Volvo D4-300 overheating.

[bill46]

Our 2014 RT31CB still overheats over 3000 RPM. Diver cleaned raw water scoop, Mechanic heat exchanger, oil and transmission heat exchangers, check all hoses, strainer is clean, plugged raw water wash down, changed impeller twice, replaced coolant and finally thermostat, which required replacing coolant again. It gets to 185 after warmup, and stays there from idle to 3000 RPM, then gets hot, over 205 where it lowers power, over that. WOT is 3450-3500 as it was when new.. Has anyone had a bad circulating pump on closed system? That is all I can think of now.

 

[quinsky]

D4 overheating seems to be a common issue and has been addressed in many other threads. I too suffer this malady with my D4 260. I've taken all the steps you have except changing the thermostat. My mechanic is of the opinion that thermostats don't go bad very often and when they do they fail completely. In the other threads someone suggested disconnecting and plugging the raw water wash down that feeds off the raw water strainer. This is a potential source for loss of pressure. I installed a shut off valve a few inches past the strainer. Haven't put the boat in the water yet so don't know if it will help. Others have seen an improvement. I also installed a cutoff valve in the raw water intake to the head. I use fresh water to flush since I added a 30gal water tank. (Another subject of much discussion). Good Luck.

 

[Brian B]

There have been issues with the multiport sea strainers. Remove and plug the ports for the wash down and head and see if temps improve. Also make sure the strainer cover is not cracked and makes a good seal.

 

[dclagett]

I don’t know what type of raw water pickup you have, however on my RT25SC it was a clam shell looking device. On my boat this device is near impossible to completely clean internally without removing it from the hull which requires hauling the boat. This was the cause of my overheating. Look in my album which will show you what I did to solve my overheating. Good luck.

 

[knotflying]

Check your oil cooler. This is a known area where the sea grass and other things accumulate and cause a restriction of flow. Cleaning that out often takes care of the problem. I would disagree with your mechanic regarding a bad thermostat as the first culprit. The thermostats are fairly reliable. The other culprit, as stated above could be air infiltrating from the head or the raw water. Check your oil cooler first. If that is clear then try plugging the raw water hose an then check performance. If you still have the problem then plug the raw water hose and check again. Let us know how you make out.

 

[dclagett]

A good indication if you are getting air in the raw water system is to look at the large sea strainer. If it is not completely filled with water, i.e. you see a bubble thru the clear plastic, then you raw water system is not operating a 100% efficiency. This could be do to a blockage somewhere in the pickup or the head/raw water wash down introducing air into the system.

 

[NautiTug]

It is interesting to note that on the new D4 (mine is 2017) they now have their own sea strainer and no longer pull off the multi port which now only is for the head and raw water washdown.

 

[BB marine]

Two water pump impellers changed, did both look normal with normal wear? Did the mechanic pull end caps off aftercooler? I believe that is the first cooler in line next is the heat exchanger. End cap also pulled and inspected? Then the reverse gear cooler is last before it goes to the exhaust elbow. Inspected and cleaned? (D4's that I have seen). If your mechanic inspected each of the components and they were clean of debris and buildup I would say the engine raw water side is good. If you have isolated the additional supplies at the sea strainer (if it has them Head and raw water wash down) that should eliminate air sucking into the system. Also as already mentioned inspect the strainer lid, cracked or seal damaged.. The pickup on the hull has been cleaned that eliminates that. Did you back flush from the strainer to the thru hull to confirm that the hose, sea cock and thru hull are clean without restriction to the hull pickup on the bottom? If so and that is clean. I think the raw water side is good. When troubleshooting raw water systems for air leaks I used a 2' long clear hose with a barb fitting. I would remove the hose off the suction side of the seawater pump and install the clear hose to the pump and slide the raw water suction hose on the barb fitting of clear hose. Then test run and look for air bubbles. If the hose showed good solid flow of water I was comfortable that the demands of the pump were being met. You can also perform this test at the end of the line( reverse gear cooler to mixing elbow) to see is there is good visible flow at the rpm where over heat begins. If all this checks out I would remove inspect the thermostat if it looks good I would test it in hot water to confirm it is opening to specifications. Regardless good or bad I would install a new thermostat if you removed it. Have you changed anti-freeze recently? If so is the system bleed ? Air in the closed cool side can also cause higher temperatures or small closed cooling leaks. I would inspect all fittings ,tighten clamps. This is a start. Good luck!

 

[Aquadogs]

There are a few things that come to mind that I havent seen mentioned here. 1). Have you considered the belt, it could be slipping at the higher RPM. 2) When the impellors were replaced was there any signs of blade damage or piece's missing. If something such as a peice of impellor blade got into a coolant galery within the engine it could be jambed into a position that is impedeing flow. This type of thing generally gets caught at or prior to the thermostat. 3) is the exhaust end of the cooling system flowing as designed? A small blockage could also restrict outfall flow at the higher RPM range. If the water cannot flow out it will have trouble entering the system as well.

Sent from my SM-T560NU using Tapatalk

 

[bill46]

Thanks all
Impellers looked like new.
Will take exhaust injection apart and check water to water heat exchanger again, Mechanic might have thought air cooler was water exchanger.
Next week

 

[knotflying]

I know it is a PIA, but when you "looked" at the impeller did you check to make sure the shaft spline was not loose and able to spin when you applied rotating pressure. That was one of the problems Capstu had. He was overheating at higher RPM's. It turned out that one of the culprits was the impeller slipping on the shaft.

 

[quinsky]

Ran my C28 for the first time after installing a shutoff valve in the raw water wash down uptake. Max temp while running WOT was 196. Before, it would get up to 210 and cut back rpms. HOWEVER, outside water temp is much cooler. I watched the strainer while running and still saw bubbles. Interestingly, when we hit small wakes at high speed the amount of bubbles in the strainer increased dramatically! Cutwaters have a step hull which entrains air under the hull for better performance. It obviously allows the raw water intake to suck air too!! Not sure what can be done about it.

 

[bill46]

Finally solved.
Checked exhaust injection, clear.
No bubbles in strainer.
Left raw water wash down disconnected, never used.
Had water and oil heat exchangers rodded out again, some crud found.
Seems Ok now. 196 WOT, 185 at 90%.
Thanks for all the ideas.
Bill

 

[Georgevb]

Read lots of good information on this subject above.

For those of you with multi port strainers, this may help.

The water line going from the multiport strainer to the toilet should have an inline one-way valve about 20 inch's past where it connects to the to the strainer. Check it to make sure it is not stuck open allowing water to go back towards the strainer. it so, replace the valve.

Also, for the wash down, install a one-way inline valve between the strainer line and the washdown pump.

hope this helps

 

[Gin]

Bill46: Interested in this issuein case I ever run into it (which, fingers crossed, I haven’t). Seems you downdrafts the solution but I can’t tell from your post exactly what it was. Mind clarifying?