From: gerard@progress.COM (Gerard Bras)
Newsgroups: rec.boats
Subject: Re: Overheating problem
Date: 8 Sep 92 20:22:18 GMT
Distribution: usa
Organization: Progress Software Corp.

jfh@cs.brown.edu (John F. Hughes) writes:

>I have a problem. Perhaps describing it as an overheating problem is
>prejudicial, so let me just describe the circs:

>We left Nantucket with a following breeze which died to nothing about 5 miles
>from our mooring, so we fired up the engine, a Westerbeke 4-107 diesel with
>fresh-water cooling. After running it for a little while, I heard the pump for
>the house fresh water (i.e., drinking water) come on. "Funny," I thought, "No
>one has used the taps..." but then the pump shut off again. "Hmmm. I suppose
>that a little pressure has just flowed out from the pipes, or perhaps they've
>warmed up and expanded a tiny bit in the engine compartment, and the pressure
>dropped below 40 lbs/sq in, so the pump triggered," I thought to myself.

>   During this time, then engine temperature had risen to about 185-190 on the
>meter. A little high, but within reason. I'd checked the oil, xmission oil, and
>cooling water before setting out, so I knew that things were generally OK.
>Aside from a very slow drip in one of my fuel feed lines--I think I need new
>washers--everything with the engine's been going pretty well recently. 

>   Anyhow, soon the drinking water pump cycled on and off again, and I went
>below to look around. Sure enough, the hot water heat exchanger (which heats the
>drinking water using hot engine water) had a slow drip at the forward end. 
>Bummer. I practiced the sailor's mantra: "What the hell, it's only money." 
>Turned off the power to the drinking water supply, and added an item to my 
>Do List.

The question arises whether the two are related.  I've never heard of these 
exchange type hot water heaters causing an outright blockage of the engine
coolant circuit.  Could happen though and should be easy to check.  Just
hook it up to a hose and let 'er rip.  Except that I always get suspicious about
coincidences I doubt it's related though.

>   Back on deck, I looked at the temp gauge, and it was saying something closer 
>to 200. That's a bit high, and I started to worry. But we w're nearly at the
>mooring, so I just ran on in. I figured "Next time we go out, I'll have some
>tinkering to do before we leave."

>   So the next time comes. I remove the drinking water heat exchanger, and take 
>the two hoses from the engine and join them with an elbow, and do the same 
>with the two hoses from the drinking water system. No more cycling water pump, 
>so the drinking water side is all happy (except that I happen to need a new 
>pump, too, since the old one it rapidly dying, and is held together with 
>bubblegum and prayer with hopes of lasting through the season. 

It's worth figuring out what was leaking before you throw money at the problem.
If the unit is rusted out then just chuck it.  If the tanks and coils are OK
I'd make an effort to fix it.  It may be as trivial as a plumbing fitting 
thats weeping.
 
>   During the removal of the exchanger, I lose lots of antifreeze from the
>hoses, so I top up the expansion tank, and fire up the engine to see how things
>work. Well, my wife's in the cockpit, watching the temp gauge, and it goes up
>to 180 (the thermostat's nominal setting) and then beyond. I've got the cap of
>the expansion tank off, and I've poured in a little more antifreeze and the
>bubbles work their way out of the system, but when the temp gauge says 210, I
>tell her to shut it down, and I swear a little. "What the hell is going on?," I
>ask. "Perhaps a bad thermostat?" I reach back and put my hand on the engine
>raw/fresh water heat exchanger, and it's cool to the touch. Warmer than the
>seawater by a little bit, but basically cool. With the engine water temp at
>210? Wha???

OK, this brings back some sad memories.  It's important that your expansion
tank be at the highest point in your cooling loop, otherwise you will never
get the air out and it will overheat, even though everything is topped off
and fine.  Try to figure out whether your engine is really overheating or
not.  Go to an auto parts place and get a calibrated gauge and screw
it into your block in place of the regular sender.  It will cost a couple
of bucks, but what the hell, it's only money after all.  If you are on the
right side of a mechanic you may be able to borrow one.

If it is overheating then you'll have to chase down why.  There are really 
three causes.

1) Lack of raw water flow to the heat exchanger.  You mention below that your
exchanger stays cool so this is probably not the problem by itself.  A quick
peek over the transom will tell you whether you have flow.  If not you
should not operate your engine until it's fixed as uour exhaust system
probably is not designed to handle uncooled gases.  If it's like mine
you're using rubber hose and there is a fire hazard.

2) Lack of fresh water (antifreeze solution) circulation.  While you
have the thermostat off, crank the engine.  If water spews all over your
boat it's fine.  Otherwise suspect a blocked/collapsed hose.  The water
pumps on the Westerbekes use a metal impeller and rarely fail, although
this cannot be ruled out.  As mentioned above trapped air can cause 
overheating which is vexedly hard to diagnose.  

