Perkins T6.354 with Blow By

[Hal Landvoigt]

Lurker trying to become new boat owner here. I will allow this message to suffice as an introduction but I have been shopping for a boat for a little over a year now and been reading as much as possible about what I'm gettign myself into. I recently put an offer in on a Roughwater 35 with a Perkins T6.354 engine. I had a survey scheduled for two weeks from now and just got a call from the owner that on a very recent outing the boat started to blow-by. He wants to push out the survey until he can have his mechanic come look at the issue. I'm trying to assess how major of an issue this might be. Here is what I can can tell you about this boat:

Engine has just under 1600 hours. When the PO purchased the boat in 2018 it had right around 1430 hours, so less than 200 hours in 6 years. At that time he had an engine survey done and the overall results of that were that the engine was in good operating condition and that it should be reliable. Since then he has been meticulous about the maintenance and has changed the oil at least twice with Rotella T4 15-40 and had the injectors cleaned. Sometime back in 2023 he had some issues with blowby and at that time cleaned the injectors and the cylinders checked with a borescope. Overall things looked good except some carbon fouling in #2 valves and he was advised that he needed to be running the engine harder than he was to help burn off carbon deposits.

On paper this engine should be good for at least another couple thousand hours but this blow by issue gives me pause. I have read pretty much everythign posted on TF and elsewhere that I could find about blowby on these engines. My gut tells me this could be as simple as a clogged breather screen or stuck rings and that the solution could work itself out with some seafoam and more regular use. Conversely, if the engine is just a very large paperweight at this point the costs to repower would not be something that I want to take on.

Here are links to videos of the engine startng and of the exhaust at startup. T6.354.

At this point I'm waiting for the owner to have his mechanic come out and look at the engine and then we will see where we go from here. I'm just looking for any insights people might have about these engines and this particular condition.

Thanks for the advice,

Hal

 

[jleonard]

Those engines smoke at startup. Once the coolant temperature reaches 140 F it should clear up. I had an old Mainship that had one, and knew many other owners who had that engine. They all smoked at start up then cleared up.
I didnt see anything unusual in your video.

 

[Hal Landvoigt]

That is my observation, once we ran it for a bit it really cleared up a lot and he said it has started the previous day with less smoke.
I have enough experience with old car engines to know that sitting is one of the worst things for an engine and it makes sense to me that the low hours over the past few years and the owners comments about babying the engine all point to carbonized rings as a very likely cause of blow-by.

Hal

 

[Barking Sands]

I don't know. That's quite a bit of smoke. Starting it the previous day with "less" smoke isn't helpful..lol. Why does he think he has blow by? With all the details so far, including the valve details, a leak down test is in order. Not just a compression test...but leak down test as well. That will determine if you have low compression and where its going. Is it a ring issue with blow by into the crank case that also allows excessive oil in combustion chamber (pull the oil cap and check for chugging)? Is it a valve sealing issue on the exhaust valves? Is it a head gasket issue etc? Leak down will tell the tale. IMO that engine will require some level of Mx soon. It could be mild like valve seals or it could be complete overhaul. Good thing is Perkins is somewhat cheap to overhaul.

If its a turbo model could be turbo issues as well.

 

[Hal Landvoigt]

I don't know. That's quite a bit of smoke. Starting it the previous day with "less" smoke isn't helpful..lol. Why does he think he has blow by? With all the details so far, including the valve details, a leak down test is in order. Not just a compression test...but leak down test as well. That will determine if you have low compression and where its going. Is it a ring issue with blow by into the crank case that also allows excessive oil in combustion chamber (pull the oil cap and check for chugging)? Is it a valve sealing issue on the exhaust valves? Is it a head gasket issue etc? Leak down will tell the tale. IMO that engine will require some level of Mx soon. It could be mild like valve seals or it could be complete overhaul. Good thing is Perkins is somewhat cheap to overhaul.

If its a turbo model could be turbo issues as well.

Thanks for this advice. I'm going to try to find an engine surveyor in the area and try to make the best initial assessment as is possible. Having the previous survey from 6 years ago I can see what was and wasn't done to most of the boat pretty easily. Engine internals require a bit more diagnostic process but I'd rather pay a penny upfront to know how many pounds I'll be shelling out in the future.

H

 

[Hal Landvoigt]

Here are a few updates on this, based on new information I got from the owner. He had his mechanic out to look at the engine and the mechanic seems to think that the blow by is entirely caused by the excessive carbon build up on Cylinder #2. It turns out that the owner in doing some annual maintenance this year determined that the injector on Cyl #2 was the incorrect injector (and he has no knowledge of how long that injector has been in place). Additionally, it seems that the only place where the blowby was evident was in coming out of the oil filler cap and from under the valve cover seal. There was no oil pushing out the dipstick fill tube, etc.

