water temp gauge not showing temp -- fixed!

[waterone1@aol.com]

Re: water temp gauge not showing temp -- fixed!

Gary, you should have mail. Your email ended up in my spam folder.

 

[garycinn]

Re: water temp gauge not showing temp -- fixed!

Thanks everyone for getting me back on the water. Family and I had an enjoyable afternoon.<br /><br />I moved the engine back to the original position and used the alignment bar just in the gimbal bearing and moved it around until I could get it in the coupler. Then I fine tuned it until it was even resistence thru the entire coupler, light resistence as I could, and even spline grease markings after removing it. It goes in easily with one finger on the end pushing it and pulls out with a thumb and finger.<br /><br />There is less noise now running with the new gimbal bearing. It took me a day and a half to do it. I think I could now do it in a couple of hours -- with alignment. It was a good experience, although frustrating at times.<br /><br />Put in the new temp sensor.<br /><br />Put the outdrive back on (the right way this time), torqued it down, fired it up in the driveway at 1200 rpm for ~12 minutes and no temp on the gauge.<br /><br />No more leaks inside the boat.<br /><br />Out on the water the only time it shows a temp is occasionally after a run and idling it will climb to ~140. It won't stay very long and then drops somewhat quickly down to ~100.<br /><br />If I shut it off and wait for 10 minutes and turn the key to the on position, the gauge shows ~160. Fire up the engine and the gauge goes back down to <100.<br /><br />So I'm back to my original issue. No overheating, and erratic temp gauge. I have replaced tstat and temp sensor. Gauge pegs to max / past full when temp sensor wire is grounded.<br /><br />It turns out my multimeter had low batteries and showed my old temp sensor was flakey when it really wasn't. After new batteries, it behaved close to the new sensor.<br /><br />Any more ideas on the temp gauge issue?<br /><br />Thanks

 

[waterone1@aol.com]

Re: water temp gauge not showing temp -- fixed!

Gary, great to talk to you today. Sorry to hear the temp guage is still not working. Sounds like it is time to run this problem from the back side.<br />Your temp gauge is really an ohm meter that has temperatures on the face instead of ohm readings. If you disconnect the wires to the temp sender and connect your ohm meter to the temp sender, you will see what is going on there. If your ohm meter shows the same "movement" as the temperature gauge, it is an engine water issue. If your ohm meter "shows" what you would expect the temp gauge should read....then it is in the gauge or wiring. A recent example : Fresh water tank gauge in cabin shows erratic readings. Sender is rated at 30 - 330 ohms (30 ohms full...330 empty) with ohm meter connected to sender I "see" about 350 ohms empty, and as I raise the sender by hand, I see the resistance go down to 30 ohms.....sender is working! I put a variable resistor on the wires going to gauge, as I move the variable resistor I see that it takes about 2400 ohms before the gauge shows empty and any resistance below 600 ohms shows full. I rip apart the gauge and find a cracked resistor inside of the gauge.....replaced gauge...all is well.

 

[garycinn]

Re: water temp gauge not showing temp -- fixed!

WW1,<br /><br />Thanks for your help diagnosing the gauge. It makes sense. It was a pleasure and very interesting to speak to another OH boater and boating enthusiast.<br /><br />I think I found my problem last night. I went back to section 6D in the Merc manual that covers engine cooling thinking something basic isn't working right.<br /><br />It then hit me like a ton of bricks. There is an o-ring depicted on top of the tstat that I don't have installed.<br /><br />I mentioned in an earlier post that my symptoms are like I have an open tstat. If my tstat isn't seated tight with the o-ring, it is as if I have a stat in the open position. This matches my symptoms perfectly.<br /><br />I don't remember taking an o-ring off in the fall, but I can't remember what I did last week much less five months ago.<br /><br />Tomorrow I'll buy an o-ring and take her out and report back. Thanks for everyone's help so far.<br /><br />So, this gauge problem has helped me find my water leak and point me to a gimbal bearing that was on its way out.<br /><br />Gary

 

[garycinn]

Re: water temp gauge not showing temp -- fixed!

