Cam Belt

[runner911]

I currently run a Merry Fisher 655 fitted with a Volvo Penta
D3 110-B engine which has covered just over 700 hours.

The boat was built in 2006.

I service the engine every year but have never replaced the toothed cam belt.

According to the manual which came with the boat , the cam belt should be changed after 1400 hours engine running.

There is no mention of time span before the belt should be changed.

Whilst I don't wish to make work, I am just a little concerned about the age of the belt and whether material from which it is made has begun to degrade .

Has anyone else faced the same problem ?

Space between the front of the engine and the bulkhead is very limited and there is insufficient space to carry out a visual inspection.

 

[No Regrets]

There's an easy way to replace the cam belt, before it breaks, which is inevitable...

Run the engine, and using a stanley knife, split the old belt into two equal thin ones, carefully!

Then gently slacken the tension a bit, fit the new belt halfway along the pulley, then cut the old one off completely and re-tention.

Usually does the job...

 

[Keith-i]

Going by car standards it used to be 5yr intervals now increased to 7 years with modern materials. I would do it as a precaution. Heat cycling and time must age it just as much as use.

 

[burgundyben]

There's an easy way to replace the cam belt, before it breaks, which is inevitable...

Run the engine, and using a stanley knife, split the old belt into two equal thin ones, carefully!

Then gently slacken the tension a bit, fit the new belt halfway along the pulley, then cut the old one off completely and re-tention.

Usually does the job...

Bollocks.

 

[rafiki_]

Cam belts are a very bad idea if there is a danger of contact with water. The adhesives used to bond the various layers together are water based in my experience, hence water is a great solvent, hence belts delaminate in a damp environment. I would be very tempted to change every 5-7 years.

 

[No Regrets]

Bollocks.

My technicians used to do this for years whilst changing cam belts over the fifteen years I owned a garage.

Your call...

 

[burgundyben]

Run the engine, and using a stanley knife, split the old belt into two equal thin ones, carefully!

You'd take that risk with a customer engine? Nutter.

My technicians used to do this for years whilst changing cam belts over the fifteen years I owned a garage.

Your call...

I don't believe it.

One pulley on the whole train has cheeks on the side to stop the belt wandering off, in my experience, its often the one on the crank. There is no way on earth to get the new belt over the cheeks and onto the other pulleys.

Its a shit idea. Workshop manual written by tech pubs authors that work alongside engine design engineers do not tell you to do this. For good reason.

 

[Boat2016]

There's an easy way to replace the cam belt, before it breaks, which is inevitable...

Run the engine, and using a stanley knife, split the old belt into two equal thin ones, carefully!

Then gently slacken the tension a bit, fit the new belt halfway along the pulley, then cut the old one off completely and re-tention.

Usually does the job...

I have heard this one before but thought it was someone's idea of a joke, clearly not and wouldn't risk it with my engine !

 

[Racingfrank7]

There's an easy way to replace the cam belt, before it breaks, which is inevitable...

Run the engine, and using a stanley knife, split the old belt into two equal thin ones, carefully!

Then gently slacken the tension a bit, fit the new belt halfway along the pulley, then cut the old one off completely and re-tention.

Usually does the job...

So how do you replace the tensioner and guide pulleys that you get in a cambelt kit ?

I'm with Ben.

Do it properly.

 

[petem]

Are the KAD42/44/D3/D4, etc 'interference engines'?

 

[burgundyben]

Are the KAD42/44/D3/D4, etc 'interference engines'?

i'm fairly sure no modern engine is safe in that regard, especially a modern diesel, they'd never achieve the compression. Some engines had features milled into the piston crown to give more clearance, but that adds cost and brings all sorts of mech and thermal FEA issues (I have worked in engine development).

Non interference engines are few and far between.

ETA - why would they need to be? Follow the maintenance schedule and use a belt manufactured in a modern process with its quality assurance and control and belt snappage will be rare.

 

[petem]

ETA - why would they need to be? Follow the maintenance schedule and use a belt manufactured in a modern process with its quality assurance and control and belt snappage will be rare.

Just curious.

 

[[2068]]

Just curious.

D4/D6 does not have any kind of cam belt - it has chains.
KAD series engines have gear driven camshafts.
D3 is the odd one out, derived from a car engine, it has a cambelt.

.

 

[petem]

D4/D6 does not have any kind of cam belt - it has chains.
KAD series engines have gear driven camshafts.
D3 is the odd one out, derived from a car engine, it has a cambelt.

.

Thanks, I did wonder.

 

[MrB]

You'd take that risk with a customer engine? Nutter.




I don't believe it.

One pulley on the whole train has cheeks on the side to stop the belt wandering off, in my experience, its often the one on the crank. There is no way on earth to get the new belt over the cheeks and onto the other pulleys.

Its a shit idea. Workshop manual written by tech pubs authors that work alongside engine design engineers do not tell you to do this. For good reason.

This guy apparently works for Mercedes as a video salesman. I have had a few run-in's with him and every time he has proved a total numpty. :sleeping:

 

[[2068]]

This guy apparently works for Mercedes as a video salesman. I have had a few run-in's with him and every time he has proved a total numpty. :sleeping:

Changing belts that way might be quick, but the proper procedure usually involves a locking tool to keep the camshafts in the right place, plus the replacement of tensioners, and possibly the water pump as well, depending on the engine and the mileage.

 

[penberth3]

Changing belts that way might be quick, but the proper procedure usually involves a locking tool to keep the camshafts in the right place, plus the replacement of tensioners, and possibly the water pump as well, depending on the engine and the mileage.

I'd expect the sort of person who puts their fingers AND a Stanley knife near a moving belt to ignore proper procedures. And then charge the customer for the tensioner and water pump they haven't fitted.

 

[Heckler]

My technicians used to do this for years whilst changing cam belts over the fifteen years I owned a garage.

Your call...

Technicians? Sounds more like shade tree mechanics!
Stu

 

[Trundlebug]

There's an easy way to replace the cam belt, before it breaks, which is inevitable...

Run the engine, and using a stanley knife, split the old belt into two equal thin ones, carefully!

Then gently slacken the tension a bit, fit the new belt halfway along the pulley, then cut the old one off completely and re-tention.

Usually does the job...

I love the use of the word "Usually".
Did you leave out, "...but when it doesn't it's a new engine job?"
Not the kind of risk I'd want to take thanks

 

[No Regrets]

Oh this was a few years ago, before the advent of 'One belt drive all' and not good for 24V V6's which have 7' belts and multiple plastic pulleys which need replacing, but should work on a simple old technology boat engine such as a small Diesel. It was done on a case-by-case basis. The mechanics knew which would and wouldn't work.

In those days, you didn't get pulleys and tensioners to replace like the modern rubbish. Most of that stuff fails before the actual cam-belt if you're unlucky.

I also wonder about the timing belt intervals these days! 95,000 miles!? Citroen and Peugeot had the same engines, Peugeot recommended 36000 mile changes, Citroen 72,000 miles....yet the Citroens would often fail between 50 and 60,000 miles.

However, the technique works. The Stanley knife is simply gently pressed against the belt from the top, no risk of personal injury if you're careful.