Cummins Thermostat location.

Alright. I have been around engines my entire life. I could always locate a thermostat within seconds. I do know where the coolant goes back into the block from the heat exchanger, but it just appears to be a pip that goes straight into the block....with no housing!!!!!! Now I know that is where it is...that is where it has to be. But in all of my experiences, there has always been an obvious housing associated with a thermostat. I see none here. I am sure it is in there somewhere because it has to seat. But dammit!!! And does it require you to remove the alternator to get to it???

Anyway, in the past, the two easiest things to perform on a boat were the impeller and the thermostat. With a Cummins, that is not the case!!!

I am still chasing a heat issue on the left engine. I have done a bunch of stuff that needed to be down(impeller condition, aftercooler service, radiator flush and replace coolant, and I have even got after the engine with an IR gun to confirm gauge operation). Now before I hire out someone to nip this thing in the bud, I figured that changing the thermostat would be easy(and cheap) enough to check that off the list of offenders. I am not sure how easy it is though. The only thing I have left is the thermostat, oil cooler,heat exchanger, and finally the exhaust elbow...in order of expense.

While I started this thread about thermostat location, I would gladly listen to y'all as it relates to my heat problem. I use the word "heat" instead of overheat. It is not overheating. It has been a steady creep. And now under normal cruise load(2300rpm and 17 knots), It is getting close to 200....every bit of 195). With that said, it has been somewhat random. Sometimes it will not do it. Sometimes it will. I just made a 450 mile journey in early October and it performed perfectly the whole time. But it was still 185ish...188ish. Just hotter than it used to be and definitely hotter than the right side. ANd now even hotter. SO the "randomness" of the occurence could be a symptom of a sticky thermostat. I do know that thermostats generally do NOT cause heating issues...but it is just so easy and cheap to cross off the list.

Next step would be hiring the local Cummins guy to take a boat ride and shoot differential readings along the cooling system.

Also, my boat is severely underpropped(Almost 3100rpm on a 2800rpm engine). So it is not overloaded. The boat has been dove on...and it has been quickhauled...nothing to note. Strainers are clean. No collapsed hoses under load. Water flow APPEARS to be normal....but who knows.

Thanks...I thought this was gonna be a short post...hahaha!!!

What Cummins engine?

You might have 2 thermostats, my 8.3 does.

Cummins are very picky about coolant. Have you checked the additive package? Have you changed your coolant this century? Have you changed the coolant filter? As soon as I changed the coolant in my engine the over-heating issue I had went away. The filters (I don't know if they all do, but Fleetguard does) contain the additives needed for the coolant but eventually you have to change it anyway. Try this before you throw parts at it.

Have you run Rydlyme or Barnacle Buster through the HE with a pump and a bucket yet? I followed Flyright's method on my engine and it helped. Got a lot of fizzing and gunk out of the HE and my temps are down now.

Xsbank said:

What Cummins engine?

You might have 2 thermostats, my 8.3 does.

Cummins are very picky about coolant. Have you checked the additive package? Have you changed your coolant this century? Have you changed the coolant filter? As soon as I changed the coolant in my engine the over-heating issue I had went away. The filters (I don't know if they all do, but Fleetguard does) contain the additives needed for the coolant but eventually you have to change it anyway. Try this before you throw parts at it.

Click to expand...

Ok...coolant filter? That is a new one. And it is a 6BTA. 330hp. 2001 vintage.

Your BTA 330 is not fitted with a coolant filter as standard, The thermostat is located behind the alternator mount bracket...

Gurryman said:

Your BTA 330 is not fitted with a coolant filter as standard, The thermostat is located behind the alternator mount bracket...

Click to expand...

I will take another look at it today....Does it require taking the alternator off to replace the thermostat???

Baker said:

I will take another look at it today....Does it require taking the alternator off to replace the thermostat???

Click to expand...

That depends on your installation. You can usually swing the alt out on the lower bracket, It you have a hard pipe from the T-stat to the heat exchanger
you may need to remove the header tank bolts to get the pipe off. The Cummins B series T-stat seals with a square o-ring and No Gasket, so you need a little room to ensure the O-ring seats correctly.

Coolant?

Xsbank said:

Coolant?

Click to expand...

If you are asking what type....It is Fleetguard Compleat. Made by Cummins. Blue stuff!!!

We just came due for our periodic antifreeze replacement. Drain. Flush with Fleetguard Restore. Drain. Flush with fresh water. Drain. Install new coolant filters. Refill with 50/50 Fleetguard Compleat. Kind of a cumbersone project, but not particularly difficult.


Absolutely no change in coolant temps. Gotta do it, though, per service manual.