Found a source for the cork o-ring gasket that goes in above the tstat. Installed it and still no change -- flaky water temp gauge.<br /><br />I'll have to take an ohm meter to the sender while it is on the boat and see what happens. I didn't take the meter with me today.<br /><br />Very close to taking it in to dealer .

 

[Don S]

Re: water temp gauge not showing temp -- fixed!

Originally posted by waterone1:<br /> Your temp gauge is really an ohm meter that has temperatures on the face instead of ohm readings..

I'm sure you meant milliamp meter and not an ohm meter, since voltage and amperage to an ohm meter would kill it.<br /><br />Gary, you can test your sender with an ohm meter, just don't have power connected to it. One lead on the terminal end and other to ground. As the heat changes so does the resistance (Ohms)<br />PS: you didn't by some chance put teflon tape on the sender when you had it out did you???? If you did, it will prevent you from getting a good ground on the sender and it won't work that way.

 

[waterone1@aol.com]

Re: water temp gauge not showing temp -- fixed!

Don you will notice in my previous post that I told him to disconect the sender before putting the ohm meter on it. I would not describe it as a milliamp meter since we are looking for dropped VOLTAGE across a resistor (in this case thermistor) and not CURRENT or AMPERAGE . In this case the difference between his dash gauge and an ohm meter is that the ohm meter has an internal voltage source (the 9V battery) and his dash gauge has an external voltage source...the boat battery. Both gauges are measuring voltage drop across the sender. We're splitting hairs here, and the important thing that we both pointed out is not to use an ohmeter on an energized circuit.

 

[waterone1@aol.com]

Re: water temp gauge not showing temp -- fixed!

Gary, The other sender in the t-stat housing is the temp sender for the EFI ECM, ten minutes with a scan tool will verify if this is a water circulation problem or a bad temp guage/wiring.

 

[rodbolt]

Re: water temp gauge not showing temp -- fixed!

waterone<br /> its actually more like a milliaamp meter. the ign post supplies 12v, from there it goes through the meter movement to the sender. the sender is a variable resiter. the meter movement is usually controlled by the amount of current passing though the coil on the meter and uses magnitism to deflect the needle. more current is more magnistim. less current less magnitism.<br /> but either way asw long as he tests it as outlined it will isolate the problem. them little pots sold at ridio shack are wonderful little test devices .<br /> most temp gages are actually a two coil device. on is the limiting coil and normally has a dropping resitor in series with it to prevent burn out. the other is a balance coil. the needle deflection is the proportinal difference in current flow between the coils. the limiting coil has a constant current and there fore a constant magnetic field. the balance coil has the current varied by the thermistor(temp sender) and can change. needle deflection is a representaion of the difference of the current in the two coils by the varying magnetic field of the balance coil.

 

[garycinn]

Re: water temp gauge not showing temp -- fixed!

Thanks for everyone's help so far. <br /><br />I'm going to get it on a scan tool later in the week. I would hook up an ohm meter to the sensor as WW1 says, but I'll go straight to the source and see what the alarm sender tells the ECM via the scan tool.<br /><br />I appreciate the sound advice.<br /><br />As always, I'll keep posting until it's complete.

 

[garycinn]

Re: water temp gauge not showing temp -- fixed!

Don, <br /><br />I didn't put anything on the sender threads before installing it. The Merc manuals said to put teflon paste on it, but it came with some red coating (loctite?) that I thought would suffice. <br /><br />To check to make sure I had a ground I rigged a wire from a known ground source. I then touched it to the sender wire -- it pegged the temp gauge. I then touched it on the sender body while the wire was installed and engine running and the gauge didn't move. So I think I have a good ground to the sender.

 

[garycinn]

Re: water temp gauge not showing temp -- fixed!

