Adding new Temp Sensors Lehman 120

[rebuckley]

So my rebuild of the entire cooling system is complete on the Lehman 120. All new hoses (American Diesel hose kit), new thermometer and gasket for the expansion tank (American Diesel) new oil coolers w/zinc (Mr. Cool) and new Heat Exchanger (Mr. Cool) - and BW Transmission rebuilt.
Sea Trial yesterday - temp gauges not giving anything (I think the sender they are paired with is wrong). But used an IR gun to measure along the engine/cooling system. Temps were all great all along the system - the exchanger had a 20 degree variance from hot to cold ends (real efficient).
One issue came up - when running around 2K RPM - the mixing elbow started getting warmer - mate didn't record the temp - but it was rising. Kicked back 200 or 300 RPM and it came right back down.
I think the elbow needs replacing, and that is on my spring "to-do" list - but is there anything else I should be looking at that may be casing the heat issue at the elbow? The manifold stayed cool - around 130 or so - but the elbow had a spike?

[jleonard]

Good deal, engine looks great.
Yes more than likely the elbow needs replacing. Any idea how old it is?

[rebuckley]

Thanks Jay -

Not a clue - but when I had the HE off, I noticed a little rust on the bottom of the elbow - so I determined at that point to replace it in the spring. I think once I get winterization done, I will pull it off (or begin to try) and hope the bolts are cooperative.

[RobS]

Reb, how "warm" did the exhaust mixer get? Wet exhaust temps can approach 140deg F or so.
FWIW, the Borel wet exhaust temperature bands close and set off the alarm at 167deg F...

[rebuckley]

Thx Rob, that is the question, the only response was it was getting warm...I need to try again, but will replace proactively. I am just assuming it is the elbow, because the person running the ir temps said the manifold was fine

[kerrye]

Do you know what the normal temperature of the mixing elbow is at that rpm? Seems it would get hot quicker than the manifold since it has much less mass than the manifold. What would a new mixing elbow do to get lower temperatures? Could it be that water is being held back in the exhaust pipe at higher rates of flow causing the elbow temperature to increase? Is the exhaust pipe itself also getting hotter?

[brookesmith]

I just replaced my elbow. Brian at ADC said the bottom of the elbow runs very hot. I believe I measured 700°.. Paint will not stay on the lower part of the elbow. Be prepared to change the exhaust elbow hose too. The raw water only enters the top of the elbow. So, the bottom near the manifold runs really hot. I just replaced the elbow (5080 hrs) A PO must have changed one prior and there was damage to the exhaust manifold. A longer bolt had been used on one bolt. CAUTION WHEN CHANGING THE ELBOW. You need to drain the manifold (somehow) or antifreeze water will end up in a cylinder. Anyhow, mine is changed and some water got in the back cylinder area of the manifold but the valve was closed and a turkey baster and some rags got it out. Brian has a nice elbow kit. Just make sure you drain the manifold before you take the old elbow off. I believe you can drain the heat exchanger to lower the water level in the manifold. Check with Brian or some other expert.

[rebuckley]

Millard -
That is great information - thank you - I id not even think about draining the manifold...so I will make sure to do so prior to making my change. I did see the kit on AD, that was where I intended to buy it from.