-Chris

Erratic temps are often caused by some junk in the tranny cooler or other location blocking flow sometimes and sometimes not. Especially impeller pieces.

bayview said:

Erratic temps are often caused by some junk in the tranny cooler or other location blocking flow sometimes and sometimes not. Especially impeller pieces.

Click to expand...

Makes sense. I do not think the left engine has ever shed an impeller though. And if it did, it would never make it any further than theafter cooler...that is the first stop after the water pump.

The after cooler will indeed stop stuff. Mechanics are know for not bothering to chase down missing impeller pieces so unless you did all the work since new I would start there.

I have the same motor.
Just FYI the stock cummins thermostat is rated to 200 degrees, so I wouldnt be too alarmed at that temperature (yet). I completely disassembled and cleaned or replaced all the components on my cooling system. By far the biggest offender was the transmission cooler. It was 90% clogged. Much worse than the intercooler. In fact, I replaced that and the heat exchanger as well. I had the old heat exchanger cleaned, rebuilt and tested and I have it as a spare in my garage if necessary. If you have not fully serviced your cooling system on your motors in the last 5 years, do it. Check the HX and especially the tranny cooler.

Oh, and the thermostat is under the alternator.

I should also note that after I serviced everything, I still had temperature fluctuations until I flushed the coolant several times and replaced the thermostat as there was crud in the thermostat and antifreeze side of the cooling system preventing it from opening and closing properly. Everything has been great now for the last year plus.

bligh said:

I have the same motor.
Just FYI the stock cummins thermostat is rated to 200 degrees, so I wouldnt be too alarmed at that temperature (yet). I completely disassembled and cleaned or replaced all the components on my cooling system. By far the biggest offender was the transmission cooler. It was 90% clogged. Much worse than the intercooler. In fact, I replaced that and the heat exchanger as well. I had the old heat exchanger cleaned, rebuilt and tested and I have it as a spare in my garage if necessary. If you have not fully serviced your cooling system on your motors in the last 5 years, do it. Check the HX and especially the tranny cooler.

Click to expand...

Thank you sir....the tranny cooler has not been serviced/replaced. So I will take a look at it. A 200 degree thermostat might be a holdover for over the road applications??? I know applications like Dodge Ram trucks struggle to keep temps up due to being underloaded the vast majority of their lives. But Boats, planing boats in particular, don't have that issue. Anyway, I will take a look. There does not appear to be a flow problem, but that is hard to quantify...especially if there are bypasses anywhere.

If this is new to you I suggest getting the proper Cummins manual and parts list books for your exact CPL. They are well done and very helpful.

Baker said:

Thank you sir....the tranny cooler has not been serviced/replaced. So I will take a look at it. A 200 degree thermostat might be a holdover for over the road applications??? I know applications like Dodge Ram trucks struggle to keep temps up due to being underloaded the vast majority of their lives. But Boats, planing boats in particular, don't have that issue. Anyway, I will take a look. There does not appear to be a flow problem, but that is hard to quantify...especially if there are bypasses anywhere.

Click to expand...

i ordered the thermostat from seaboard marine who used my serial number to get the thermostat. and I asked them about the temperature range and that was what they told me which was also in agreement with my Cummins manual that came with the engine/boat. My engine is a 1999 or 98. Max engine temperature operating range is 203 F according to the manual.

I am still battling this. But the battle is less serious right now as water temps are quite cool. I do not know if that would have anything to do with it. In theory, it should not. I did get a Cummins guy to ride along with me to shoot temps. His temp samples were primarily of where the coolant comes out of the block at the thermostat....the actual metal hose that comes off of the thermostat. And at that location, the temp was...wait for it....180 degrees!! Ironically, in the same location, the temp on the right engine was about 185.

Anyway, would this be a proper place to measure temperature for this issue??? I am still not feeling all warm and fuzzy about this. Basically, we accomplished nothing except we now know the temps coming out of the engine are 180. Should I just shrug it off as a gauge problem.....

Baker said:

Should I just shrug it off as a gauge problem.....

Click to expand...

Have all your previous temperature "measurements" -- prior to the Cummins guy shooting them -- come from eyeballing your gauges?

If so, what gauges? And what senders?

When I was changing to new digital temp gauges -- our original Faria gauges always gave very consistent but very incorrect readings -- I discovered part of the reason was because the senders and the gauges were incompatible. Our engines are apparently always delivered with VDO senders, our boat maker should have switched those out to Teleflex if they wanted them to work with Faria gauges... but they apparently forgot that minor detail.

That probably wouldn't account for a "temps used to read correctly, right but now they're not right" situation, though...

But I'm guessing gauges, and maybe senders, can fail...

-Chris

ranger42c said:

Have all your previous temperature "measurements" -- prior to the Cummins guy shooting them -- come from eyeballing your gauges?

If so, what gauges? And what senders?

