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Overheat light but ok temp and oil pressure

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    Posted: May-30-2020 at 8:14pm
My season is off to a bad start already, this is my blog post on it if you want a good man vs squirrel story.
Now Today!!! Just got a the big red "engine overheat or oil pressure loss" light on the dash. But... The temp gauge is reading 140 and the oil pressure is good.
I turned off the boat and let it totally cool down for a few hours. Started and it was fine, as soon as the temp gauge hit 140 the red light came on again again.
Ideas?

It just ruined a Saturday. Worst part is I had the kids spend 1.5 hrs cleaning the boat as a requirement before tubing. Then no tubing. Angry kids, wife, and boat owner.blog post

As a side note. There appear to be two temp sensors near the water pump? Is one for the light and one for the gauge?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: May-30-2020 at 9:47pm
Originally posted by BaccoBouncer BaccoBouncer wrote:

My season is off to a bad start already, this is my blog post on it if you want a good man vs squirrel story.
Now Today!!! Just got a the big red "engine overheat or oil pressure loss" light on the dash. But... The temp gauge is reading 140 and the oil pressure is good.
I turned off the boat and let it totally cool down for a few hours. Started and it was fine, as soon as the temp gauge hit 140 the red light came on again again.
Ideas?

It just ruined a Saturday. Worst part is I had the kids spend 1.5 hrs cleaning the boat as a requirement before tubing. Then no tubing. Angry kids, wife, and boat owner.blog post

As a side note. There appear to be two temp sensors near the water pump? Is one for the light and one for the gauge?


As a guess I'd say #1 is for the gauge and #2 is for the warning light but I'd probably get it wrong.

If you were ground the terminal on #1 with the engine running you should have your temperature gauge peg in the high direction if it's the sensor for the gauge. If it doesn't then ground the connection at #2 and that should peg it high. (edited since yesterday)

Or you could go by the wiring diagram and it says the temp sensor for the gauge has a tan wire hooked to it, and the switch for the warning light has a green wire hooked to it, assuming the wiring hasn't been screwed with in the last 23 years .

If you know the temperature is good (your hand would definitely know whether the temp was 140 or 200 degrees or use an IR gun) you could disconnect the lead from the temperature switch that gives the Red warning light and drive it to keep the wife and kids happy and order a new temperature switch to replace it and get the temperature warning feature back to being functional

Nothing else is fed by that temperature switch.

And while you're at it, hook some tubing to your fuel pump rupture diaphragm overflow line going up to the flame arrestor.

I guess the carb conversion worked out for you
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BaccoBouncer Quote  Post ReplyReply Direct Link To This Post Posted: May-30-2020 at 11:33pm
Keno,
Thanks I'll check that out tomorrow in the light and figure out which is which. So there is no oil sensor feeding that light as well. Only the temp sensor?
The Carb conversion worked out well. This will be it's second season. I was wondering what that connection was on the fuel pump. So if the diagram rips it will pump the fuel out of that port, plumbed to the carb it will flood the motor and kill it? That's the idea?
Thanks Again!
Adam
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: May-31-2020 at 7:23am
There is an oil switch that feeds the light.too.

It should be in a tee that also feeds the oil pressure sender.

And your description of the connection on the pump is right.

I edited the previous post from last night to make it maybe easier to figure out which is which

It could be that your oil pressure switch is turning the light on, but your description of it happening at the same temperature both times kinda points to the temperature switch as the culprit. If it was a bad oil pressure switch it would most likely turn on the light as soon as the engine was running.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BaccoBouncer Quote  Post ReplyReply Direct Link To This Post Posted: May-31-2020 at 11:35am
What is the correct running temp? I'm running without a thermostat and run at 140.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: May-31-2020 at 11:42am
Originally posted by BaccoBouncer BaccoBouncer wrote:

What is the correct running temp? I'm running without a thermostat and run at 140.

Adam,
Is the 140 per the gauge or confirmed with an IR temperature gun?

Why no T stat? Have you been having problems?





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Post Options Post Options   Thanks (0) Thanks(0)   Quote BaccoBouncer Quote  Post ReplyReply Direct Link To This Post Posted: May-31-2020 at 1:24pm
It's not the temp sensor. That works as intended. I took it off and the light didn't go out, I ground it and it goes on.
It's the pressure sensor.
I have a few questions and one is TERRIFYING!!!!!
The top threaded part of the sensor moves like a plunger. I assume it is supposed to. I was excited that the oil leak was from the sensor and it was just ordering a new sensor and that's that. But here is the terrifying part. i took the sensor out of the block and the threads look fine. I put it back in (and didn't use teflon tape or sealant because it needs to ground (I am assuming).

When I started it back up oil pooled around the base of it. But I see no reason for it to be from the threads after putting them in, it went in correctly and felt like an NPT thread should, visual inspection showed no issue. If it's not coming from the sensor base is it coming from around the head gasket?????? Did the overheat when the acorn blocked the water inlet blow the head gasket?

