210 Cummins 6B temp limits?

[WaterLover]

This past week, I learned how to change out both raw water impellers. The old ones actually looked pretty good but since the parts were opened up and I had 4 as new spare parts on board, I changed them out for new. Water seems to be flowing well and alternators and belts are good (less than 6 months old each). I don't think the problem has to do with raw water flow.

I have an IR gun and ran the engines for a while this weekend and then up to WOT. I got 2800 rpm at WOT for both engines, however the port engine at this time read only 170 degrees and the starboard was up around 205 degrees. I was in the engine room shooting it with the gun to check temps and while the starboard was hotter than the port engine I never got a reading over 200 in the gun (although I really am not sure I was shooting the right part of the engine). Any hints on which parts I should hit? Even while warming up the engines at 1200 rpm the temp gauge for the starboard engine was inching very close to 200 degrees while the port was no where near that level. So it looks like number 1-4 above are not the problem. I guess next up will be the heat exchanger.

I have been told that you can take them off and take them to a radiator service place to be "baked" in order to get rid of any buildup that may be hindering internal water flow. Do you all agree?

Thanks again everyone for the very helpful suggestions.
Capt. Annie

[bccanucker]

Yes, a radiator shop is where to take it. I've never heard the work "baked" associated with this. My rad shop "cleans" them which means they clean out all the round holes that run through the heat exchanger. The more salt water that can flow through the cooler your engine water gets.

[jleonard]

Any hints on which parts I should hit?

You should take the readings at the temperature sending unit if possible.

You can clean the heat exchanger yourself. Simply flush it out with water from your garden hose after you remove the two endcaps to start off. Then inspect each tube to see if it is clear. If there are obstructions you can use a brazing rod or a .22 caliber rifle cleaning brush to remove the debris. Then flush again.

You can (and should) do the same with the tranny coolers to make sure there are no issues stopping or slowing down the water flow.

Water seems to be flowing well

is a good quick check but it doesn't mean that you DO have enough water flowing. I have been there before.

[mike66]

I'm a little confused.. did your readings at WOT come from the temp gauge or the IR gun? If you aim your gun at the coolant tank where the filler cap is and the sending gauge usually is, you'll have a good idea of your engine temp. Also good to compare the temp of the exhaust manifolds and hoses one engine to the other - this would give you a rough idea of coolant flow through the engine. 200 at WOT is not too bad if it goes back to 170 - 80 at cruise. A weak cooling system, but not a dire emergency. And yes, follow the above post as far as cleaning. The thing a shop might do for you is pressure test the exchangers as well as clean them if the problem continues.

[WaterLover]

As an update. At the suggestion of a Cummins Marine test engineer (my ex) I ran an engine test while at the dock. I ran both engines from cold start up and "shot" each coolant tank with my IR gun every minute until an engine either reached over 200 degrees (with IR gun) or stopped gaining temp (recorded in an excel spreadsheet). This happened after about 40 mins (a little extra time just to be sure). I was unable to get the engine to get to 200 this time (at the lower helm gauge or with the IR gun) even once I bumped the RMP up to 2200 for a few more minutes (I periodically checked the gauges to compare to the temp readings during the test).

I sent the results back to the engineer and asked for his opinion. He says that the temp curves looked normal in both engines. And told me that my gauges are regularly running 10 degrees higher than the actual engine temps (confirmed with IR temp gun-this is good to know as I can't often get down there to check them while underway). He said this is also very usual (normal). He concludes that since this issue is intermittent, and that it happens even while NOT under load he is 90% sure it is my thermostat that is sticking. He says that they test these engines for long term running at 220 regularly (stress tests) and that running up to 220 will not cause long term engine damage. Anything over ~230 could do damage. He also told me that if it were the heat exchanger I would only see the overheating happen while under load.

