating a crack-opening displacement, as may occur during engine operation. Perhaps a strategically located, fine-threaded bolt that forces the crack open.
Get some aluminium plates. Mill out the plates so when two plates are bolted together there is a cavity between them. Add a fitting to pressurize the cavity. Before bolting the two plates together with the gasket sealant of your choice, simulate a crack by filing off a bit of the plate at an edge, opening the cavity to the outside. How much? Aim for "cracks" that leak about the same as you are experiencing. But it could be a variable, among many others if you are feeling ambitious. You could put four different simulated cracks on the four sides of your test article.
The principle variable, of course, is the suite of repair methods and/or variations you want to evaluate. The most arduous part of the experiment is to apply many simulated engine cycles. I think we all expect an initial thrill of victory, followed by a later agony of defeat. To be more positive, however, let's define "defeat" to mean only a seriously inconvenient leak, not any leak.
Extra credit for simulating a crack-opening displacement, as may occur during engine operation. Perhaps a strategically located, fine-threaded bolt that forces the crack open.
04-27-2022, 07:43 AM
#51
Rennlist Member
Probably about as much as you can reasonably do.
Did you implement the pneumatic leak test I suggested?
04-28-2022, 09:47 AM
#52
Burning Brakes
this was my 944 block that didnt respond well to an easyout - never going there again
Last edited by C531XHO; 04-28-2022 at 09:49 AM.
04-29-2022, 01:51 AM
#53
Addict
Rennlist Member
Rennlist Member
04-29-2022, 03:16 AM
#54
Burning Brakes
No, i considered welding but that would have been engine out, full strip down etc. I tried drilling and tapping it in place with jb weld unsuccessfully. What shocked me was how easily the material split in the first place. My mistake. Where i have had problems with broken fixing on either of my 2 928s since, i have gone down the cobalt drill/insert route. Worked well on CPS attachment for example.
OK so thread hijack over, I hope the OP manages to find a tolerable fix
OK so thread hijack over, I hope the OP manages to find a tolerable fix
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RennHarry (04-29-2022)
04-29-2022, 05:57 PM
#55
Rennlist Member
Thread Starter
04-30-2022, 01:34 AM
#56
Three Wheelin'
That is indeed true, but when you don’t go to the mandatory MOT every 2 years, you will probably get a huge fine, depending on how many months your are overdue with your MOT. I thought that in the past you could get a special extension p.e. when your car is being restored…but I could not find this in the legislation.
I went with cars a year , 2 years overdue.
Tip : if you go in the same year of the past period , they don't change the dates .... so if 11 months overdue , you get a valid period of 1 month !
I had a BMW , more the a year overdue , and i got a new "date" , so valid for a year again.
04-30-2022, 01:39 AM
#57
Rennlist Member
04-30-2022, 01:48 AM
#58
Three Wheelin'
A M28/21.... ② Porsche 928 motor 4.7 injectie — Motor en Toebehoren — 2dehands
there was another one for sale , must look if it sold.
PS no personal knowlegde of condition....
there was another one for sale , must look if it sold.
PS no personal knowlegde of condition....
05-13-2022, 06:06 PM
#60
Rennlist Member
Thread Starter
A M28/21.... ② Porsche 928 motor 4.7 injectie — Motor en Toebehoren — 2dehands
there was another one for sale , must look if it sold.
PS no personal knowlegde of condition....
there was another one for sale , must look if it sold.
PS no personal knowlegde of condition....
Important to me for such a used engine is that compression of each cilinder is good.
In the meantime I had a chat with another very friendly and skilled guy from Garage De Loods in the Netherlands : he told me no to weld the huge crack in my engine. it will be very hard to weld and eventually you'll end up with the same issue...
Better would be to find a good shortblock (with minor damage to the cilinders) and put steel sleeves. Apparently he works with someone who has over 25 years of experiences with putting sleeves in aluminium engines.
The advantage (compared to new alusil coat and oversize pistons) is that you can reuse your pistons, and that it is cheaper ...and you can also replace the sleeves when they are worn.