KAD300 - advice on supercharger rebuilds

[frazion]

Hi folks, my port engine started overheating this year. While in the water, I've changed the impeller, flushed the raw water and internal coolant systems (oxalic acid flush), no joy, checked the temps with an ir gun and sure enough, its hot alright. Specifically the supercharger heats up so much faster than the SB charger. I drained the oil and its a horrible grey goo colour....not good...refilled, and now that the boat is out the water i checked the oil again with a drain and its still grey. I kinda expected that since i wasnt going to get all the old oil out in the first go...I'm also not sure why an overheating supercharger would make the engine overheat but its clearly an issue so one thing at a time. So, the compressor is removed, the heat exchanger is removed and im about to pressure test the heat exchanger. I figured i would remove the compressor sump, and check it out, ensure all the oil is cleaned out and see if there are any metal bits in there that indicate wear.

I'm aware these are stupid expensive so i'm thinking it would be an idea to send to a pro for a refurb, preferably one that does an assessment before just doing a rebuild! worst case, ill make a youtube of taking it apart cos i cant seem to find one!

Thats a long winded post but the question really is:

1) Anyone experienced dirty grey oil in the compressor before and what was it (im hating the idea but im thinking dodgy bearings and other unfun guff)
2) Recommendations and cost expectations for a compressor review and rebuild

ta fanks.

 

[petem]

I'm no expert but from what I understand, a small amount of any old oil can give new oil a grey colour. So another oil change might be worth doing. Does the compressor sound and run OK?

Ref your overheating, have you tried to rebuild the sea water pump? These can be affected by worn cams, impeller covers, etc IIRC.

Also, and I'm not sure it's an issue on these engines, but are all the cooling pipes OK? Could one of them be collapsing which is restricting flow? Are there any other blockages in cooling system?

@volvopaul any thoughts?

 

[frazion]

Thanks for the response. The sea water pump was rebuilt recently and although i didnt change the cam, just the bearings and seals, the throughput is observably hefty with a nice cool feel on the now new faceplate of the raw water pump. no blockage in the strainer and all pipes are observably not collapsed. i also checked the exhaust elbow and although its rusty as expected, its not blocked. Theres plenty brown goop in the reservoir tank, this engine feeds the calorimeter so ill be running another oxalic rinse to try and reduce that build up again. ive just thought that i havent checked that the thermostats open at the right temps so will bring them home for a boil on the hob and an IR gun check (shhh dont tell the wife!). But....if i watch the temps on both engines started at the same time, the increase rate on the port from cold is noticeable faster that SB. so while ill check the thermostats anyway, theres still a more rapid increase in temps pre-thermo.

the compressor blows plenty but to my ears sounds a bit gritty when running. just looked at the o-ring price. £50 for a gasket....crazy.

 

[petem]

@BruceK is also knowledgeable about these superchargers.

This thread may be useful... Volvo Supercharger (KAD) servicing

 

[Mr Googler]

Electromagnetic Clutches and Brakes - Ogura Industrial Corp -

Worth a call?

 

[jon and michie]

Where the air pipe (approx 2" diameter black pipe) goes into the back of super charger did any of it leak air ? on my old boat it did see at the bottom of page 2 here

Thread 'Kad 300 lagging'

26 Aug 2019

Hi - I have found this weekend that the engine would get to 2500rpm easily but would take a while to get to 2900rpm never mind any higher.
I opened the hatch whilst docked and started the engine and looked at the supercharger clutch which appears to be engaging.
But I did notice at the rear of the charger where a large black pipe goes in air appeared to be coming out.
Should the connection between the charger and the pipe be air tight?
If this is the cause of the "engine lag"
Is there some sort of seal kit that is easily available.
And is it an easy fix?

An opinions welcomed
Jon

• jon and michie
• Replies: 33
• Forum: Motor Boat Forum

mine was leaking air because of the sealant used by volvo had basically worn away.

This is my thinking / opinion - If its leaking then the chances are the turbo cant take over which in turn the supercharger could be working overtime which in turn equates to more heat for the Supercharger

 

[tico]

Is the faster heat up rate down to the stbd engine heating the water in the calorifier?