When I was changing to new digital temp gauges -- our original Faria gauges always gave very consistent but very incorrect readings -- I discovered part of the reason was because the senders and the gauges were incompatible. Our engines are apparently always delivered with VDO senders, our boat maker should have switched those out to Teleflex if they wanted them to work with Faria gauges... but they apparently forgot that minor detail.

That probably wouldn't account for a "temps used to read correctly, right but now they're not right" situation, though...

But I'm guessing gauges, and maybe senders, can fail...

-Chris

Click to expand...

Gauges are OEM. And the issue is consistency. If this was consistent, and I had shot the temps and was happy about it and the gauges read consistently, I would have no problem. But it is not. When I purchased the boat, there was no issue. Now it has steadily crept up. And sometimes it is perfectly fine....but then the temp will jump up close to 200.

Baker said:

IAnyway, would this be a proper place to measure temperature for this issue??? I am still not feeling all warm and fuzzy about this. Basically, we accomplished nothing except we now know the temps coming out of the engine are 180. Should I just shrug it off as a gauge problem.....

Click to expand...

Where he measured is important...however I like to take readings right on the temp sender to compare with what the gage says.
And when I find that those two readings no longer agree (within reason) I change the gage and sender. That has always worked for me.

jleonard said:

Where he measured is important...however I like to take readings right on the temp sender to compare with what the gage says.
And when I find that those two readings no longer agree (within reason) I change the gage and sender. That has always worked for me.

Click to expand...

While I agree in theory, in reality, that is challenging. If you move one millimeter from the sender the temp changes 10...20...maybe even 100 degrees!!!! SO it is extremely difficult to get a consistent reading anywhere near the sender. I PMed Ski about this awhile back and he agreed with you and I tried. But I could not get a consistent reading. It appeared to agree with the gauge but it really depended on where I was shooting. One little mm shift in position and the temp would shoot up to 300+.....

If you are getting near the exhaust port, you will get high readings. Some guns have a wide angle and those are hard to use. Or you may be too far away and gun senses the hottest thing in view, may need to get closer. On the B's, I shoot near the temp sender right above thermostat. If hard to get to, I shoot the metal section of the outlet tube going from tstat to HX. Usually those two points are with 5F of each other. You can't get a good reading on rubber hose.

John, As you may recall, I chased a perceived engine heating problem on my Halvorsen single engine trawler for quite some time. (330B) It was running at 192 degrees (the guage on the panel reading) & I was convinced that was too hot. You name it, I changed everything you can change that has anything to do with the 330B cooling system. (ie: coolant, heat exchangers rodded, thermostat, sender, guage at the panel, etc.) I bought an IR gun to check the locations recommended by Tony Athens at Boat Diesel.com. (Best $25 I ever spent!) The long & short of my problem is this....that engine ran at 192 degrees all the time! It ran at that temperature with no problems right up and until I sold it!

Here's a photo from SeaBoard Marine (Tony Athen's outfit) that was linked to me. It also shows the location of the thermostat.

IR Gun Temperature Check - Seaboard Marine

Ski in NC said:

I shoot the metal section of the outlet tube going from tstat to HX. Usually those two points are with 5F of each other. You can't get a good reading on rubber hose.

Click to expand...

That is where he was shooting and where I will shoot from now on. It was dead on the money 180. Now realize this was with the gauge reading about 185 instead of the near 195 temps I have been seeing. So I will just keep watching it. When I see a reading of 195 I will run down and take a shot of it. It is fairly easy to get to so it wouldn't be hard to get a shot while randomly underway.

Intermittent overheat can be due to impeller pieces in FRONT of the pump, between the strainer and the pump.
It doesn't sound rational that they would be in that location, but is often the case.
When a blade lets go, the remaining blades will push the loose pieces into any available orifice, inlet or outlet.
Seaboard has a 165 degree thermostat if that fits your need better.
You can find interesting discussion of the topic on boatdiesel.com.

Greetings,
The mention of differing temperatures (within mm of a particular location) whilst "shooting" with an IR gun reminds me I should get some stick on black dots.
During her ER checks, the Admiral, shoots and records temps at several locations. I've been meaning to buy some above mentioned black dots and apply them to strategic locations on the engines so as to compare readings from the same spots every time. Similar to...

600 BLACK 1/4" map stick-on map dots

RT Firefly said:

Greetings,
The mention of differing temperatures (within mm of a particular location) whilst "shooting" with an IR gun reminds me I should get some stick on black dots.
During her ER checks, the Admiral, shoots and records temps at several locations. I've been meaning to buy some above mentioned black dots and apply them to strategic locations on the engines so as to compare readings from the same spots every time. Similar to...

600 BLACK 1/4" map stick-on map dots

Click to expand...

We call them "paper a s s h o l e s"....