KAD32 – Coolant Leak at Exhaust Manifold Gasket

[dr_oli]

Hi,

I'm currently experiencing a coolant leak on my KAD32, which I traced to the gaskets between the exhaust manifold and the engine block. I (my mechanic) replaced the gaskets with new ones, but unfortunately, there's still a small leak — although reduced. During both pressure testing and operation, I'm still losing about 200 ml of coolant per hour.

I'm considering replacing the gaskets again (this time myself) and would like to ask:

1. Are there official torque specifications for the exhaust manifold bolts?
2. Should I apply any sealant to the gaskets during installation?

On a side note, during the last pressure test, the system held pressure for an hour without any noticeable drop, but I plan to extend the test to be sure.

Thanks in advance for your help!

Best regards,
Oliver

 

[dr_oli]

Only specs that I found were related to:

Turbocharger, exhaust pipe flange ...................................... 45 Nm (33.1 lbf-ft)

But nothing for anything else so I suppose that general recommendation applies:

Dimension Tightening Torques
Nm lbt.ft
M5 6 4.4
M6 10 7.4
M8 25 18.4
M10 50 36.9
M12 80 59.0
M14 140 103.3

right?

I'll check when I go to boat but is this M10 on KAD32?

 

[dr_oli]

I just got back and checked — the bolts are M10, so the correct torque should be 50 Nm.

Here's the situation:

The first time the mechanic worked on the boat, I went for a test drive and noticed a coolant loss of about 200 ml. I called him back, and he found that two bolts could be tightened by hand — meaning the initial installation was poorly done. He then tightened the bolts (the ones he could access) to 50 Nm, but the coolant leak persisted.

Today, I removed the supercharger and air filter to access 7 out of 8 bolts. I confirmed they were all torqued to 50 Nm. Still leaking. I then loosened them and re-torqued gradually in steps — 30, 40, and finally 50 Nm — using a diagonal pattern to ensure even pressure. No improvement. I even tried lowering the final torque slightly to 41 Nm — still leaking.

Do you think the gaskets could now be damaged due to:

- the initial poor tightening (including running the engine for an hour),
- and the repeated torque changes?

I'm planning to call another mechanic, but this time I want to make sure he:

- checks that both surfaces (exhaust manifold and engine block) are perfectly flat — especially since the exhaust manifold is brand new,
and only proceeds with reassembly using new gaskets if the surfaces are confirmed flat.

Do you have any tips or recommendations for this situation?

Thanks in advance!

 

[kashurst]

If you can, do it yourself. It's not that hard and you will know it has been done properly.

Once the bolts have been slackened on a gasketed joint, you are on a hiding to nothing trying to create a good seal by messing about with torque settings. Once they have been loosened they don't spring back to their original state. Best case you might get lucky, worst case if you overtighten the bolts/studs you or a ham fisted mechanic will bend or worse, crack something expensive.

Hopefully it is just leaky gaskets as you describe, but if you get it all to bits you can have a proper look at the exhaust manifold for any signs of cracks etc. The mechanic who recently replaced the leaking gasket - did he replace all of them? or just the one that was leaking? As to finding some bolts that could be tightened by hand - seriously? Don't let him back on board.
Then properly clean all the mating surfaces properly with file/emery/flat scraper. Then put it all back together with all new volvo gaskest to the correct torque, no extra sealant should be needed especially on the exhaust manifold.
As you tighten it all back in the correct sequence (check manual - dont just start at one end. If you haven't got one ask on here) the new gaskets will squish and seal as the bolts etc hit the correct torque.

There are very very few so called boat mechanics I would let near my lawn mower, let alone an expensive boat engine.

 

[volvopaul]

I always apply sealant to the area where the water passes , I’ve never had one leak other than when the manifold had warped due to a serious overheat as I was doing this as part of a head gasket replacement, I ended up having the manifold surface ground as in the same principle per cylinder head , that cured the leak .

 

[dr_oli]

If you can, do it yourself. It's not that hard and you will know it has been done properly.

Once the bolts have been slackened on a gasketed joint, you are on a hiding to nothing trying to create a good seal by messing about with torque settings. Once they have been loosened they don't spring back to their original state. Best case you might get lucky, worst case if you overtighten the bolts/studs you or a ham fisted mechanic will bend or worse, crack something expensive.

Hopefully it is just leaky gaskets as you describe, but if you get it all to bits you can have a proper look at the exhaust manifold for any signs of cracks etc. The mechanic who recently replaced the leaking gasket - did he replace all of them? or just the one that was leaking? As to finding some bolts that could be tightened by hand - seriously? Don't let him back on board.
Then properly clean all the mating surfaces properly with file/emery/flat scraper. Then put it all back together with all new volvo gaskest to the correct torque, no extra sealant should be needed especially on the exhaust manifold.
As you tighten it all back in the correct sequence (check manual - dont just start at one end. If you haven't got one ask on here) the new gaskets will squish and seal as the bolts etc hit the correct torque.

There are very very few so called boat mechanics I would let near my lawn mower, let alone an expensive boat engine.

