Request for help: problems with overheating old Volvo Penta engine

[Gary Matthesen]

I would like to repeat as stated much earlier, clean bottom and clean prop. You said the bottom was good. I had an issue starting to overheat this summer and had to nurse my way with light motor sailing back to the mooring, The prop had developed a good coating of barnacles. Took a swim with the scuba gear and did a thorough scrap of the prop blades. Checked and added to fresh coolant side of system and it made a huge difference.
Good luck on your trip.

[Kurlie1]

I had a similar problem with a VP 2003.
Turned out to be a clogged distribution pipe. A easy fix when you know.

[Clivevon]

FWIW I will add my 2 cents worth. I'm not a mechanic but my boat came with a Volvo MD17D engine which I ran for 15 years. That is a 3 cylinder version of the same engine you have.
You can find the workshop manual for the MD11C, D, & MD17C & D engine here:
https://l-36.com/read_pdf.php?page=5...orkshop_Manual

If your engine is seriously overheating, you effectively have almost no engine, or one you can only run for a short while each time. Problem needs sorting as a priority.

A few basics which might help.
Make sure the impeller in your sea water pump is good - sounds like it probably is but needs checking & a good idea to replace every year.

Those engines designed for indirect cooling come with an engine driven fresh water coolant pump driven by the fan belt, not an electric pump. The point is that the faster the engine is running, the faster the pump is working, whereas an electric pump runs the same irrespective of engine speed, so may be too much at tickover & not enough at full revs.

Obviously need to be sure your electric pump is actually running. If it is, are you sure it is big enough? Electric pumps are relatively cheap - plumb in a bigger one maybe?

Try running the engine without the thermostat - it will take longer to warm up but will show up if the thermostat is contributing to the problem.

Your indirect freshwater cooling system - actually probably 50% coolant - should be circulating through the engine block. The water channels are small & easily blocked - which is why direct sea water cooling is not a good idea. If the engine has been indirectly cooled from new, its hard to see what
could be causing any blockages.

That indirect system will have a water (coolant) reservoir which should be regularly topped up. If it is staying full, the problem lies elsewhere. If the reservoir needs frequent topping up, you have a leak somewhere - could be hoses, could be the pressure cap blowing (which could be caused by a head gasket leak pressurising the water system - what does your engine oil look like? OK - or milky?), could be a leak in the engine cylinder block itself (that was what killed my 30 year old engine), could be a leak in the heat exchanger. Is the anode still OK there?

If you are not losing coolant but the engine is still overheating, you have a problem somewhere.

If the pump runs & is big enough, look at your heat exchanger- is it blocked - you should be able to part dismantle it to check free running.

If all OK, check your engine block internal coolant pathways - try flushing through the engine block with a hose. Just be aware that if debris has found its way into your engine block over the years - silt maybe - then flushing or back flushing the block could possible make any blockage worse by shifting but not removing debris.

Are you sure the engine was always indirectly cooled from new? Not converted from direct cooling after some years use? Might benefit from flushing through the engine block if overheating persists. Take a look at how to flush through your engine here:
https://forums.ybw.com/index.php?thr...-engine.10263/ especially posts 7 from Vyv Cox - very authoritative source - & 15.

Hope some of that helps - good luck.

[Clivevon]

Originally Posted by Gary Matthesen

I would like to repeat as stated much earlier, clean bottom and clean prop. You said the bottom was good. I had an issue starting to overheat this summer and had to nurse my way with light motor sailing back to the mooring, The prop had developed a good coating of barnacles. Took a swim with the scuba gear and did a thorough scrap of the prop blades. Checked and added to fresh coolant side of system and it made a huge difference.
Good luck on your trip.

also makes good sense.

[team karst]

Its been mentioned, but worthy of repeating. In a wet exhaust system, steam is the easiest, fastest, and most reliable indicator of low raw water flow. If you have a hot engine, and there is water AND steam in the exhaust, there is not enough raw water being pumped. Then you head down the raw water checklist.
If no steam, and a hot engine, only then chase down air in coolant, thermostat, delaminated hose, and the other items on the closed coolant side.
Basically, divide the problem in half as soon as possible.
I have and use an IR gun. But dont expect magic. If the RW flow is low, it tends to make All the temperatures elevated. On all of my current and past engines, the steam test works better. Plus, easier and safer under load when solo.

