Request for help: problems with overheating old Volvo Penta engine

[Sailmonkey]

Originally Posted by MicHughV

I well familiar with this problem, having owned salt water cooled Volvo's before.

The fix is to remove the cylinder heads.
When you do so, you'll expose the water cooling openings and passages around the cylinders.
You will likely also note, that salt water and other crud have all but blocked these openings.
You will have to clean these openings and passages out.
I used a a file, screwdriver, knife blade, whatever I could find that would fit inside those small openings and passages.
The pieces of crud will eventually be flushed out.

I re-used the cylinder head gaskets, and never had any problem, with engine overheating problems after that.

You should also check the raw water impeller for wear, not only the rubber impeller, but also the outside plate, as this must sit flush with the impeller to work properly. It's not uncommon to have small particles of grit get in here and wear a groove into that plate.This will allow air between the plate and impeller, causing inadequate water flow.

The pressure tank is not the problem, this is a container that controls the coolant water in the heat exchanger.

It's a good idea to add some "anti-freeze" to this container to prevent cooling water freeze up.

Now……please explain how in the same post you acknowledge that the engine has a coolant tank and that there can be salt crud in the cylinder heads.

[MicHughV]

Volvo doesn't make those old engines anymore, but in the day, they were work horses.
They are incredibly tough engines, and can take a terrific amount of abuse.

After 40 years, its all the "other stuff" that needs attention.

Seriously, remove the cylinder heads and address all the other various components suggested here, and it will likely run for another 40 years.

One last piece of advice. Volvo charges an arm and leg for their engine parts. I was often able to find parts, filters, etc, elsewhere for 1/10th a Volvo price.
Oil filters is a classic example. Volvo wants a small fortune for these, but take that part number to any auto dealer and they can cross reference it for a similar item at a substantially reduced price.

And don't forget the internet. Many of those older engines or parts for them, can be found online from a variety of sources.

[MicHughV]

it was originally raw water cooled.....I suspect the heat exchanger was added to remove the salt water inside the engine issue, the heat exchanger does not look like any factory model....but it doesn't take long for the crud to build up. The crud was likely there, before the heat exchanger was added.
I've owned two Volvo's and it doesn't take but a year or two for the salt crud to become an issue.

[Allied39]

If I read his original post correctly this engine was delivered set up with heat exchanger from day one.
So likely salt buildup in the engine is not his issue.
Not being sarcastic or nasty, just pointing out something that seems to have been missed.

[Bill Seal]

That is not a factory fresh water system. The stock one has a belt driven circulation pump and plastic expansion tank.
(and is designed to overheat if air gets into the raw water circuit)

[MicHughV]

Allied, I hear ya.....but that heat exchanger in the photo is not a Volvo part....for one thing, it is not painted green, it is not cast either, as it would have been were it a Volvo part, it looks " fabricated" to my eye.....it may have been delivered and installed as such, but that heat exchanger was an "add on"....I'm pretty confident the engine ran as a salt water cooled engine in it's initial life, it may even come from another boat at one time and placed in this boat. That engine served as a raw water engine in many a fishing boat in it's day. Late 70's, early 80's...

It would be a simple matter to take one cylinder head off for a quick looksee..the cylinder heads are independent of each other.

Most any Volvo diesel engine owner in a sailboat that I have come across in my years on the water have a profound animosity about these engines.
I think they are well built and bullet proof, but they have some quirks that can be very annoying.

My advice remains the same, remove a cylinder head for a looksee. If the cooling passages look bad, the second cylinder will likely be the same.

If no blockage is discovered, you will at least have eliminated one source of potential trouble.

While I'm at it, the heat exchanger could also be a problem area. I can't say how this one was fabricated, but they are also relatively easy to open and check.

I would certainly check these two areas first, before moving on to other possible trouble spots

I've owned Volvo's with...and without heat exchangers..and have experience crud in both the cylinder cooling passages and exchanger.

Off course, one needs to check all the usual areas, strainer blockage, impeller housing, etc.

just my 2c....

[Strabo]

The after market indirect cooling unit was sold in US as a as a Sendur unit. Early models employed a freshwater pump with common shaft from seawater pump. Method to separate sea water from fresh was an o-ring. Issues could a occur if engine over heated. This is information only and do not believe underlying issue.

[MJH]

Originally Posted by bacchant

Hi fellow cruisers, I am currently off the coast of Sweden heading south to escape the cold, but has encountered a problem I was hoping someone here could help me with. I have limited technical experience and have purchased an old Bacchant IV ocean crosser that is somewhat more of "a repair project" than expected..Please excuse my ignorance, I have no formal training and don't know what I am doing....I learn everything by trying and failing and trying again while consulting some books and youtube combined with asking stupid questions..

The engine is a Volvo Penta MD 11c (almost 40 years) is overheating. Yes, it is due for replacement, but I really want to make it last a little longer if possible.. This particular engine model was originally salt water cooled (direct cooling), but was delivered with a heat exchanger and pump as add-on from day one. It is therefore fresh water (indirect) cooled despite the manual saying something else.. I have taken apart the raw water cooling system, serviced it and put it together again. This part now works well from seawater inlet, filter, sea water pump with impeller, heat exchanger, exhaust bend and all the way until exhaust outlet.