They are talking about pulling the head to clean up the carbon on #2 valves. I'm inclined to have the mechanic also perform a leak down test on all 6 cylinders and test Cyl #2 before and after the valve cleaning. I think that would give me a bit more assurance as to the condition of the engine.

H

 

[Barking Sands]

Here are a few updates on this, based on new information I got from the owner. He had his mechanic out to look at the engine and the mechanic seems to think that the blow by is entirely caused by the excessive carbon build up on Cylinder #2. It turns out that the owner in doing some annual maintenance this year determined that the injector on Cyl #2 was the incorrect injector (and he has no knowledge of how long that injector has been in place). Additionally, it seems that the only place where the blowby was evident was in coming out of the oil filler cap and from under the valve cover seal. There was no oil pushing out the dipstick fill tube, etc.

They are talking about pulling the head to clean up the carbon on #2 valves. I'm inclined to have the mechanic also perform a leak down test on all 6 cylinders and test Cyl #2 before and after the valve cleaning. I think that would give me a bit more assurance as to the condition of the engine.

H

Blowby from the oil filler cap and the valve cover seal points away from any valve issue and to either a head gasket issue or a piston ring issue. In reality the oil filler cap, valve cover cavity and oil dipstick all lead to the same chamber. Not sure why no chugging came from the dipstick. The narrow passage may mask it if the blow by is mild or maybe the oil cap was already off relieving pressure? If the exhaust valve was not sealing...when you do a leak down test...you will hear air coming out of the exhaust port predominately. Really the exhaust manifold should be removed during leak down if the exhaust valve sealing is heard or suspected. If and when the cylinder head comes off use water or alcohol to pour into the exhaust port with the port facing up to fill the port. See if fluid leaks past the valve into the combustion chamber area. Do this right when you pull off the head and no cleaning. In addition, look into the cylinder walls for scoring. If you do a leak down and pull off the cylinder head..you guys will discover the issue I am sure. Good luck! Hopefully the owner is agreeable to fix or adjust price as needed. Sounds like he is taking the right steps. Just dont sugar coat it or allow anyone in the group to sugar coat it. I know when I used to build my own expensive race motors..I sugar coated a couple of my very own issues all for my own perceived benefit..lol. It never worked out...lol.

 

[Hal Landvoigt]

Blowby from the oil filler cap and the valve cover seal points away from any valve issue and to either a head gasket issue or a piston ring issue. In reality the oil filler cap, valve cover cavity and oil dipstick all lead to the same chamber. Not sure why no chugging came from the dipstick. The narrow passage may mask it if the blow by is mild or maybe the oil cap was already off relieving pressure? If the exhaust valve was not sealing...when you do a leak down test...you will hear air coming out of the exhaust port predominately. Really the exhaust manifold should be removed during leak down if the exhaust valve sealing is heard or suspected. If and when the cylinder head comes off use water or alcohol to pour into the exhaust port with the port facing up to fill the port. See if fluid leaks past the valve into the combustion chamber area. Do this right when you pull off the head and no cleaning. In addition, look into the cylinder walls for scoring. If you do a leak down and pull off the cylinder head..you guys will discover the issue I am sure. Good luck! Hopefully the owner is agreeable to fix or adjust price as needed. Sounds like he is taking the right steps. Just dont sugar coat it or allow anyone in the group to sugar coat it. I know when I used to build my own expensive race motors..I sugar coated a couple of my very own issues all for my own perceived benefit..lol. It never worked out...lol.

I follow that unless the issue is that the valves aren't opening and then wouldn't it push past the seals and pressurize under the valve cover? Editing this as that doesn't make sense either. If they end up pulling the head I'm going to try to go up and get a look at the cylinder walls, etc. Scoring or glazing would likely indicate a ring issue.

I know what your're saying about using alcohol to test if the valves seal.

H

 

[Barking Sands]

I follow that unless the issue is that the valves aren't opening and then wouldn't it push past the seals and pressurize under the valve cover? Editing this as that doesn't make sense either. If they end up pulling the head I'm going to try to go up and get a look at the cylinder walls, etc. Scoring or glazing would likely indicate a ring issue.

I know what your're saying about using alcohol to test if the valves seal.

H

There is valve seals and then there is valve sealing. Two different things.

Valve seals are the little pressed on Viton seals that go under the valve springs/retainers on the valve stem and control oil as the valve moves up and down inside the valve guides. Bad valve seals are usually responsible for oil smoke on start up that quickly dissipates.