The only other thing there is the intake manifold and I don't recall (nor would it make sense) that there are oil passages under there? Unless it also covered a section open to some area on the top of the block that has a seal like the distributor that is leaking. But even if it did there would be no pressure to force the oil out.

No blue smoke burning and don't see oil in the water from the exhaust.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BaccoBouncer Quote  Post ReplyReply Direct Link To This Post Posted: May-31-2020 at 1:28pm
I haven't confirmed the temp. I have a temp probe, where would I check it? What temp would I see with an IR gun since I would be measuring the external metal which has convection cooling and is a big heat sink?
I couldn't find the correct thermostat last year and ran without one when I had a response in a post that someone else runs without one. I grabbed a '97 truck GM 5.7 L one but I think it switches at 190F. I wanted to check that this is ok before putting it in.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jonny Quest Quote  Post ReplyReply Direct Link To This Post Posted: May-31-2020 at 2:34pm
Bacco:

You really need an Infra-Red Temperature gun. Very handy. You can "shoot" the various pieces of the cooling system and get a good idea about the status of each. I try to shoot the whole system (with the engine running) when I'm diagnosing:

- Raw water pump to ensure that it's cold and approx lake temperature
- Thermostat housing to get a feel for the temp where the thermostat is opening
- Intake manifold at the water passages to verify temps there
= Engine block in the area where the cooling jackets are to verify temps
- Exhaust risers

In my last boat (1994 SNOB) one spring, the temp gauge hit 200 and didn't drop below 180. I had a 160 degree thermostat with a new raw water impeller, so I was a bit puzzled. I went back to the truck and got my I-R temp gun. I shot all the cooling system components and everything looked OK. It turned out that I had a bad temp sending unit. Now, there is an I-R temp gun in the glove box of the new SNOB.

To answer your "heat sink" question....when the engine is at operating temperature and things are working properly, the heat produced by the internal combustion is dissipated by the cooling system in a balanced sort of way. If some component of the cooling system is NOT working, then that balance is thrown off. If you shut the engine off and let it sit a while (with no water flowing through the engine) the water that is remaining in the engine will rise in temperature above the thermostat set level. If you have a shower on the boat, you know what I'm talking about. When the engine is operating at idle, the shower temperature is perfect. Shut the boat off and let it sit for several minutes and then turn the shower on without waiting to purge the engine water first. Careful that you don't get scalded!

One option is to cap-off and/or remove the oil switch and temp switch. Just pay attention to the oil and temp gauges. The big red light is designed to get your attention so that you don't totally fry the engine. Again, in my old 1994 SNOB the big red light was disabled. When I removed the ProTec system, the oil pressure "switch" and temperature "switch" were useless as the ProTec ECM was removed. At first I left both switches in, but I later removed the switches and capped / plugged the holes.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote BaccoBouncer Quote  Post ReplyReply Direct Link To This Post Posted: May-31-2020 at 2:40pm
ok thanks, I'll grab an IR gun.

right now most freaked out about oil leak. I don't want to run if the head gasket is blown.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BaccoBouncer Quote  Post ReplyReply Direct Link To This Post Posted: May-31-2020 at 7:33pm
It looks like the oil is coming from the top of the sensor. I am crossing my fingers that is it. Thanks for the help everyone.
-Adam
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gary S Quote  Post ReplyReply Direct Link To This Post Posted: May-31-2020 at 8:12pm
If your really worried and want to check it out some more clean it all off with brake cleaner then run it for a bit then dust the areas you suspect with baby powder- it will only stick to the oil. But don't over think it,it's most likely the sensor
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: June-01-2020 at 12:03am
A failing sensor could certainly provide an oil leak.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BaccoBouncer Quote  Post ReplyReply Direct Link To This Post Posted: June-01-2020 at 12:41pm
I looked at it last night after taking the kids tubing (so oil was thin and hot) and it was definitely coming out of the top of the sensor Yeah!!!!!!! Very relieved. What other parts suppliers do people use in addition to DIM for this sort of thing? Did anyone have a spec on what temperature the thermostat should switch at? I imagine the 190 one I have is a bit high even though that is the center of the gauge on the dash.
Thanks, Adam
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BaccoBouncer Quote  Post ReplyReply Direct Link To This Post Posted: June-06-2020 at 10:58pm
Ughhhhhhh!!!! I put a new pressure sensor in and I still got oil from it. So I took out the sensor and put a plug in it to see more closely what is going on. I cleaned around the plug so it was dry. I watched it and had my wife rev to 3K RPM. The oil is coming from under the intake manifold??? I marked it with a red line in teh picture. Is there even an oil channel in there? I did replace this intake manifold when I put the carb on, but I don't recall an oil channel running through it.
The red arrow points out the seal location between the manifold and block.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jonny Quest Quote  Post ReplyReply Direct Link To This Post Posted: June-07-2020 at 2:37am
Chevy small blocks are notorious for oil leaks at the rear of the intake manifold by the distributor -- also known as the ‘China Wall’.
Tips for preventing oil leaks at the China Wall when installing the intake manifold:
- Use a high-quality silicone sealant and lay down a very thick bead at the front and rear block rib. Use no gasket – only the silicone sealant.
- Set the intake manifold in place allowing the silicone to squeeze out.
- Install all the intake manifold bolts, BUT, only finger tight !!!
- Allow the sealant to set-up for 48 hours.
- After 48 hours torque the intake manifold bolts.