The good news is the thermostat replacement part can be bought for $15...the bad news is that my particular engine (this was only true for 2 years) does not "fit" the new thermostat well. The area the thermostat goes in is too small for the replacement part and thus the cylinder head must be ground out for a new one to fit correctly making a 30min job, a two hour job and probably requiring a knowledgeable Cummins technician which will raise the price of the fix a good amount.

I have learned a lot and that is good. Also, the problem is not so bad right now that I can't continue weekend cruised for the next couple of months. I plan to have it taken care of when I have the boat hauled for bottom paint this winter.

Thanks to all for your interest in this topic,
Capt. Annie

P.S.- I also learned not to wait 2 months to ask my ex for advice since he is an expert on these engines (even if I don't want too:)

[jleonard]

I happen to have in my posession an thermostat housing and thermostat for a mid 80s Cummins 6BT 210.
The thermostat large OD is 2.125 (2 1/8)". Around the body is a black rubber ring that looks like it's bonded to the thermostat base. Numbers printed on that rubber piece is 31(33) 589. (Numbers in parenthesis I am not sure of). Part of the assembly is a seperate rubber donut with part no. 3923331 KD with an arrow pointing to the small od end goingtoward the thermostat.
I just boiled the T stat and it doesn't open.

If you might be interested in that housing let me know. It needs to be wire brushed and painted. Make me an offer I can't refuse.

trying to get rid of all my Cummins parts. I also have 2 exhaust manifolds, a raw water pump (good only for a rebuild) and an exhaust wet elbow (for 4 inch hose).

[mike66]

Glad you're not facing major problems. And acquisition of an IR gun was a good thing. And practicing changing out those impellers. I'm wondering, would it be best to test that thermostat before going through all the expense of replacing it? That is, if it is removable without all that labor you mentioned. I couldn't tell by your post if access is a problem, or the replacement parts are the problem. Sorry if I'm stating the obvious.

[WaterLover]

Hi Mike (or Sue),
I have had an IR gun for a long time so I agree it helped once I found out what to point it at:) The problem is an ill-fitting replacement part (i.e. the new part is now bigger than the old and no older ones are made any longer). I am sure I could take it out and do a boil test. However, we think that it may be sticking because someone has replaced it in the past but did not hollow out the head appropriately for the size differential and that is why it is not working well. Thus, it may work outside of the engine fine and not so well in the space without the added grinding of the cylinder.

jleonard, I am considering taking you up on your great parts offer. It has actually made me think about searching for an older thermometer on the web...
-Annie

[mike66]

Thanks. That makes things pretty clear, even for me. (Mike) . Good luck in your search for a new/oldstyle one.

[WaterLover]

Ahhh, the plot thickens, we now think there is a new retrofit part that does not require the grinding (Cummins part 3802968). Will update once it is installed mid Nov (have a weekend cruise that I must go on first prior to tearing at the engine again...priorities you know:).
-Annie

[jleonard]

You could also look into a thermostat for a Cummins 6BT that is in a pick up truck. I have been in Dodge-Cummins truck forums for years and do not recall lever hearing that a T stat housing had to be ground out. I know there is a rubber donut that allows a smaller dia T stat to fit, but never heard of your scenario.

[C lectric]

Do not start grinding. Although not a Cummins 210 expert this sounds absolutely haywire. When you purchased the stats did you have the
CPL number
and
the serial number

They are on a tag on the side of the gear cover , front of the engine, when facing the engine on the R.H. side near the top.
Even if one engine is missing its tag you really only need one to get set as they both will have been installed and purchased at the same time, hopefully. Best if you have both engines' numbers.

In truth either the CPL or Ser should be enough but having both is best. There have been changes over the years and without those numbers someone may have guessed wrong.
All machinery undergoes changes and without those numbers you are asking for trouble. There can be construction changes in the same year, with the same model and horsepower number.
Good luck

[WaterLover]

No worries, I have this info from a Cummins test engineer for these engines (based on the CPL and tag numbers) but I don't think I will have to grind now that we have found a better solution.

[WaterLover]

Quick update: Engines are running great with no problems.