 

[BruceK]

Hi folks, my port engine started overheating this year. While in the water, I've changed the impeller, flushed the raw water and internal coolant systems (oxalic acid flush), no joy, checked the temps with an ir gun and sure enough, its hot alright. Specifically the supercharger heats up so much faster than the SB charger. I drained the oil and its a horrible grey goo colour....not good...refilled, and now that the boat is out the water i checked the oil again with a drain and its still grey. I kinda expected that since i wasnt going to get all the old oil out in the first go...I'm also not sure why an overheating supercharger would make the engine overheat but its clearly an issue so one thing at a time. So, the compressor is removed, the heat exchanger is removed and im about to pressure test the heat exchanger. I figured i would remove the compressor sump, and check it out, ensure all the oil is cleaned out and see if there are any metal bits in there that indicate wear.

I'm aware these are stupid expensive so i'm thinking it would be an idea to send to a pro for a refurb, preferably one that does an assessment before just doing a rebuild! worst case, ill make a youtube of taking it apart cos i cant seem to find one!

Thats a long winded post but the question really is:

1) Anyone experienced dirty grey oil in the compressor before and what was it (im hating the idea but im thinking dodgy bearings and other unfun guff)
2) Recommendations and cost expectations for a compressor review and rebuild

ta fanks.

The clue is in the goo. The back bearing is shot. The oil leaks onto the root vanes and adds a lot of friction to them when they spin. Confirm if vanes are sticky or goo is in pipes and CAG cooler. Unfortunately there is no refurbishment possible on these for this. You are limited to clutch and front bearing only. The rear bearing is epoxied in and cannot come out without catastrophic damage. If that bearing is gone it's a new or good secondhand one I am afraid.

 

[aerobat]

The clue is in the goo. The back bearing is shot. The oil leaks onto the root vanes and adds a lot of friction to them when they spin. Confirm if vanes are sticky or goo is in pipes and CAG cooler. Unfortunately there is no refurbishment possible on these for this. You are limited to clutch and front bearing only. The rear bearing is epoxied in and cannot come out without catastrophic damage. If that bearing is gone it's a new or good secondhand one I am afraid.

Wow . Never heared about this . I assume a first sign is the compressor needs topping up oil frequently ?

And how does this explain engine overheating ? Surely not from the additional friction of the compressor ?

 

[Mr Googler]

My guess would be 2 separate issues

I’d be checking the elbow for the overheat

 

[BruceK]

And how does this explain engine overheating ? Surely not from the additional friction of the compressor ?

It doesn't other than confirm why his

checked the temps with an ir gun and sure enough, its hot alright. Specifically the "port" supercharger heats up so much faster than the SB charger.

However what one must also understand is that the cooling of these engines is 3 fold. The coolant the oil and the air temps. We all understand what the coolant does but these engines also use oil to cool the underside of the piston and liners. Whats less well understood is that up to 30% (dont quote me on that its a while since I read the design manuals) of the cooling is also through forced air induction. It cools the piston crown and the residual heat from the last stroke's burn. Just like blowing on your soup spoon to chill it. So if your turbo's or root charger or Charge air cooler are not forcing cold, dense, pressurized (the more the pressure the greater the heat sink) air in, at less than 40 C at intake manifold, you WILL experience an overheat situation at any meaningfull engine load above 1400 rpm .... period, because you havent cooled the last burn stroke down. This is exacerbated because you are pumping more fuel in to try and make good the shortfall in power. These are blown engines. If they are not delivering more than the "naked" blocks 100odd hp its almost always the forced induction side of things

 

[aerobat]

Whats less well understood is that up to 30% (dont quote me on that its a while since I read the design manuals) of the cooling is also through forced air induction. It cools the piston crown and the residual heat from the last stroke's burn. Just like blowing on your soup spoon to chill it. So if your turbo's or root charger or Charge air cooler are not forcing cold, dense, pressurized (the more the pressure the greater the heat sink) air in, at less than 40 C at intake manifold, you WILL experience an overheat situation at any meaningfull engine load above 1400 rpm .... period, because you havent cooled the last burn stroke down. This is exacerbated because you are pumping more fuel in to try and make good the shortfall in power. These are blown engines. If they are not delivering more than the "naked" blocks 100odd hp its almost always the forced induction side of things

Do you have any credible source to this statement ? While its true that these engines depend heavily on boost pressure i never heared this serves for engine cooling even when somebody could imagine it .