All gaskets were replaced.
I cannot find any instructions for bolts/studs in this area neither anything about sequence. Any tip?

Most likely I'll do that alone (I am not afraid of work and like you said I'll know what is and how done; I might be slow but, at least, I am very precise ).

 

[dr_oli]

I always apply sealant to the area where the water passes , I’ve never had one leak other than when the manifold had warped due to a serious overheat as I was doing this as part of a head gasket replacement, I ended up having the manifold surface ground as in the same principle per cylinder head , that cured the leak .

Do you have any recommendations for high-temperature sealants? I'd prefer to avoid using one, as it's not officially recommended for this type of joint — but I'd like to be prepared just in case.

Also, how do you check if a surface is properly ground/flat?
Sorry if these are naive questions — I’ve never done this before, but since it’s becoming harder to find a good mechanic, I’ve started doing more and more myself.

Also, do you know torque specs and sequence?

 

[dr_oli]

Btw. thanks to both

 

[Mr Googler]

https://www.dropbox.com/scl/fo/j7n6...ey=a84z41g1ddkapjynpkmuqt3ob&st=il03iq7w&dl=0

All manuals are here

If you have tightened them and still leaking, the only answer is to start again and use sealant. I’d you high temp rtv sealant

 

[dr_oli]

I always apply sealant to the area where the water passes , I’ve never had one leak other than when the manifold had warped due to a serious overheat as I was doing this as part of a head gasket replacement, I ended up having the manifold surface ground as in the same principle per cylinder head , that cured the leak .

https://www.dropbox.com/scl/fo/j7n6...ey=a84z41g1ddkapjynpkmuqt3ob&st=il03iq7w&dl=0

All manuals are here

If you have tightened them and still leaking, the only answer is to start again and use sealant. I’d you high temp rtv sealant

From your experiences what sealant would you recommend?
I see in manual:
Loctite® 574,
Volvo Penta 840879-1,
Permatex® No. 3,
Volvo Penta P/N 1161099-5,
Permatex® No. 77

but I always like to get experience of people doing it

 

[Mr Googler]

Permatex 77 is an RTV. Don’t think one does much more than the next but could be wrong

We are talking round the water way seals I assume. Be no good on the exhaust gaskets themselves obviously

 

[dr_oli]

Permatex 77 is an RTV. Don’t think one does much more than the next but could be wrong

We are talking round the water way seals I assume. Be no good on the exhaust gaskets themselves obviously

Those are gaskets between block and exhaust pipe where coolant flows. Gaskets are of metal (not sure which type).

 

[Mr Googler]

Permatex 77 is an RTV. Don’t think one does much more than the next but could be wrong

Those are gaskets between block and exhaust pipe where coolant flows. Gaskets are of metal (not sure which type).

There are rubber o rings at either end in addition to the metal gaskets at the exhaust. Best I hand over to Volvopaul the expert!

Do you know where along the manifold the leak is coming from to narrow it down?

 

[dr_oli]

I believe the leak is coming from the second and third cylinders near the turbo, but I'll remove everything next weekend to inspect it properly. The rubber O-ring is located on the opposite side of the turbo (towards the supercharger), and from what I can see, it appears to be in good condition.

I hope the issue is simply that the exhaust manifold/pipe isn't seated properly against the block — hope dies last. I'd rather not find out that the block or the exhaust surface itself is warped or uneven. Exhaust is new.

Did anybody used sealant on metal gaskets?

 

[dr_oli]

I went to the boat today and loosened all the manifold bolts. I then started retightening them in stages, beginning from the center and working outward and upward (the gasket was installed last week). Unfortunately, I wasn’t able to remove the turbo in order to take off the manifold completely, but I did manage to create a few millimeters of space between the manifold and the block. At first glance, the surface looked fine (by the way, the manifold is brand new).

I torqued the bolts gradually up to 40 Nm, but I’m still seeing a coolant leak. I could try replacing the gaskets again — even though they’re only a week old — but I’m not confident that will solve the problem.

What do you think I should do next? Should I consider using some kind of sealant? Or could it be that the block surface isn't flat?

 

[bowler]

When i changed my gaskets there was a weep at that torque setting. You could see coolant seep out but not alot.

An old hand who is a mechanic nipped them up a bit more using his preferred torque wrench, his elbow, and the weeping stopped.

D.

 

[Mr Googler]

When i changed my gaskets there was a weep at that torque setting. You could see coolant seep out but not alot.

An old hand who is a mechanic nipped them up a bit more using his preferred torque wrench, his elbow, and the weeping stopped.

D.

I’d take it off and start again making sure surfaces are clean on the engine. The “new” gaskets will be squashed now anyway

 

[dr_oli]

Problem resolved – Unfortunately, simply replacing the gaskets didn’t help much, so I checked whether the cylinder head was flat – and it wasn’t. The previous owner apparently had overheating problems and managed to “fix” them only temporarily (something he, of course, “forgot” to mention). After some time the issue reappeared. Once I replaced the cylinder head (it was only slightly more expensive to buy a Volvo-repaired head than to repair mine), the coolant loss stopped completely.