Coolant leaking from exhaust manifold blt on Perkins 4108

[Warby12]

Hi,
We were having a perfect day until we noticed coolant coming out of the very aft exhaust manifold bolt on our Perkins 4108

It has a Bowman heat exchanger on it. Of the four manifold bolts the back two are both loose, coolant leaking out of the very aft one. When i put a spanner on it and turn a quarter turn, it turns back again like its rubber.

Looks like stripped thread or something but why the coolant? Do the manifold bolts go throught the water jacket?

Motoring slowly back to port now, fortunately nice calm day but what could this be? If there is no bolt through water jacket setup, is it a cracked head?

Thanks for any help

[MarkSF]

I'm not an expert on the Perkins, but it is not unusual for exhaust manifold bolts to thread into coolant passageways. Your solution might be as simple as finding the right thread sealant, and reinstalling the bolts.

This happened to me on my Triumph TR8. I just tightened the bolts. No more leak.

[Warby12]

Hi Mark, thanks for your thoughts and I hope you are right but my searching is not turning up any evidence yet.

[Captsteve53]

The Perkins studs holding the heat exchanger to the head have a bit of a known issue of working loose and destroying the threads, many over the years have been heli coiled and when doing this they drill through into the water gallery in the head as not to much material at that point,

No problem doing this as a repair but would personally put thread locker/sealant on the studs at the time, some one may have done this repair previously?

Cheers Steve

[Argyle38]

Watching this thread since I have been fighting the exact same problem for several years. Thinking about getting a mechanic/welder involved for a proper fix, whatever it takes.

I've had my manifold off three times over the past several years trying to fix the leak. The first time it actually separated from the block, so I didn't remove it that time, it kind of removed itself. I had one broken stud on both the forward and aft connections points. When the second stud broke from the aft connections, coolant mist and exhaust filled the engine room. So this tells me there was already a coolant leak through the stud threads. So I drilled out and re-tapped the broken studs, replaced the gaskets and used 'Mercury Perfect Seal' on both the threads and the gasket. This product was recommended by the manager of my Marina. Didn't work. I had a leak and overheated the engine (turned it off in time so no damage) the following season.

Removed the manifold again the next year. The threads on two of the four studs were badly corroded, so I tapped in the next size up (from 5/16" to 3/8") hoping that cleaner threads might seal better. Also, the gasket seat on the engine block side has corrosion pits as well. I cleaned up the area and filled the pits with JB Weld steel stick then fared down to a smooth flat surface, hoping this would allow the gaskets to work properly. This lasted about two years of light use, but failed last year during a long trip with a lot of motoring. The forward connections point seems to be holding, but the aft one is leaking again.

So that's where I am now. I'm considering all options and will start talking to local mechanics later this month, unless something else I can try presents itself in this thread. What I'm thinking about doing is having a welder come in and fill in the corrosion pits and possibly the bolt holes as well, then fairing down what should then be clean metal and of course re-tapping the bolt holes. Another thing I'm considering for the bolt holes would be key inserts welded in, if I can find a key insert with a bottom, so the completed design would be water tight.

Not trying to de-rail your thread with my woes, but figure I'd post what I did. Whatever the proper fix for this issue is, the above isn't it.

[Warby12]

Thanks everyone, looks like stripped threads on something for sure from what you are saying. At least we know what we are up against, I guess

I will take the manifold off this morning and check it out. I have thread taps on board. Must admit I have never used one in metal before.

[IslandHopper]

If it is stripped threads I would highly recommend fitting Helicoils...

[Mistress Sirena]

Some should look at the riser or exhaust piping putting excessive load on manifold.

[Lepke]

The problem with drilling and taping to a bigger size is some stud holes are very close to the water jacket. With helicoil or similar, you're only removing enough material to thread in the new threads. helicoil is a looks like a spring so the tap is a thread to fit the outside. Usually a drill isn't needed. Other brands have a stainless insert with the original threads on the inside.
Where it's close to the water jacket or is leaking, I get it dry and use a sealer. I've probably done a hundred thread inserts. It should be a no brainer.

[jamhass]

Originally Posted by Argyle38

What I'm thinking about doing is having a welder come in and fill in the corrosion pits and possibly the bolt holes as well, then fairing down what should then be clean metal and of course re-tapping the bolt holes.

One needs to be very careful welding cast iron. It does not usually weld well, and can easily crack from the heat. Brazing might be more successful. Make sure your welder is experienced with cast iron.

[Argyle38]

Originally Posted by jamhass

One needs to be very careful welding cast iron. It does not usually weld well, and can easily crack from the heat. Brazing might be more successful. Make sure your welder is experienced with cast iron.

Thanks for the heads up on that. Is the engine block of a 4108 cast iron or steel?

Either way, I definitely want a welder who is experienced in this exact thing. Kind of like seeking out a surgeon who is experienced with a surgery that you need done.

[Argyle38]

Originally Posted by Lepke

Where it's close to the water jacket or is leaking, I get it dry and use a sealer. I've probably done a hundred thread inserts. It should be a no brainer.

What kind of sealer do you use that can withstand the temperatures, pressures and vibration for this application?

[Captsteve53]

Perkins blocks/heads are cast Iron, and therefore welding/brazing etc is to be considered a NO NO as it can easily lead to stress cracking unless completed under controlled work shop conditions,

Using the Heli Coil system would be your best bet, then lock into place with a high temp thread-locker /sealant such as High Temp Loctite 266

LOCTITE® 266™ Threadlocker High Temperature/High Strength - Henkel

Have never seen this repair fail when using Loctite 266 following the directions

Cheers Steve

[Warby12]

Well after all this..... It looks like it had simply shaken itself loose!!

All the bolts came out with good threads, except the fwd one which looks like it has had a helicoil repair, (not that I would know a helicoil repair from a slinky).
All of the holes go straight through to the water jacket so maybe they have been drilled out previously?

Also, the Bowman heat exchanger comes with two threaded holes on the back towards the engine and I had put two brackets into them to help support the thing. They connect the heat exchanger to top of the head. i thought that was a good idea although I haven't seen any info to support it.

I think what has happened is, the aft two bolts have shaken loose and after a while the bracket I added snapped, leading to a sudden increase in coolant and fumes in the boat, always a scary moment.

Tomorrow I will check the bolts can be torqued up and if so This Time fit it with some proper thread sealant! Aaaaaannnd check it regularly

Anyway it looks like a new engine and the resultant poverty have been avoided for at least three days.

By the way, plan B had looked like tap to larger size or helicoil which would have been good skills to acquire, maybe some other day.

Thanks everybody for your help, it is very very much appreciated!!!

[Argyle38]

Cool! Let us know how it holds up.