Engine Overheated - Is it Ruined ?

[Maddog]

Also, if you turn the key off while running, you will also disconnect the excite wire to you alternator (If it is set up this way) and stop charging the batteries and possibly damaging the diodes. Good luck.

[FSMike]

Bright Eyes -
Before you crank up that poor engine again invest in a complete set of gauges.

[Mark Zarley]

I notice that the only alarm mentioned is for oil pressure. There are two eng temperature sending units on an eng. One is for the eng temp guage, the other is activated by high engine temperature and sets off a warning buzzer, simmilar to the low oil pressure buzzer or alarm.

[Bright Eyes]

Yeah that makes about the alarm being an oil pressure alarm. So I guess I should wait for it to turn off on its own after the pressure builds up correctly.

Last night I took out all the hosed related to the cooling system. They had alot of grime and some build up inside so they are all getting replaced.

I also took out the thermostat. The service manual recommended changing it every 2000 hours and our engine has 2200 so that will be replaced.

For right now I am just gonna get the engine operating again so we don't spend all summer in the slip. But once it is back in service I would like to add a oil pressure gauge, fuel pressure guage, fuel tank guage, and engine temperature gauge to my starter panel. That would be nice!

[Maddog]

Don't make the mistake of hooking the alarm up to the sending units used by the gauges. The alarm needs to have their own sending units. For oil its easy just use a "T" fitting off the block where the oil sending unit is attached. For the high temp water you need to locate a threaded port in the head and attach it there. If you double them up the gaiges will read wrong, (low, I belive) and the alarm won't sound when it should.

[cal40john]

Originally Posted by Mark Zarley

I notice that the only alarm mentioned is for oil pressure. There are two eng temperature sending units on an eng. One is for the eng temp guage, the other is activated by high engine temperature and sets off a warning buzzer, simmilar to the low oil pressure buzzer or alarm.

3GM30 without options has high temp engine buzzer and low oil buzzer switches. There are no temp gage or oil gage senders.

John

[Maddog]

That is backwards, akin to idiot lights in a car. Does that engine have the capacity to add the other other water temp sender? The oil should be easy.

[osirissail]

Most important among the list of items already listed for checking and replacement is to find all the little "vanes" that came off the raw water impeller when it self-destructed. The normal raw water path is from the sea strainer to the raw water pump and then up to a heat exchanger before eventually getting to the engine exhaust system.
- - The heat exchanger needs to be opened up and any broken off raw water impeller vanes removed. Each of the small tubes in the heat exchanger needs to be checked to be sure they are completely open and free of obstructions.
- - If the pipe/hoses from the raw water pump to the heat exchanger includes right angle bends or any sharp bend the hose needs to be removed and visually checked for blockages caused by parts/debris from the shredded raw water impeller.
- - Otherwise the engine will continue to overheat due to restricted raw water flow and/or obstructions blocking the heat exchanger tubes.

[MitchM]

Just a few more thoughts on the importance of cleaning the HEAT EXCHANGER :
it is important to completely remove the heat exchanger from the system and clean each tube with a pipe cleaner. . impeller pieces can travel downstream and if you are lucky they are trapped in the rear gear side part of the heat exchanger. if you a re unlucky the impeller pieces will trap tehmselves in one or more of the little tubes. think of the ht ex as a long metal tube filled with about 30 small pencil diameter tubes . shine a flashlight thru each little tube looking for a blockage of the light and to be safe ream out each tube individually with a small brush pipe-cleaner size. on our engine , we sucked a piece of 6 inch windshield wiper into the r raw water filter which is a manifold style with metal mesh cartridge. . the wiper piece reduced water flow enough to fry the impeller, but the water pump kept pumping at reduced flow. the impeller pieces traveled into the ht ex rear cover where a few of them stuck. at 2800 rpm the alarm went off and i idled it to a stop. in the middle of lake erie, i cleaned out those pieces, put in a new impeller, tested the thermostat OK and thought the job was done --WRONG. on engine startup, it idled fine but the alarm went off again at cruising speed 2800 rpms. back at the dock, took off the ht exh again (which required a #40 Torx wrench WHY?????) Well a small piece of impeller was lodged sideways in one of the tubes... clean and reassemble.. Lesson learned PLUS i now have a complete set of Torx wrenchs...