What you are doing by letting the sealant set-up for 48 hours before torquing is preventing it from squeezing out too far and either creating a leak or worse having some of the sealant fall into the engine valley. When you torque the cured silicone sealant you’ll have a formed gasket that shouldn’t leak or blow out with excessive crankcase pressure.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote BaccoBouncer Quote  Post ReplyReply Direct Link To This Post Posted: June-07-2020 at 4:29pm
JQ, Thank you that is great
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: June-07-2020 at 9:32pm
It is best to lay the intake in place and examine the gap between the block and manifold at the front and rear china walls.   This way you know in advance how thick to make your silicone bead. I would lay your silicone on thick enough so you know it is thicker than the gap you witnessed.   Maybe 1 and 1/2 times as thick as the gap max. Too thin and you will leak for sure. Too thick and excess silicone globs can be left inside your engine to cause other issues down the road.   
Silicone is a very good sealer for the China walls, I use it every time, just don't get carried away with too much silicone.
As far as letting it sit before torquing, I'm not a believer in that.   I put it together and torque it down right away . Your silicone will seal up just fine.   I learned this from my customers who built hundreds of small block chevy engines every month. Not one lets them sit before torquing.   They don't have leaks or comebacks due to China wall failures.
The rubber gaskets the intake kits come from are much more prone to leak than Silicone.
I do know some guys that use "The Right Stuff" for this job but not the production engine builders because Silicone is fast and it works.   The Right Stuff is very good product but costs about 5 times the cost of silicone and when you need to remove that manifold some day you will need a crow bar to break it loose. The Right Stuff will not release easy.
It is great stuff but you better be sure you want that extra strong seal before using it.
I definitely would let the silicone set up after torquing for at least 8 hours before you start your engine you don't want crankcase pressure to blow out your wet silicone on start up.
Hope this helps.

Mark
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BaccoBouncer Quote  Post ReplyReply Direct Link To This Post Posted: June-08-2020 at 3:34pm
Mark,
Thank you. That is very helpful. I pulled the intake off last night and saw that I had used the pre-made provided rubber china wall seals. They just got squeezed out (to the inside) leaving a big gap perfectly open for oil to flow out. So I will use the Permatex ultra black as mentioned.
I watched several videos on small block intake manifold installs. When you see that each pro has their own special recipe you know it is a tricky assembly. THere was all kinds of crazy advice. One guy used the provided pre-made rubber seals, looked at how they squeezed and knew he needed to pull them out and then use just silicone. So basically what I'm doing except he did that full cycle in 30 minutes and mine is over a year and a half. The difference between us is that he knew to look at how the seals seated. Now I have that experience.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jonny Quest Quote  Post ReplyReply Direct Link To This Post Posted: June-15-2020 at 1:20pm
Bacco:

You're on the right track. The Ultra Black is good stuff. That's what I used on my 351W when I put a new Edelbrock intake on. The first time, I didn't quite do it properly so I had s very slight oil leak. I took it off and re-installed with the method I described above. Bingo. No leaks. You are correct about the mechanical "opinions". Ask 10 mechanics and get 15 responses.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote BaccoBouncer Quote  Post ReplyReply Direct Link To This Post Posted: June-15-2020 at 5:30pm
I did the Ultra Black and it is working well, Totally dry. What I had done before, that caused the leak, was the rubber seals that come with the intake manifolds. One squeezed in so it left a perfectly open section, worse than if you had not used a seal at all.
But.....
I noticed that my intake manifold doesn't' use all the last set of cooling channels. Does this matter? Is the engine dependant on this to get even head cooling or is it just for the intake manifold if it wants it?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: June-16-2020 at 10:52am
Originally posted by BaccoBouncer BaccoBouncer wrote:

I did the Ultra Black and it is working well, Totally dry. What I had done before, that caused the leak, was the rubber seals that come with the intake manifolds. One squeezed in so it left a perfectly open section, worse than if you had not used a seal at all.
But.....
I noticed that my intake manifold doesn't' use all the last set of cooling channels. Does this matter? Is the engine dependant on this to get even head cooling or is it just for the intake manifold if it wants it?


That's perfectly normal. No water to the back of the manifold.

The heads have ports front and rear so that the same head can be used on either side of the engine.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BaccoBouncer Quote  Post ReplyReply Direct Link To This Post Posted: June-16-2020 at 12:58pm
ok great! Thanks.
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