GIORGOS8888

After T-stat change , temperature gauge on dash fails

25 posts in this topic

Hi to everybody and I wish a mild winter.

In this issue the facts are as follow:

1)When I replace the impellor water pump with a new brass pump GLM 12097 in my raw water engine I saw that from my old impellor was missing a small rubber part of 1 cm lenght and half cm wide.I never found this small rubber piece somewhere in the system when I did flush back.

2)I had dismantle only the thermostat housing and the impellor pump .Not any hoses from coolers ,elbows,manifolds etc.

3)The flash back water flow was seem to be a free flow ,not blocked.

4)Also I did not check inside the t-stat housing with a wire if any small rubber pieces stuck there in (I do not know if this is correct to do)

5)I did flush back the cooling system from t-stat dismantle hoses looking at the impellor pump dismantle hoses if will come out the small rubber piece,plus from the central exit of engine where fits the t-stat.

6)After I put in place the new T-stat ,2 new gaskets (big & small) ,new sleeve and had assembled the whole system I start engine and check for leakages .Not anyone.

BUT even after 10 minutes of engine working the temperature gauge on dash (which before the impellor pump change was working correct) was not moving from the minimum indication except when I push the throttle at 1200 engine RPM It was moving a little up and immy again down to the minimum indication.

The surfaces on t-stat and it's base on engine are clean and not any paint or dirty over there ,where the new gasket exists ,so I cannot imagine that may be not good ground for the sender etc.

Any ideas please ?:)

Share this post


Link to post
Share on other sites

Check the continuity from the t-stat housing to the block. Did you use sealant on the gasket surfaces/bolt threads? Did the gasket have brass continuity rings?

s-l1000.jpg

Share this post


Link to post
Share on other sites

Thanks for your answers:)Yes I reconnect the wire that goes to the sending unit that's on the T-Housing.I did not put any sealant on the gasket surfaces/bolt threads. The gasket has brass continuity rings and is the same one as on your attched pic. above.

Share this post


Link to post
Share on other sites

I installed the thermostat wrong on my old boat (forgot 1 o-ring) and it overcooled until I fixed that o-ring!

Share this post


Link to post
Share on other sites

Engine runs at idle & stays cold forever. Why do I think the NEW thermostat is defective. If you still can find the old thermostat ? Put it back in. With new gaskets of course. Wires are connected because the temperature rises at 1200 rpm.

Quick check with your hand. Run the engine to you get a HOT to YOUR HAND ONLY. Did the gauge read what your hand felt ?

Hope your parts guy did not screw up again.

Good luck

Share this post


Link to post
Share on other sites

Surfaces are clean like a new brand.The whole system -engine -boat is like new-.even with 675 hrs on engine .Also I clean the paint from t-stat surface to engine block to bare metal for good contact of the gasket brass continuity rings (as above picture gasket-Not sure if this is correct) may be have rust later there. :scratchchin:

This time cyclops2 I bought all stuff from Mercruizer shop and is original Quicksiver.New T-stat to 160 degrees same as old one.Everything in the plastic bags of quicksilver with OEM code # on them.I have keep the old t-stat which was working perfect.May be I will change again if we do not find another solution here.

Sometimes with rpm steady to 1200 it climbs a little bit more than 120 up to 140 for max. 2 seconds and back again to 120 like the t-stat is always open and close for only a while.This confuses me.It was close as it is new when I put it on:)but shows an opposite behavior. My hand stays comfortable on the manifolds,I do not have a laser temp. instrument to check if temps are same of gauge and exhaust manifolds.But Ii work the engine two times from 10 minutes each and behavior is the same.Even if t-stat is defective I think that it should work even for one time and after reach the temp to stay open if defective?If that makes sense.

Any more ideas ?before I put back the old one t-stat?

Share this post


Link to post
Share on other sites

Did you try to ground the sensor wire and see if the gauge maxes out. That will eliminate the gauge and wiring. Any chance the rubber piece is hung up around the sensor restricting water flow. Maybe remove the sensor and make sure you are getting water flow by it.

