Running Cold

[Tom Graham]

This A4 is in a C&C 27 on Lake Champlain where the water can be as cold as 45 degrees at launch time and at most 70 in the summer. I have had the boat for 4 seasons and done a lot of engine maintenance including rebuilding the water pump and installing the Moyer low cost thermostat and spacer. Unless you push the engine so that boat is trying to go beyond hull speed, probably about 2000RPM the temp gage hardly moves.

The water pump kit included a new "shoe?" to increase flow. I installed this and possibly it was after that that the running cold situaiton started. I did this change and others over the winter so I can't be sure.

Would the increased pump pressure and flow be causing water to bypass the thermostat? This is the only reason I can think of for this.

Should I go back the old pump set-up"" I am thinking of buying an entirely new pump and using the old one as a spare. Would the new one be highflow/pressure?

The engine runs fine, with Don's hotter plugs the plugs stay clean but around the edge there is some soot build-up.

Thanks

[rigspelt]

Are the temperature gauge/sender accurate/working?

[Tom Graham]

Sender and Gage OK

Yes both of these seem to be OK I have confirmed using a Thermocouple.

Tom G.
"Monk"

[rigspelt]

Nothing funny about the way the sender sits in its seat in the head? Just wondering if it could be too far away from the hot water in there somehow, for example sitting in a bushing of some kind?

[Dromo]

Thermostat?

I would take the thermostat out and check it. It sounds like it's stuck open for some reason. Maybe test it in a pot of hot water on the stove, just to eliminate it as a cause of the problem
Rick
P.S I found some text regarding increased pump pressure that you might find interesting from Hessmarine FAQ.

[dvd]

Kind of heating up?

Not to change the subject but my A-4 has begun operating at about 180 during normal cruising speeds, but smetimes will creep up to the 190s and then go back down. I can watch the guage start going up but it then starts to go back down fairly fast. A couple of times it was probably 195 which I do not like. Their seems to be a good amount of water coming out of the exhaust when this happens. I'm thinking new thermostat? New impeller or to be safe both. Also if I need a new thermostat do I purchase the moyer marine 140 degree. What temp should the engine be running? It does not have a sealed cooling system.

DVD

[High Hopes]

Tom,

I had a similar problem because everything was corroded and water passed around the housing port and the head seat. The new kit - and a new head and a new manifold (hopefully not your case) - fixed my problems. [It's a long story] But my initial problem sounds a lot like yours. I suspect you have a bad thermostat, as suggested here by others. Somehow, water keeps flowing through the block. It really doesn't matter how cold the intake water is, if the thermostat stays shut, the engine will heat up.

The boiling pot and a thermometer is a very good way to check thermostat operation. I also used this technique to test overtemp sensors and identified two bad ones this way.

dvd,

After I fixed my first A4 problem, described above, I had a problem like yours. The new problem was fixed with a new manifold ($) which was caked up big time. A new head ($) improved things further. There's nothing like money to fix things up. I still haven't figured out how I could have had both problems (too cold and too hot), but there you go. You would think they would have cancelled each other out. It works like a champ now.

S

[Tom Graham]

Running Cold - Update

Thanks for all the comments. The note attached to the response from "Dromo" seems to lend credit to my thinking about too high a pump pressure.

Regarding the comments re a bad thermostat perhaps I should add some more info.

I checked the original thermostat, an old 3 spring Holley and it worked OK.

However, not being sure of the age of the pump impeller I replaced it and installed the larger shim type devices that came with the kit, that produce a greater impeller deformation to give more flow and perhaps pressure, the two usually go together. I believe this is when it started to run cold.

The cyl head casting is in good condition and the Thermostat fits in its recess snugly and seems to seal fine. The housing was a little corroded however.

So I purchased the MOYER thermostat, the lower price one, the necessary spacer and special nuts plus the bronze housing. It still ran cold and that's where I am now.

Any others that migth agree with the idea of the higher pressure pump forcing the water past the Thermostat??

Thanks again,
Tom G.