[SkiprJohn]

Is your engine running again?
kind regards

[osirissail]

If when you take the engine heat exchanger off the engine for cleaning you notice that the copper tubes that are used to attach the hoses - are eaten away a little, then you need to "pressure test" the heat exchanger.
- - U.S. made heat exchangers are either copper or cupro-nickel (the higher priced ones) and are made by soldering different size copper tubing together. There are short tubes soldered onto the body of the heat exchanger and are used to attach the various inlet and outlet hoses. When you remove the inlet and outlet hoses you may notice that some of the copper metal has been "eaten" away by electrolysis. If this is the case then you should "pressure test" the heat exchanger as it might just be that the interior tubes are also been eaten away to tissue thin condition. Rupture of the little tubes will allow raw sea water to mix with the clean fresh water coolant in your engine. If that happens the salt water will start to eat away at the inside of the cylinder head water galleries and other places. A potentially very expensive situation.
- - Of course, you can take the heat exchanger to a shop and pay somebody to test it for a lot of money - or - you can do it yourself with a garden hose and a second piece of garden hose that you fit with a spray nozzle or shut off valve.
- - Using pipe clamps attach the garden hose (house supply) to one of the raw water inlets on the heat exchanger. Attach the short piece of garden hose with the spray nozzle to the other raw water outlet fitting on the heat exchanger.
- - Turn on the household spigot to the garden hose (nominally 30 to 60 psi) and slowly close the spray nozzle. This will pressurize the heat exchanger raw water side. If there are any leaks inside the heat exchanger, water will run out of the inlet/outlets of the engine fresh water coolant side of the heat exchanger. If that happens - buy a new heat exchanger.

[MitchM]

well despite putting in a new raw water impeller, and thermostat, and cleaning heat exchanger tubes of 2 broken impeller vane, etc. the engine was still running pretty hot and was losing about an inch from the antifreeze overflow tank on each run. so last weekend i went through the entire freshwater cooling system: 1) made sure the 3 drains on the engine block were closed completely and not leaking antifreeze, 2) made sure no leakage from the thermostat head or heat exchanger heads. then i put a large white towel under the alt side of the engine after shutting it down and LO saw leakage from the weep hole on the underside of the freshwater pump....easy to see when the alternator cover is removed,(and with engine OFF) you can stick your hand under the pump (located underneath the thermostat housing ) and feel the drips.. seems that when the engine overheated last august 09 due to a piece of rubber clogging the raw water inlet, the heat load may have ruined the seal on the freshwater pump even though I shut the engine down immediately on hearing the high temp alarm. so now i have ordered the freshwater cooling pump $280 and all assorted gaskets. hope next week end is nice and cool so i can put the new pump in....looks like a relatively simple job according to the service manual. stay tuned , any words of advice are moswt welcome .... ???

[osirissail]

A worn out fresh water cooling pump (just like the ones on cars) can definitely ruin your day and cause overheating. Why they have only one bearing with a large side load imposed by the alternator belt is beyond me. If your alternator belt constantly need tightening the culprit may be the fresh water coolant pump. Remove the belt and grab the fresh water pump pulley - if it can be rocked back and forth the bearings are shot. Sometimes you will also see coolant leaking down the front of the engine from the pump assembly.
- - Any missing coolant has to go somewhere. If the leak is external there should be a "trail" somewhere on the engine - assuming you keep your engine clean.
- - If there is no trail then possibly the "worst" has happened and the overheating "blew" the head gasket and coolant is entering the cylinders and being "burnt/vaporized". Also it may leak into the engine oil system and turn your crankcase oil white.
- - A worn out fresh water coolant pump is the preferred problem compared to the other two. Good Luck.