The engine , getting way more air into the cylinders than it could suck in naturally aspirated , burns way more fuel for the combustion than it could do when naturally aspirated . The goal by burning more fuel than "naturally" possible is to have a more powerful combustion with a higher
output . This all in all results in a higher heat generated by the engines and not a cooling effect .

Imho the higher the boost pressure the more fuel can be burned and finally the higher the power output , i never heared the higher the boost pressure the cooler the engine runs !

 

[gjgm]

I guess that cool air going in not only increases possible output, but it does so more efficiently than otherwise, and if it doing so more efficiently, I guess overall it is producing less heat? Not quite the same as actually "cooling" the piston, but not heating it up as much,maybe?

 

[BruceK]

Do you have any credible source to this statement ? While its true that these engines depend heavily on boost pressure i never heared this serves for engine cooling even when somebody could imagine it .

The engine , getting way more air into the cylinders than it could suck in naturally aspirated , burns way more fuel for the combustion than it could do when naturally aspirated . The goal by burning more fuel than "naturally" possible is to have a more powerful combustion with a higher
output . This all in all results in a higher heat generated by the engines and not a cooling effect .

Imho the higher the boost pressure the more fuel can be burned and finally the higher the power output , i never heared the higher the boost pressure the cooler the engine runs !

Credible. Yes its a rash on the internet if you bothered to use any search function. I dont have the design manual on me but Gemini will give you this answer for instance

"While specific, published percentage data for the charge air cooler (CAC) on older Volvo Penta KAD (e.g., KAD42/43/44/300) engines is not readily available in public, technical, or forum sources, the charge air cooler in high-performance marine diesel engines typically handles a significant portion of the total thermal load to manage the heat generated by turbocharging
.

• Role in Thermal Load: The charge air cooler (aftercooler) reduces the temperature of compressed air, which directly reduces the maximum cylinder pressure, exhaust temperature, and overall thermal loading on the engine.
• Heat Rejection Context: In similar, modern high-performance, turbocharged marine diesel engines, the charge air cooler often removes a very high percentage of the heat, sometimes exceeding that removed by the primary engine water cooling system at full load, due to the high boost pressures required for high power output.
• KAD Specifics: On KAD engines, which use both a supercharger and a turbocharger, the charge air cooler (which is usually sea-water cooled) is critical for reducing the high intake air temperatures generated by the turbocharger, particularly at high RPM.

Key Takeaway: While I cannot provide a precise, verified "X%" figure, in heavily turbocharged marine engines like the KAD series, the charge air cooler acts as a critical, high-capacity heat sink. It is considered one of the primary components alongside the main heat exchanger, requiring regular service to prevent overheating. "

 

[BruceK]

Asking the question a different way will yield this

"
Yes, a
charge air cooler (intercooler) and forced induction system (turbocharger/supercharger) indirectly play a significant role in cooling the piston, cylinder, and combustion chamber in a diesel engine.
While the primary, direct cooling of the piston and cylinder is handled by engine oil (via piston cooling jets) and liquid coolant, the charge air cooler ensures the intake charge is dense and cool, which directly reduces the thermal load on these components.
Here is how they contribute to cooling the piston/cylinder:

• Reduction of Intake Temperature: The turbocharger compresses air, heating it significantly (often over 100°C). A charge air cooler (CAC) cools this air down to near ambient temperatures. Cooler air enters the cylinder, resulting in a lower starting temperature for the combustion cycle, which prevents excessive heat buildup.
• Reduced Thermal Loading: By lowering the peak combustion temperatures, the charge air cooler reduces the extreme thermal stress on the cylinder head, piston crowns, and exhaust valves. This prevents components from warping or cracking due to excessive heat.
• Lowering EGT (Exhaust Gas Temperature): Cooler intake air leads to more efficient combustion, reducing the temperature of the exhaust gases that pass through the cylinder and out the exhaust valves.
• Preventing Damage: Without a charge air cooler, high-boost engines would experience dangerously high intake temperatures, which can lead to weakened "hot spots" in the engine and early component failure.