[Don Moyer]

Tom,

Your situation is very perplexing. We usually say that "overcooling" can only be caused by water flowing through a partially stuck open thermostat, flowing around a closed thermostat if the head and/or base of the housing is corroded or the gauge is defective. I would also add that if there is any unusual restriction in the bypass loop, it can sometimes force water through even a normal thermostat and housing.

We really have no history to suggest that an M7 cam shoe leads to overcooling.

All that being said, it will be interesting to follow your case history to learn what is causing the overcooling.

Don

[Tom Graham]

Don,

Thanks for your reply. I note your comment about the bypass loop and will check it out. It will be another month before I start work on the boat and it does usually not go into the water until early May but will keep you posted.

I will likely be ordering a new pump and thermostat gaskets soon. I want to have a spare pump not just impeller it is easier to just change the whole pump out.

Thanks,
Tom G.

[marthur]

Been there...

I had a very similar problem with our A-4 (running on Lake Michigan, where the water is COLD in the spring).

My A-4 ran around 180 until I rebuilt my water pump. Then some funny things happened, the engine ran MUCH cooler (around 125) until one day it never warmed up at all.

It turned out that two things were going on, the first was a piece of water pump impeller from who knows how long ago was dislodged and partially blocked the by-pass. This helped a lot, but the engine still ran a little cool.

However, when I next adjusted the mixture and the timing the engine temperature came up to 140 degrees and has stayed there ever since.

[domagami]

Overcooling causes?

Hi;

We fret so much about overheating that we welcome a cool running engine - until that actually happens.

I've run hot, but I think I have resolved those issues. Last fall and yesterday I was running cold (`120) and I've been trying to sort that out. Always interested in any feedback others have on this so please post if you can comment.

Since my overcooling finished in a shutdown at the worst time possible (Chicago River, downtown, during a bridge raising with hundreds of cars waiting on you) I replaced a lot of parts just to eliminate them as a possible source.

I had a bad alternator - diodes fried probably. Could not recharge batteries so I had the alternator replaced. Two outings later I started running cold, that 120 I mentioned. I'm just in and out of the harbor, so my 'runs' are usually on the short side - but yes, I'm trying to run it longer as a rule. On the third outing I ran for 60-90 minutes before it failed. During the run it sounded... rough... almost like something was missing or clanging somewhere in the engine. (Yea, that was fun to hear)

After working on it for two hours following the shutdown (does this mean things were cooling off??) I got it restarted for 5 min, only to die again forever.

I restarted it last night in the water at idle, no load on the engine - even after 40 minutes it maxed out at .... 120.

I then replaced the points, condensor, dist. cap, coil, plugs, all wires, neg. lead from dist. to coil (maybe the true culprit was this one - the cheap fix), fuel filters, and tore the carb completely apart and cleaned it to death. Also adjusted the dist with the mounting bolt as best I can, and played with the idle set screw to smooth out the pace.

Two hours, above idle, in forward on the dock lines.... it comes right up to 180-190. Sound starting to smooth out.

Was it the neg. lead? Was it the coil? (Seems to maybe lead that direction given how it restarted after cooling for two hours.) I'll never know for sure, but it would be interesting to hear your comments.

Thanks to all.

Mick

[marthur]

It could be an ignition thing, but don't discount timing and mixture. Both of those can have a very large effect on operating temperature.

[Baltimore Sailor]

When you do that many things at once you'll never know what the problem really was. That's why I like to make one change at a time, to see when the trouble actually went away; however, I can see that there'd be times when you can't take the patient scientific approach.

At those times, just be happy you fixed the problem!

[JimG]

I'll be looking forward to your solution. My A4 won't move my gauge unless I close the raw water inlet. It runs fine, and starts reliably. It's raw water cooled (50 deg F year round).
When I bought the boat, the bypass had a restrictor installed, which I drilled out. I'm pretty sure the gauge is working, since I can put my hand on the block. I've stove-tested the thermostat several times.

I figure I'm getting poorer efficiency than I could, but it takes me a full year to go through one tankful, so it's no big deal...