Worked on it some more tonight.<br /><br />Didn't find the problem, but eliminated many sources.<br /><br />Hooked up the Merc scanner and it had a code set for low coolant temp -- duh! Reset the codes. Left the scanner connected and started it up. The scanner showed the coolant temp to be spot on what the IR was reading on the stat housing.<br /><br />Here is what we observed: when the stat is closed, the scanner read ~65F, when the block got up to 160+ the scanner showed the temp go up to 160F. The gauge shows it climb to ~160. After about 20 seconds, the gauge, scanner, and IR temp sensor all start to drop very quickly (5 seconds) down to 70F again. At that point the block is showing about 140F. Then it slowly starts to climb up to 160F and it does it all over again. This is idling about ~1000 or ~1200 rpm on muffs.<br /><br />We hooked an ohm meter up to the sender and observed the same results. We hooked up a temporary gauge -- same results. For grins, we had another new sender -- same results. We measured the difference between the sender ground and the actual ground and it was essentially zero.<br /><br />So, at this point either I have a really screwed up cooling system, a second tstat that behaves similarly to the original -- incorrectly.<br /><br />Any suggestions? Is this how a tstat on a 4.3L should behave?<br /><br />Several tests are showing the gauge, sender, and ground are all fine. It seems like the tstat is either open or closed -- nothing in between that is causing the huge temperature swings on the gauge.<br /><br />Interestingly, my fuel dilution in my oil last year was 7%, so I must have had a lower form of the problem last year causing the engine to run cool and dump more fuel.<br /><br />Anyone experience anything like this?

 

[garycinn]

Re: water temp gauge not showing temp -- fixed!

I'm embarrased, but I think I have found the problem. I say, think, because it has poured rain all day and I can't get out and test it.<br /><br />I had remembered this post from a month ago on another board:<br /><br /> http://www.boatingabc.com/cgi-bin/ultimatebb.cgi?/topic/3/803.html <br /><br />I went back and looked it over and it hit me. Dang, do I feel stupid.<br /><br />I have the sleeve and the thermostat installation order reversed. I was putting the tstat right on the block with the sleeve above it.<br /><br />If I had paid better attention to my manual instead of a glance at the diagram, it would have been obvious.<br /><br />Here is a diagram for my engine cooling system:<br /><br /> http://media.stemtostern.com/LSDATA/LSDATA_FULL/CRUISER/834987.00/17.GIF <br /><br />I guess there are two chambers in the tstat housing, one above the other and I was blocking water from the block from going to the lower one.<br /><br />If we get any reprieve from the rain, I'll swap and confirm, but this has to be it -- there isn't anything else left to check or replace !<br /><br />Gary

 

[garycinn]

Re: water temp gauge not showing temp -- fixed!

Yes, I'm embarrased. All this goosechasing for an improperly installed tstat.<br /><br />Inserting the tstat into the housing instead of against the block solved the problem.<br /><br />I learned lots of lessons on this one. In hindsight I should have gone back to the basics -- especially since it worked last season. <br /><br />I do think that the missing cork gasket has been my problem with fuel dilution in the oil. When I ran it in the driveway this evening, it stayed steady at about 170F to 175F on the gauge. It never ran that warm last year. It was about 10F cooler on the gauge. I think the ECM was dumping more fuel trying to warm it up.

 

[Wotknot]

Re: water temp gauge not showing temp -- fixed!

Not necessarily THAT problem, but.....we've all been there/done that before. We've all had our "senior moments" in our life time.

 

[tommays]

Re: water temp gauge not showing temp -- fixed!

gary<br /><br />glad you found your problem <br /><br />its very helpfull when another DIY lets people no were they went worng so they avoide the same mistake<br /><br />tommays

 

[garycinn]

Re: water temp gauge not showing temp -- fixed!

Originally posted by tommays:<br /> gary<br /><br />glad you found your problem <br /><br />its very helpfull when another DIY lets people no were they went worng so they avoide the same mistake<br /><br />tommays

Thanks. I was embarrased to admit my basic mistake, but I wanted to document it all and my steps along the way. It is my way of paying back the people that helped out on the thread.<br /><br />This way when someone has an overcooling or flakey cooling issue, they can either find this thread or someone here can ask how their thermostat is installed. Sometimes we forget about the basics and take them for granted and they are installed correctly with all the right parts.

 

[KaGee]

Re: water temp gauge not showing temp -- fixed!

Ona positive note here... you found a gimbel bearing about to poop out on you. And we all know that it would have at the most inconvenient moment.