Valve sealing is when the valve mates with the valve seat when closed and it is this sealing that is responsible for proper compression (along with rings). If they mentioned carbon build up due to incorrect or poor injector performance they are likely talking about valve seat sealing resulting in poor compression or blow by. But poor compression due to intake or exhaust valve sealing will result in air moving from inside the cylinder past the valve seat and into the associated intake or exhaust port. But again this will not result in huffing out of the oil cap or valve cover gasket.

The order of troubleshooting would be to do a proper leak down test. This takes time to set up. And may require some disassembly to properly determine where the air is going. Sometimes you hear the air escaping but its hard to know where. Other times its very obvious. If blow by is determined to be exiting into the crankcase you will really need to pull the head off. If its a gasket it should be obvious. With any luck it just needs a new head gasket. Not a horrible job for any decent diesel mechanic. And he can set the valves on the way back together.

A borescope into the injector hole may tell the tale as well.

Fingers crossed. But dont take the boat unless the motor is fully repaired or the cost of repair is fully estimated from a reputable shop and factored into the price...plus a small margin. Better to buy after repairs are done and some hours have been put on it.

 

[Hal Landvoigt]

I follow all of what you are saying and I do understand the difference between the seals and the valve seat sealing. I was able to speak with the person who did the original engine survey 6 years ago. He's now a retired mechanic but one very familiar with Perkins engines and he gave me a bit of advise. On suggestion he had which would help indicate if the rings are not seated (or worse if a piston is holed) is to crack the fuel line on each injector and see if there is a change in the engine's running. WIth good compression and properly seated rings and valves I should notice a difference in the smoothness of the idle. If there is no change then that would indicate that cylinder is not getting good compression.

The flip side of this is I also spoke to the mechanic who is currently maintaining this engine and they don't sound super familiar with Perkins diesel engines. Its possible this is the only Perkins engine they're servicing or have ever serviced. I inquired about having them do an engine survey but they will only offer a non-invasive survey and they will not disassemble any part of the engine in the process. I don't think thats going to tell me much and that may even rule out a leak down test based on the comments I got from them.

The challenge is that the boat is 11 hours away (by water) from my home port and 4 hours from the next nearest port. Thats a long way to take a boat to find out its shot. Obviously some heavy questions for me to consider. I'm meeting with my general surveyor on Thursday and I'll discuss all of this in more detail with her and try to come up with a course of action. It may be that I try to bring someone up to the boat with me (its only 2 hours in a car) even if I have to pay for their travel time. I'd rather pay a bit extra to get a good set of answers from a mechanic deeply familar with these engines then to get inconclusive answers and find I've bought an anchor.

Thanks for the solid advise. If not this boat, its possible there is another boat out there in the world for me to buy.

Hal

 

[kapnd]

Too much oil in the sump can cause blowby symptoms, and an be further aggravated by engines angle as installed.
Follow the manufacturer recommended amount of oil, do not rely on the dipstick for true oil capacity measurements.

 

[Hal Landvoigt]

I had this thought too. Pretty sure the owner is just putting in 8 quarts at each change as he mentioned the dipstick is unrelable. That raises the question of knowing whether you are empting the oilpan or how empty you are getting it using an oil sucker. If I can only get out 7 quarts (as and example) and the specs call for 8 quarts, do I add 8 quarts or only 7 quarts and assume there is still 1 quart in the engine?

 

[kapnd]

An overfilled sump will slowly push out excess oil, and stabilize when it’s found its happy place.
Once you find the sweet spot, scratch a new mark on the dipstick .
There’s a generous safety margin built in, so it won’t ruin your motor if it gets a couple of quarts low.

 

[Irish Rambler]

Those engines smoke at startup. Once the coolant temperature reaches 140 F it should clear up. I had an old Mainship that had one, and knew many other owners who had that engine. They all smoked at start up then cleared up.
I didnt see anything unusual in your video.

Those Perkins are near bullet proof. All those older diesels smoke on startup. Many of those older turbo engines, if they've been sitting around or tootling along at slow speed, they need to be got up to working temperature and then given 20 minutes at WOT to get all the old soot deposits blown out. You can reduce the smoke by filling with 25% which will let the engine run a tad warmer and cleaner. If you feel you have to run the engine in the marina, securely fasten your mooring lines, engage it in gear and gently increase the revs to around 1000 rpm so its under a light load which will help it to reach operating temperature quicker and burn cleaner.

 

[KnotYet]

I note that you are in the Seattle area. Perkins engines are not at all rare and there
are several well known service centers in that area. Knowledge and parts abound.

The business of the one incorrect injector merits looking into on such a low hour unit.

