How do you test your thermostat?

[Hermyboy3000]

I am outside right now and my engine is finally running. But now my engine burys the needle on the temp gauge what gives? Water is going in and blowing out the lower unit as it should. Is my temp sender bad? How do I CHECK THAT? Please help I'm running out of sunlight.

THANKS SO MUCH!

 

[Scaaty]

Re: How do you test your thermostat?

Take the stat out and stick it a pot of water over the stove...see if it opens..

 

[njlarry]

Re: How do you test your thermostat?

Put a thermostat in the water, it should start to open about 10 degrees below the rated temp and fully open about 10 degrees above. Also watch that it recloses about 20 degrees below. The actual reading are in your manual but this will put you in the ball park. Some folks suspend it with a string thru the seat and watch for it to drop.

 

[ziggy]

Re: How do you test your thermostat?

i agree. boil the t-stat. i suspend them in a pan of water, then bring up the temp. i use a thermometer to see the temp of the water.

they start to open at the numer stamped on the t-stat. and are full open at aprox. +20*...........my 140* t-stat would have an operating temp of 140*-160*

as for testing the gage. i'm no pro at this. but think that when ya disconnet the wire at the sender. it should go open. gage would be 0. if ya applied 12v to it. it would read pegged. i suppose it could be the other way around too. but think that when no power and 12v is applied. the gage should do oppisite reading. pegged or not at all......someone can feel free to correct me if i'm out a line.....

 

[Hermyboy3000]

Re: How do you test your thermostat?

I think the thermostat is shot. It's wide open. I stuck it in some really hot water, just shy of boiling and I got nothing. No movement whatsoever.

So should my engine still overheat even thought the stat is wide open?

 

[ziggy]

Re: How do you test your thermostat?

So should my engine still overheat even thought the stat is wide open?

no.....

replace the t-stat for sure.

since ya think ya got good flow out of the outdrive. i suppose the gage could be suspect.

guess i miss read before. testin the temp sender i'd think would amount to puting it in some water. then useing an ohm meter. the warmer it gets the more resistance it would have. or again. could start out at infinite and go twards 0 ohms as it gets warm. i'd think there'd be a spec. for that as to what the resistance readings would be....i don't know them of course......but the resistance would vary in cold vs warm(hot) water....

are ya sure it's not overheating?

does the gage start out at 0 and then as the engine warms up, the needle just pegs? or ya turn it on and it pegs.....

ya've kept us in suspense for long enough hb3000. ......what year & kinda engine and drive ya got?

 

[ziggy]

Re: How do you test your thermostat?

testing gage on my 75 merc. 165hp. w/ ign. sw. off. remove send wire from back of gage. turn sw. to run. temp gage should read 0. turn off ign. sw. jumper wire from send terminal to ground teminal. turn ign sw. to run. gage should read pegged. turn off ign sw. replace sw. if gage did anything other than nothing or pegged.... that's for test of the gage for my rig. yers may vary of corse....


i can't find anything specific for testing a sending unit. i guess ya could look at it this way. if the t-stat is new. and the gage tests good. and it still don't work right, then it must be the sender..........

 

[njlarry]

Re: How do you test your thermostat?

Did the thermostat stay opened or closed? I assume it stayed closed and that's why it's overheating.
Two thoughts; replace it anyway, it's likely due and not worth the time to mess with it and 2) get a 40 buck hand held infrared temp tester, it will tell you for sure the temp of every external part of your engine-risers, manifolds etc. Aim it at the termostat housing and you'll even know what temp thermostat (140/160) you have and if it's working. Can monitor your trailer wheel bearings too.

 

[Hermyboy3000]

Re: How do you test your thermostat?

I've got a Volvo AQ130c 1970. I just got a new thermostat, I'm going to install it tonight but won't be able to test it until tomorrow. The sun's down and most of my neighbors are asleep. I think they'd hate to hear me rev this monster tonight. I will run a test on the gauge and sender tomorrow also.

Thanks folks.

I'll update you tomorrow.

 

[Robj]

Re: How do you test your thermostat?

Don't check a t-stat. If it is suspect, just replace it. It is an important part that you do not want to mess around with, plus they're cheap. Periodic replacement should be a part of regular maintenance. As far as your temp gauge, remove it from the engine, put it in a pot of boiling water and then turn the ignition on. The gauge should read about 210 degrees F, or 100 C.

Have a great day,

Rob.

 

[Scaaty]

Re: How do you test your thermostat?

Don't check a t-stat. If it is suspect, just replace it..

Actually I gave ya way to test it, but RobJ is right...give it the "float test"

 

[Hermyboy3000]

Re: How do you test your thermostat?

Well fellas the stat I picked up at napa doesn't fit. So I am on the hunt for this beauty around town. Wish me luck.

 

[Hermyboy3000]

Re: How do you test your thermostat?

ALRIGHT!! HIGH 5's all the way around. I installed a new OEM thermostat and I no longer over heat. The water coming out of my exhaust is about as warm as bath water. I took her out tonight on the lake and she did wonderful!

I'm not sure if you guys have been following my other threads but I was having a bunch of issues. Most have been resolved!

Even though my stat was stuck in the open position my engine was still over heating. Go figure.

Any how, new stat, no problems!