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1990 Suzuki DT30 Water Flow Problem

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  • 1990 Suzuki DT30 Water Flow Problem

    Fairly major overheat when an impeller vane broke off and one bit plugged the end of the delivery tube (my fault for improper maintenance and having a non-working flow sensor). All but two small bits of old impeller recovered (maybe 1/8"x1/4"x3/4" at most) and those were either accidentally discarded by me at the beginning or made it all the way up the narrow water delivery tube (hopefully to get flushed out). The impeller has been replaced and water delivery tube rodded out in case anything was jammed part way up. Pump seems to be working just fine -good pee hole stream and a good flow out the water flow sensor port or thermostat port if I leave either open.Overheat was hot enough to start to melt some plastic fittings on block. Only serious damage was to the water flow sensor. Inner part of sensor basically fried and fell into water jacket. I've recovered most of the sensor in the form of melted hunks and flakes through the water flow sensor port and thermostat opening at the rear water jacket. Other small bits could easily have been flushed out unseen. New water flow sensor installed and all seems normal -tested fine, alarms at startup until water jacket fills then goes quiet.Discovered that the overheat caused the thermostat to open so far that one end of the center guide pin fell out of it's rubber retaining collar. Pin was easily re-aligned. A phone call to the regional Suzuki service dealer said these t-stats are pretty tough and there's a reasonable chance its okay based on my description of the severity and duration of the overheat. T-stat seems to be functioning. Good spray coming out the exhaust port soon after warmup then cycling on and off (as in totally off -just pee hole streaming) during idling and at troll speed. Don't have access out here in cottage country to a thermometer for properly testing t-stat -I'll do that later. Should start to open at 155-160 degF, right?Remaining problem is the flow sensor giving an intermittent alarm, every half minute or so from a very tiny chirp to a steadier alarm (typically 10 seconds at most). This all starts happening as soon as the engine is warmed up -within a few minutes of startup.All this tells me there is still something stuck in the water jacket and it's moving around either blocking flow or hitting the water flow sensor. There must be some significance to the fact the thermostat needs to be at least partially open, but I don't know what that is. I'm assuming there's a melted chunk of the old flow sensor and that it lives in the rear water jacket. The reason I suspect its moving around is not only the intermittent alarm, but also the fact that the symptoms sometimes get better or worse after my various attempts at flushing the water jacket and even sometimes when I tilt the motor a little and drop it against the transom while idling. The symptoms also got worse when I tried running without the thermostat installed -exhaust spray was mostly good, but sometimes a little less (but never dead stopped).I've flushed it every which way I can think of -up the cooling water delivery tube in the leg plus in and out of the open water flow sensor and t-stat ports in the rear water jacket. I even tried compressed air up the delivery tube and a suction tube into the water jacket ports.It's starting to look like my only option is to remove the cyl head and maybe the exhaust port water jacket for inspection. On a DT30 it looks like the only way to do this is by lifting off the power head -something I'd really like to avoid. Apart from all the labour, it may take weeks to get the parts and I'll lose the summer.Anybody got any other ideas on flushing? Neighbour suggested his heavy duty power washer with the nozzle into the flow sensor and t-stat openings. Sound like a good idea?Any chance of getting the rear water jacket off without cracking the cyl head off the block? Doesn't seem likely to me. Anyone been able to get the cyl head off a DT30 and torqued back on without removing the power head? The lower 2 cyl head bolts are very difficult to access. I can barely get a 1/4" drive socket on a tiny swivel handle onto them -a torque wrench head certainly isn't going to fit down there. There may not even be enough room to back the lower bolts out enough to free them. The exhaust port water jacket looks even worse if not totally impossible to remove in place.Any other tips or ingenious thoughts? Or have I just about covered it all?

  • #2
    Re: 1990 Suzuki DT30 Water Flow Problem

    Geez that's got to be frustrating, could still be a ****y flow switch, but nothing is always that easy. Have you tried power flushing the unit Fill unit with water, thermostat housing off, seal up all but one of the water pick ups then put your air hose in there, and let it rip for a few seconds. Think you will be surprised with the volume of water that will come out. Obviously give it a few goes, and keep filling with water.Really don't think a high pressure water cleaner will do anything as soon as the water changes direction it will be merely a spray.Hope this helps Justin.

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    • #3
      Re: 1990 Suzuki DT30 Water Flow Problem

      Thanks muchly Justin. I'm pretty confident in the new flow sensor. It's the flip flop mercury switch type. The head moves freely, it checked out perfect on an ohmmeter and it properly triggers the alarm system both when manually triggered and at startup with the water jacket drained.As for using the power washer for flushing, we wwere mainly thinking about just blasting a high flow of water into the jacket to mix things up, but your power flush technique giving it an enema sounds far more intelligent. The boat is still dockside which may make this even easier.If I understand you right, I'll block off the two side water intakes, remove the upper (third) intake water screen and blast water directly up in there with the engine running and the t-stat housing open. The tail can remain submerged while doing this. I can trigger the power washer on and off to get some surging and stop/restart the engine to start the processs with a full or empty water jacket. I can do a similar flush with the water flow sensor port open. Hopefully the power washer will double the efficiency of the water pump. I presume that will give the power flush you're talking about. Wish me luck.

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      • #4
        Re: 1990 Suzuki DT30 Water Flow Problem

        I did a head gasket job last year on my 89 DT30 and I had no problems removing & re-installing the head. The torque is not very high and I used a small 3/8 torque wrench, after removing the spark plugs. My problem was in the water pump and I am still trying to remove it cause the lower unit is stuck.Hope you can work it out.
        Extreme

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        • #5
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          Re: 1990 Suzuki DT30 Water Flow Problem

          I am sure after 5 years (that is how old this post is) he sorted out the problem by now ..... sorry I couldn't resist .... check the dates on the post, if it is older than a month it is more than likely the problem has been resolved .....
          __________________________
          ... THE MAXIMUM HORSEPOWER IS NEVER ENOUGH ...

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