 

[Hal Landvoigt]

I am planning to go back up to see the boat thsi week. The owner has bought a compression tester and we are going to check cylinder compression, clean the injectors, replace the fuel filter and racor filter, and see where we get. In talking to him the pressure coming out of the oil filler cap was not enough to blast the cap into the air. The other thing he mentioned was that on this past outing where he experinced what he called "blowby" he was also not able to get the engine to rev up to max rpm. I'm hopeful (as is the seller) that these issues are minor, may be even just dirty fuel and some clogging. If we can get it to a state where I feel confident in bringing it back to Seattle the 10+ hour trip should let us really blow it out. I may dump a little seafoam into each cylinder and let it sit overnight.

Can anyone recommend a good diesel fuel additive/polisher that can address solids and H2O in the fuel? Something prophylactic?

Hal

 

[KnotYet]

I am planning to go back up to see the boat thsi week. The owner has bought a compression tester and we are going to check cylinder compression, clean the injectors, replace the fuel filter and racor filter, and see where we get. In talking to him the pressure coming out of the oil filler cap was not enough to blast the cap into the air. The other thing he mentioned was that on this past outing where he experinced what he called "blowby" he was also not able to get the engine to rev up to max rpm. I'm hopeful (as is the seller) that these issues are minor, may be even just dirty fuel and some clogging. If we can get it to a state where I feel confident in bringing it back to Seattle the 10+ hour trip should let us really blow it out. I may dump a little seafoam into each cylinder and let it sit overnight.

Can anyone recommend a good diesel fuel additive/polisher that can address solids and H2O in the fuel? Something prophylactic?

Hal

It takes some mechanical know-how to get the most from a compression test.
Hopefully there will be someone with the know-how as well as a good gauge.
If the boat has sat little used for six years, as you hinted, there could be some
fouling from water in the fuel tank(s). Inspecting this would be part of a survey.
Wait for that result and take it from there.

 

[kapnd]

A leak down test would be much more informative than a compression test, but I’d want to get the fuel system up to par, including clean fuel first.
Additives just might bring more problems to the table.
Alcohol, almost always a major ingredient, does not remove water, but allows it to pass through the system.
Your fuel pump and injectors are not designed to pass water, no matter how small the particles, and damage can occur, though It may not show immediately,
If the fuel tanks are contaminated, the only real solution is to get them cleaned, and the fuel polished.
Multiple stage fuel filtration can be a very effective tool, some great reading on the subject available at sbmar.com under “Tony’s Tips”.
I would not run an old motor (any motor!) at WOT for extended time, 10-20 minutes should be sufficient to clear the exhaust side and allow you to note speed, rpm, and temps, as well as packing temp, prop/rudder vibration, shaft run out, etc.
I would suggest doing that during sea trial, before you finalize the purchase.

 

[Hal Landvoigt]

Thanks everyone for all the information, tips, advice, etc. This is a learning process that I don't think will ever end. I spent the day up with the owner yesterday lookign at the boat in more detail. We pulled all the injectors and used a borescope to look inside the cylinders and at the valves. Granted my experience is with gas car and scooter engines, but to me the cylinders looked pristine. Crosshatched honing marks were clearly visible, valves looked clean and largely free of carbon, the tops of the pistons were bright and shiny. The one thing we did notice was oil dripping from the top of the cylinders -- a sign of leaky valve seals -- which I could expect for a 49 year old engine.

At the advice of my surveyor I contacted a diesel mechanic who she recommended for some unbiased advice. His comments were that any engine of this age is going to exhibit a degree of blowby, but that if it starts easily and performs well, that blowby is not the end of the world.

One other thing that I noticed is that the owner had inserted a small "puke" filter (canister oil type filter) on the vent hose that runs between the valve cover and the turbo. To my eye the filter is far too small (less than 1/2 the size of a coke can) and if this is filter is saturated with oil then that is certainly going to create backpressure out of the valve cover that has to go somewhere. I think a true puke bottle that allows the blown off oil to be collected but still returns gasses from within the valve cover to the turbo would be more appropriate, especially based on what I've read hear about Perkins' and puke bottles.

The owner is going to put some seafoam into the cylinders and let them soak a few days and then we'll see if this improves things at all.

Part of me feels like none of these issues are true deal killers, but rather points to be negoitiated in the purchase. This is an old boat. It has things that need to be fixed or maintained, but a lot of the systems on the boat have been upgraded quite recently (electrical, nav, paint, heat exchanger, batteries) and he has been on top of the maintenance even if the usage has been low. Any boat is going to have issues, but I feel like I have a very reasonable and honest seller who wants to work with me to make this deal work.

Hal

 

[PhilPB]

I have the same engine and have never experienced smoke like that or any at all, but I take mine out weekly and the po did as well until he became ill and couldn't use it. After all is said and done, it's an old motor and probably not terrible. I'm also old and not too terrible, depending on who you ask.