[Boatyarddog]

Originally Posted by Allied39

The pump says 24 volt.
Are you getting 24 volts to the pump? 12 wont do it.
I would ensure pump operation, I like your idea of bucket to bucket to check , however as pointed out, priming may be an issue, but that should not be hard to get past.
Process of elimination, you are doing well by the sound of it.

I'm not seeing 24vt.
14vt. As that number goes to a 12 vt circulation pump.
59500 circulation pump
Boatyarddog

[Rdl]

Just fixed a similar issue with my 2002 Volvo with aftermarket fresh water cooling system, pump seem to be running but no circulation.
I removed pump and removed the 4 screws at impeller end and found that a small piece tie wrap end was jamming the impeller.
Everything is fine now.
Good luck

[Allied39]

Originally Posted by Boatyarddog

I'm not seeing 24vt.
14vt. As that number goes to a 12 vt circulation pump.
59500 circulation pump
Boatyarddog

Really?
In the last pic with the pump in what looks like his left hand on the left side of the pump I see 24 volt written.
Ah, who knows.
It's all academic anyhow as the fellow has not been back on so likely has his issue sorted....hopefully.

[petter5]

Warning: Do not remove the cylinder heads on a such old engine if it is not 100% confirmed that it is required.
Mostly this engine was delivered new from Volvo with salt waster cooling, and later the fresh water cooling system was fitted - the system i the photos seems like a "MAR TEK" system that was very popular late 1980 and onwards. These systems used electric centrifugal pump. During the period from 1988 and onwards, I did sell and install hundreds of these systems in that period, many of them on old Volvo engines like the MD1, MD2, MD3, or the later MD11, MD17 and MD34 etc etc.
The problem with removal of cylinder heads on these old engines that initially did operate with salt water cooling is that that due to salt water corrosion inside the coolant channels form before the fresh water cooling was fitted, might affect sealing surface of cylinder head and the cylinder block so that leaks will occur when assembling the engine again with new gaskets after repair, and render the engine un-repairable.


To find the source of your issue, First, be sure that the heat exchanger are clean inside, the salt water impeller are in good condition and that the flow on the salt water system are ok. On the fresh waterside, replace the 24 Volt pump with a 12 volt pump. Fill the fresh water system with coolant mixture and connect the 12V pump direct to the battery. Be 100% sure that the polarity of pump connections +- are correct so that the pump rotates the correct way. When 12volt are connected to the pump, the coolant should flow in the system, even if the engine is not running since the circulation pump is electric powered. Initially, you can also do testing, using only fresh water in the coolant system to avoid spilling a lot of antifreeze, but be sure to fill a minimum with 40% coolant mixture when you have solved initial problems.
If you suspect clogged cooling channels inside the engine, avoid opening the engine but rather clean the system inside with a acid solution. Many different products exist in the market, but also a hydrochloric acid can be used (take care) Also boiler descaling products can be effective.
Another thing that might make issues on these engines is the exhaust elbow. If in doubt - replace the exhaust elbow. Corrosion inside the exhaust elbow might affect salt water flow resulting in cooling problems.

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.

[Mongo_at_sea]

The thermostat should be removed and inspected, and easiest to just replace. If they ever had a problem with cooling prior to retrofitting with heat exchanger there could be bits of impeller still inside the thermostat. They move around, restrict flow.

[petter5]

The engine is of this question is fresh water cooled, and if a broken impeller, the remains of the impeller will be in the heat exchanger and not in the thermostat housing.
Except for that, I fully agree: The Thermostat must be fully functional.
The thermostat can be easily tested, even without a thermometer.
Take it out and putt in a kettle with cold water, put the kettle on the stove. When the water temperature is so hot that you fear to put your fingers in the hot water, the thermostat shall be fully open - if not replace the thermostat. Thermostats used in salt water systems normally open at 58-62 degree Celsius, and even if the system is converted to fresh water cooling like this engine - the old thermostat opening at 58-62 degrees is often still in place.

