Ever-Popular Overheating Perkins 4108

[Chief Engineer]

Chiefs' Tip du jour.

When using an infrared sensor tool. Just don't aim it at the temp sensor.

Measure the following

Raw Water at thru-hull
Raw Water leaving Heat Exchanger
Fresh water from block to heat exchanger
Fresh water from Heat Exchanger to Block

This will give you a temp differential.
And will definitely tell you if you have an overheating problem or a gauge problem

[Archipelago]

Okay, Have to chime in. Had a 4.107 that had reliably overheated for the PO and me for many years. The heat exchanger had been cleaned so many time that it was probably tissue-thin. The water pumps had been overhauled so many times the bolts had to be renewed. No thermostat; it had been removed before I bought the boat. The problem turned out to be..... the exhaust elbow, where the water injection port had restricted to the point where it was barely pissing into the exhaust line. It was a wonder that the hose hadn't melted. I replaced the elbow with a 4.236 elbow (and yes, it fit). Wow! The engine ran so cold I had to reinstall a thermostat just to get the coolant into the lower end of the normal operating range. It's obscure, but if you are overheating CHECK YOUR EXHAUST INJECTION PORT!

David

[btrayfors]

David,

IMHO, you should have seen this much earlier.

It's good practice with ANY engine to look over the side of the boat at the exhaust and see how much water is flowing. Admitedly, if you're not familiar with the engine this can be very subjective, but on your own boat if you do this EVERY TIME you start the engine -- which you should do -- you'll notice a reduced water flow. And, of course, this will help to tell you if you have other problems as well, like a faulty impeller or a clog in the seawater intake filter.

Bill

[Archipelago]

Um thanks, Bill; it was a new boat (to me) and appeared to have some water flow out the exhaust (and yes, I did look). Certainly about what I'd had with smaller engines. Now I know better, but.... for those who are new to their boats, or have a long-running issue, it's worth a look. This also had been overlooked by at least two mechanics.

David

[jlogan]

Just a FINAL ending to the story. Called Sherri at TA diesels, explained my problem with new guage reading high, she said I must have gotten the wrong guage/sensor shipped to me. I finally got around to replacing the gauge they originally sent with the new one (and boy, did I do a good job of caulking when installing the original mismatched gauge). End result, after much work and replacing most cooling parts of engine, I now have a guage that runs at 170-180 at cruise, which is what temperature it actually was all the time I was "fixing the problem". Lesson learned: Buy a cheap infrared temperature device, calibrate it against a pot of boiling water or other thermometer to give yourself piece of mind that it is calibrated correctly, and use it to make sure you really have an overheating problem before "fixing" what doesn't exist. Besides, it is fun to point it at things and see what temperature things are and perhaps find problems before they become more serious (did you know that as you approach the time to change fluid in some transmissions they begin running hotter on the old oil.......)

THanks to all for all the help along the way and I think we all learned something, which is what makes this board so great...that and that we are all cheap and dedicated to keeping those old Perkins running.