Summary: The charge air cooler acts as a critical component in managing the overall thermal health of the engine, ensuring the cylinder and pistons do not overheat, thus increasing engine longevity and reliability. "

 

[BruceK]

The final point to be made as it is secondary is as the cooled air is denser as it enters the engine it has a greater heatsink capacity

"
Yes, high-pressure gases provide a significantly better heat sink—and therefore better cooling—compared to a partial vacuum
. While a vacuum is an excellent thermal insulator, high-pressure gases act as a medium for convective heat transfer, allowing heat to be carried away from a hot object more effectively.
Why High-Pressure Gases are Better Heat Sinks

• Increased Particle Density: Higher pressure means more gas molecules per unit volume. More molecules are available to absorb thermal energy from the surface of an object.
• Convection Efficiency: High-pressure gases (such as Nitrogen or Helium used in vacuum furnaces) can be circulated to create convection. Convection is far more efficient at cooling than radiation alone, which is the only mechanism available in a high vacuum.
• Enhanced Quenching: In industrial applications, increasing the pressure of a quenching gas leads to faster cooling rates and higher peak surface heat flux.

Key Considerations

• Heat Capacity vs. Conductivity: While higher pressure adds more "mass" (molecules) to store heat, it does not necessarily increase the speed at which that heat transfers (thermal conductivity) dramatically. The benefit is mainly in the higher total capacity to absorb heat.
• The "Pressure" Factor: An increase in pressure increases the density, which increases the cooling rate.
• Optimal Range: The cooling performance is often related to the pressure of the gas, but there is a limit where further increases in pressure offer diminishing returns on thermal conductivity, as the molecules become so crowded that their ability to transport heat doesn't increase proportionately. "

 

[Seastoke]

The final point to be made as it is secondary is as the cooled air is denser as it enters the engine it has a greater heatsink capacity

"
Yes, high-pressure gases provide a significantly better heat sink—and therefore better cooling—compared to a partial vacuum
. While a vacuum is an excellent thermal insulator, high-pressure gases act as a medium for convective heat transfer, allowing heat to be carried away from a hot object more effectively.
Why High-Pressure Gases are Better Heat Sinks

• Increased Particle Density: Higher pressure means more gas molecules per unit volume. More molecules are available to absorb thermal energy from the surface of an object.
• Convection Efficiency: High-pressure gases (such as Nitrogen or Helium used in vacuum furnaces) can be circulated to create convection. Convection is far more efficient at cooling than radiation alone, which is the only mechanism available in a high vacuum.
• Enhanced Quenching: In industrial applications, increasing the pressure of a quenching gas leads to faster cooling rates and higher peak surface heat flux.

Key Considerations

• Heat Capacity vs. Conductivity: While higher pressure adds more "mass" (molecules) to store heat, it does not necessarily increase the speed at which that heat transfers (thermal conductivity) dramatically. The benefit is mainly in the higher total capacity to absorb heat.
• The "Pressure" Factor: An increase in pressure increases the density, which increases the cooling rate.
• Optimal Range: The cooling performance is often related to the pressure of the gas, but there is a limit where further increases in pressure offer diminishing returns on thermal conductivity, as the molecules become so crowded that their ability to transport heat doesn't increase proportionately. "

That’s the longest , up yours I ever read but never understood.

 

[BruceK]

That’s the longest , up yours I ever read but never understood.

when you burn your hand on the exhaust again spit and then blow on it and all will become clear

 

[Mr Googler]

when you burn your hand on the exhaust again spit and then blow on it and all will become clear

Ha! You need running engines for that to happen. No issue for Marina Queen

 

[BruceK]

Ha! You need running engines for that to happen. No issue for Marina Queen

I was going to remind him about Boyles Law and to notice how his aerosol underarm deodorant feels cool when he spays his pits, but remembered the stink and lack of meaningful education. Some people are beyond help even if you beat them with a stick.