Share this post


Link to post
Share on other sites

I will ground the sensor to check it.Also I will check for the rubber piece if in the t-stat housing around the sensor etc.(May be already out from the exhaust ,may be somewhere in the cooling system or exhaust maniflods -I hope no-.I do not know.)But if in case has stuck in the new t-stat that would mean that at least one time engine temp. had reach 160 degrees and then it open.But this not happen not even one time.I was looking the gauge and never went more than 120 except as I mention in above my messages .Anyway I understand that I have to take it apart one more time and check in.But as this will happen probably the weekend,any more ideas are highly welcome:)Thank you all of you.

Share this post


Link to post
Share on other sites

Very easy & SAFE way to test a thermostat. Pot big enough to hold water covering the thermostat by about 1" or more. NEED a thermostat to see the water temperature up to 200 F Or 100C. I buy them at a food store in the USA. There is a TOP UP side to thermostats. Heat the water on high heat to speed it up.

Post back the early opening temperature & fully open temperature. Do it 2 x to get the feel of it opening.

Share this post


Link to post
Share on other sites

OK cyclops2 I will do this also and I will post back the temps.:)First I have to find the thermostat up to 200 F Or 100C.But I will try it.Just to see the result.By the way ,is it correct that I took out the paint from t-stat surface for better contact to the continuity rings?Or better to paint it again when I will take it apart?:)

Share this post


Link to post
Share on other sites

I am sorry use a ..........THERMOMETER..............of 200 F or 100C range. Medications are hitting.

Share this post


Link to post
Share on other sites

In the automotive world if you can turn the belt more than 90 degrees between the two furthest pulleys it is to loose. Also you don't want it tight like a piano string either. For a more exact tension you will need a belt tension gauge and the exact spec from the manufacturer.

Share this post


Link to post
Share on other sites

Cyclops2 I did nt write thermostat for laugh,just I am sleeping on my laptop :)it is past 3 am here .I understood what you mean.I am sorry I repeat it mistake written.But its funny anyway,for both of us:)

Thank you Mi3sons .Regarding the belt pls we can continue in my other post.

Share this post


Link to post
Share on other sites

Do you check to see if you have the T-stat in backwards?

That will make it run cold, and the engine will not get up to temp. Denny.

Share this post


Link to post
Share on other sites

Denny,to be honest I was thinking very seriously abt this backwards, last night.But no , I put it back as I took it apart and is like this diagram http://www.marineeng...0-thru-0m299999

When you open it , then check the standart cooling diagram.

Great! NO mechanical issue, that was the only help that I could offer.

Hope you find your issue soon. Denny

Share this post


Link to post
Share on other sites

Maybe take it apart, clean the surfaces real good and reinstall with a new Gasket... Doesn't really make sense if it worked before.

Thats way I mentioned to check the ground. If the ground is good, than way take it apart. Its too easy to check first.

Share this post


Link to post
Share on other sites

What IDIOT could possibly design those STUPID PAPER THIN BRASS washers to survive in fresh or SALTWATER ???????????

DEFINATELY a costly repair for dealers to make a killing on a fleecing of engine owners.

A person with a wet salt water washer is reassembling a battery.

Share this post


Link to post
Share on other sites

To make the long story sort , I left it as it was and put the boat in the water.I was cruising 525 nautical miles that summer.T-stat was working perfect from the first moment when boat in the sea.Temp gauge on dash steady at 160 degrees.After all these miles, when boat again on trailer on land during engine flashing with fresh water (after summer) happened again the same as described at the beggining of this topic.I was not worrrying any more,I was laughing.It seems as the new t-stat was very sensitive when on trailer.Next summer (last summer) when in the sea again ,everything was working correct ,again!Also no more surprises after the 2nd summer when flashing engine on trailer.I wrote this back in order to close an open case as many people tried to help me in this my issue here in and I owned a final answer to what had happen finally.Thank you everybody of you guys.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now