However, while the heat exchanger remains relatively cool the engine block becomes way too hot. I therefore assume the enclosed loop of cooling liquid in the heat exchanger is not circulated through the engine block as it is supposed to. As far as I understand it is either something wrong with the mechanical thermostat regulating flow into the engine block (opening up and letting coolant through when temperature exceeds 60-something degrees Celsius) or the external pump installed to push the coolant through the heat exchanger and the engine block. I have taken out and tested the thermostat in a cup of hot water and it works well, so now I am left with the pump...

Then comes my potential idiot-question: how to test a pump like this? I took a similar-looking pump that I removed from under a sink and tested it with a multimeter to confirm resistance. That seems ok. Then I connected it to a battery and confirmed that it rotates/spins. Again, ok. But when I connected hoses to it and tried to move water from one bucket to another no water goes through.. why? Another thing that confuses me is that of the two electric cables from the pump installed and connected to the heat exchanger one goes to the alternator while the other is only connected to a bolt on the engine itself.. That seems like grounding, but will that allow electricity to pass through and drive the pump?? When the engine is running there is no way to hear or see whether the pump is actually working / pushing coolant around.

Hope someone out there more knowledgable and experienced than I can help with some advice, I would be extremely thankful for any support on this one!

p { margin-bottom: 0.25cm; line-height: 115%; background: transparent }

First, let me congratulate you on the looks of this 40 year old engine...so clean. You are fastidious.

How long have you owned this boat/engine and is this a new problem? That is, has it run cooler before or always run hot?

Your description uses subjective measurements, "...while the heat exchanger remains relatively cool the engine block becomes way too hot." How hot is hot? My subjective measurement of hot will be different from yours. (On my Volvo Penta D2-55B I can't touch either because they are so hot.) I would use my Infrared Thermometer to get a precise measurement as to what "too hot" means compared to "...heat exchanger remains relatively cool." Perhaps with those objective readings you can determine if you truly have a problem, perhaps from Volvo Penta.

You say, "Please excuse my ignorance, I have no formal training and don't know what I am doing." Beautiful engine aside, this makes me question your work, "I have taken apart the raw water cooling system, serviced it and put it together again. This part now works well from seawater inlet, filter, sea water pump with impeller, heat exchanger, exhaust bend and all the way until exhaust outlet." How can it now be working "well" if the engine is "too hot"?

Perhaps you should service the engine with Barnacle Buster Concentrate for the recommended limited time before flushing the raw water system.

Good Luck.

~ ~ _/) ~ ~ MJH

[AlanR]

I have a similar setup, and had an overheating problem. Remove the cap from the heat exchanger, and start the engine. You should see the return coolant running into the coolant header tank, just under where the cap was.

My problem was a little but of dirt in the spigot where the flexible return pipe joins the header tank. I removed the pipe and ran a 1/8" drill but through the spigot, and all was well.

I was surprised at how little coolant is returned. More a trickle than a flow, but it is enough.

Check that your thermostat has a small (1/8") hole through it to allow a amall flow, to ensuree that it sees the temperature of the water. Some thermostats do not have this hole, so cold water stays in it.

Good luch.

[Stewie12]

Try running the engine without the thermostat and see if it runs cooler.

[MicHughV]

I'm curious to know what year this boat is and if that engine is the original engine.

I googled these boats online and some of them are quite old....70 something years..if that were the case, it may be that this particular Volvo was not the original engine.

[MicHughV]

my first Volvo was raw water cooled...it never ran very hot....60c= 140f, or thereabouts, this is apparently a feature of raw water cooled engines, the run cooler than their heat exchanger cousins...
over a 10 years span, I seem to recall having to ream out the cooling water passages 3 times.
I would know it was time, by observing steam coming out of the exhaust together with the water.....though the passages were notably clogged, the engine seemed to always run ok.

[MBWhite]

A very handy gizmo to have on a boat nowadays is an optical (also called IR, laser, or pyrometer) thermometer. Bottom line ones are ridiculously cheap and the really useful ones that read to ~600C and have a laser beam where they are pointed at still start around $20 USD. Just use one to follow the cooling passages both forward and backwards and it will show you where the coolant flow is blocked or restricted and how often the thermostat cycles. They will also tell you how hot your oven is, how cold the milk is, which bearing is bad on an electric motor, which cylinder isn't firing on an engine with a miss, and all sorts of other temp related things.



I heartily recommend anyone who does not already have one get one at some point. They all work well enough so no real need to get an expensive one especially in a marine environment as you might need to replace it eventually.

[Mike Banks]

Check your engine thermostat. Most engines have one.

[Cheechako]

The electrical pump is for engine cooling? That's a weird way to do it. Obviously done as an easy shortcut. You should have a belted pump.
Thermostats rarely fail but that could be it.
It can also be air trapped in the thermostat housing. If so, then the thermostat never heats up enough to open because it's surrounded by air not water.. Dont ask how I know! But this is unlikely unless you have drained the water out or had the engine apart.