Originally Posted by Mongo_at_sea

The thermostat should be removed and inspected, and easiest to just replace. If they ever had a problem with cooling prior to retrofitting with heat exchanger there could be bits of impeller still inside the thermostat. They move around, restrict flow.

[MicHughV]

Warning: Do not remove the cylinder heads on a such old engine if it is not 100% confirmed that it is required.

I gotta say this....I remember removing the cylinder heads from my old raw water cooled Volvo...no once....but three times...over a span of about 10 years...each time using the same head gasket.....once cleaned and re-assembled, the engine ran fine....no problems...

was I lucky ?....maybe...but I had little choice as no spare head gasket was available to me at the time..

I've also had the entire engine filled with sea water....seized up tight...this prompted one of the times I removed the cylinder heads...to suck out the water....
I had to smack one piston with a sledgehammer to get it to move.
Remarkably, after cleaning, new oil, etc, the thing fired up and ran as it always did.

While I'm not a Volvo fan, I will readily testify that they are robust built engines, that can take serious abuse.

[OneBoatman]

Check these things:
Sea water strainer is clear.
Sea water impellor is new.
Is your fresh water side plumbed to heat your hot water tank? If so
and you have had the sytem open for coolant or hose replacement. Be certain there are no kinks and you do not have an air lock as it is this additional plumbing that is most prone to getting air bound after servicing. It must be burped by opening the reservoir pressure cap or in the extreme by temporarily connecting and raising an aux reservoir of coolant a couple of feet above the sytem to purge out any air, then restore to std config recheck coolant level.
Check heat exchanger at end nearest the se water pump for bit of impellor or blockae for previous overheat episodes perhaps some time in the past.
Check that you don't have extraordinary carbon builup in your exhaust mixing elbow, as this will cause the engine to overheat once it is bad enough to restrict the sea water flow. Boatman

[guitarrich]

I’ve read most of the posts, but not every word, so my apologies if I missed this…..

Exhaust (injection) elbow.

These need as much attention as a heat exchanger.

If these are left for any time, and then used again, the metal inside the elbow can delaminate and work like a sponge - expanding into the tube and causing it to become blocked.

I recommend removing the elbow to check. On any engine, this should be regularly checked, but especially if the engine has not been running for a few months or more.

[beaker]

FWIW: I own 2.5 MD1's (do not ask about the 1/2. :-)). The first was rusted through and through wen I got her with my first boat and took nearly a year to restore. The second was recently rebuilt and in Bristol fashion. Taking the head off to check scaling in water jacket should not be an issue. You will need to be careful with the oil feed line going to rocker arms as they need to be bent out of the way to clear head out.

But, I would humbly suggest that you bypass the heat exchanger and set up the original raw water cooling system first. This would eliminate a lot of tracing though other components. If It works and the engine stays relatively cool, you are at your leisure to trouble shoot the exchange system. Allowing use of your engine in the meantime.

Pulling the thermostat is a good idea also. the housing for the thermostat is designed with a bypass to at least get water into the jacket. Removing or loosening the drain plug for water jacket to see if water comes out will let you know if water is at least getting in there. I did this as a kid when I had a beat up old car and the radiator leaked.

Steam in exhaust would be another good indication but if no water in jacket, I think steam would be created. Ensuring water in jacket should allow this detection method to work. No water in jacket, you will not get steam.

Short of pulling head off, I have removed intake thermostat and exhaust manifold as well as water jacket drains and poked around with a stiff wire to break up anything loose in water jacket. If you get a lump of rust or anything else showing up, pull head or go with a cleaning agent as mentioned.

I have also reused the original copper gasket on head and had no issues. The current replacement version of this sold is lacking. There is a thin area between water jacket and cylinder bore and the 1/2 engine I have showed failure in this spot and water got into cylinder causing it to cease. If I had to ever replace my head gasket, I would mint up a new gasket from a copper sheet, not using the replacement gasket you get online.

As mentioned, "hot" is a relative term. Diesels like to run hot. get the IR device. If you are sure water is in jacket, run engine and constantly measure. If the IR flattens and a particular temperature and no steam, I would call it good.