3) Low compression.  You'd know by the hard starting and in advanced cases
a voluminous smoke trail.  An overheating engine will also smoke retchedly,
this is a real warning sign of trouble.

4) A defective guage.  Don't assume this until it's proven.  Them mills are
wicked expensive to replace.

My guess is 4 and/or 2.  BTW, before you removed it was the hot water heater
making hot water?  If so you were getting circulation at least at that point.

>   I let her cool down for half an hour, and try it again. This time the temp
>rises to about 200-205 and steadies off. I figure I've got more things to worry
>about, so we cool off and use the startup time on the thrid start to putter
>back out to our mooring. It's 10 PM, so it's about time for bed, whether the
>engine's overheating or not. 

>   Next morning, I get up, filled with energy, and swap in a new thermostat.
>It's not hard work, and aside form getting a little permatex on my hands, it
>goes well. Stove alcohol cleans up the permatex, and I'm ready to try the
>engine. We fire it up, let it run, and...the temperature gauge rises to 210
>again. But...the heat exchanger is still cool...I'm baffled. I remove the cover
>from the expansion tank, holding it in a terrycloth towel, and wearing an oven
>mitt, expecting lots of pressure and steam, and all I get is a little steam
>rising from the hole...no pressure to speak of at all. The tank's got plenty of
>fluid, and I figure "Maybe it's actually the temperature gauge. Perhaps 
>*it*'s what's giving me the grief."

You mentioned replacing the HWH with an elbow.  Why not put a calibration 
thermometer against the (metal?) elbow.  The little meat thermometer like
devices are available for a dollar three eighty at any auto parts place.
If it shows an abnormally high temp. then you are circulating overheated
coolant.  If it reads low then you have a blockage.  If it reads just right
you can relax and repair the guage.

>   So I crawl back into the seatlocker to look at the backside of the gauge,
>and one of the nuts that hold the wires to it is a little loose. Not really
>loose, but not tight either--I can loosen it with my hand. So I get my wrench
>and tighten it up, figuring that I've found the problem, and all will be well.
>I check the screw on the connection at the temperature gauge sender as
>well---it's nice and tight, and there's no trace of looseness in the 
>wire-terminal joint either. Looks good. 

>   We eat breakfast, and an hour and a half later, I get to trying the engine
>again. By now the engine block is cool to the touch--certainly no more than
>about 90 degrees. When I fire it up, the temp gauge reads 60 degrees for a
>moment, then jumps up to about 80, and then jumps (all this within about 15
>seconds) to about 140. As it rises, the needle makes sudden excursions to temps
>that around about 25 degrees lower than its farily steady (but rising)
>readings. The it settles in at about 200. Still, the heat exchanger is cool,
>and there's no pressure in the expansion tank. So I figure "What the hell, it
>*seems* OK even if that *is* too high a reading," and we take off (under sail).
>The two times we have to use the engine that weekend, the same thing happens:
>temps from 200 to 220, but no pressure in the exp. tank, and the heat exchanger
>only moderately warm.

>   Any conjectures? I'll probably just *remove* the t'stat for the next time I
>use her---that'll make her run at about 140 (or it did the last time), and
>that's no great sin. I'll probably only put an hour or two more on the engine 
>before haulout anyhow. But if anyone has ideas about what might be causing the
>high temperature readings, I'd love to hear them. Powerboaters: this is your
>chance to explain things to an ignorant sailor...I'm all ears.

From the sound of it all it doesn't sound like your engine is really getting 
all that hot.  Does it seem hotter than usual in the engine compartment?
Here's a guess.  The guage may be defective but more likely it's the sender
or the wiring  It really isn't usual for engine temp to bounce around a lot
so wiring is a real possibility.  You can test this stuff with even a cheap
Volt/Ohm meter.  The sender is basiscally a heat sensitive resistor and
the guage juast measures the current in the circuit.  The manual may tell
you what reasonable values are.  You can test the sender by putting it
in a pan of water with a calibration thermometer and heating it.  The
resistamce should change in a smooth and reasonably linear fashion.

You can run the engine without the thermostat but that may not fix the problem.
It's also not the best thing for the mill since it's really designed to 
operate around 180.  So other than a stopgap measure it's not worth it.

best of luck,
gerard
From: bsmith@hplvec.LVLD.HP.COM (Brian Smith)
Date: Wed, 9 Sep 1992 18:38:01 GMT
Subject: Re: Andrew in Miami
Organization: Hewlett-Packard Co., Loveland, CO