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mrprostar
02-22-2011, 12:44 PM
I have 96 205 with the 5.7 TBI. My temperature reading was getting very high so began doing some looking around. I replaced the thermostat in the intake manifold (160 degree), no change. I tried to find a replacement for the one in the triangle block but couldn't find one the correct size. So I left it out completely and the temperature stayed lower but when running at any rpm above idle the temperature shoots way up with 190 then plummets very quickly to 120 then gradually goes back to 190 and repeats. I replaced the thermostat in the intake manifold again thinking it was sticking and then finally opening at 190, but it didn't change. I began looking around again and found a wire on top of the thermostat housing that was broken at the connector. I havent been able to find the same connector for a replacement, but was wondering what this wire does and could it have something to do with my problem? I understand that the thermostat I removed it supposed to keep the water in the system warmer so 50 degree water doesnt enter the block, explaining why it the temp drops so fast and so low. But why isn't it opening at 160? Before it would fluctuate from 140 to 165 and never any hotter.

So to stop rambling and get to the point:
What does the wire do?
What is the part number (skidim) for the thermostat in the triangle block?
Where can I find another connector that has the screw into the thermostat housing and then a screw on wire connector on the other side?

Thanks in advance.

JLeuck64
02-22-2011, 12:54 PM
You should check the trans cooler for blockage/obstructions. If plugged from debris that gets sucked out of the water will reduce the volume of coolant flow through your engine.

Oh, and pics of your wire could help the second question...

Barefooter92
02-22-2011, 01:24 PM
Same problem this past summer same boat. Check your trans cooler. This will eliminate 50% of your problem and posts from TT members. This should only take you 2 min to check and clean. Part of my rutine maintenance now.

JimN
02-22-2011, 01:35 PM
I have 96 205 with the 5.7 TBI. My temperature reading was getting very high so began doing some looking around. I replaced the thermostat in the intake manifold (160 degree), no change. I tried to find a replacement for the one in the triangle block but couldn't find one the correct size. So I left it out completely and the temperature stayed lower but when running at any rpm above idle the temperature shoots way up with 190 then plummets very quickly to 120 then gradually goes back to 190 and repeats. I replaced the thermostat in the intake manifold again thinking it was sticking and then finally opening at 190, but it didn't change. I began looking around again and found a wire on top of the thermostat housing that was broken at the connector. I havent been able to find the same connector for a replacement, but was wondering what this wire does and could it have something to do with my problem? I understand that the thermostat I removed it supposed to keep the water in the system warmer so 50 degree water doesnt enter the block, explaining why it the temp drops so fast and so low. But why isn't it opening at 160? Before it would fluctuate from 140 to 165 and never any hotter.

So to stop rambling and get to the point:
What does the wire do?
What is the part number (skidim) for the thermostat in the triangle block?
Where can I find another connector that has the screw into the thermostat housing and then a screw on wire connector on the other side?

Thanks in advance.

Wire color and photos- post both.

These have two temperature senders- one for the gauge and one that reports to the ECM (one yellow one and black wire). If the one with the broken wire has only one wire, that's the one for the gauge and it should go to full cold if you disconnect it. If you short it to ground, it should go to full hot.

Andrť
02-22-2011, 07:27 PM
Doesn't the 5.7 TBI have only one thermostat?:confused:

Double D
02-22-2011, 07:52 PM
This wire?? I think its to the red light on the dash. To hot = red light.

I could be wrong...

ahhudgins
02-22-2011, 08:36 PM
This wire?? I think its to the red light on the dash. To hot = red light.

I could be wrong...

Same set up as my 95 TBI. Mine is put away for another month, but the two sensors on top of the manifold are for the temperature gauge and the over temperature light you mentioned. One has a brown wire, the other has a brown wire with blue trace (I think). My sensor for the ECM (as JimN mentioned) is on the side of the block below the spark plugs. It has two wires: Black and yellow. My 95 only has one T-stat.

ahhudgins
02-22-2011, 09:20 PM
Someone can correct me if Iím wrong, but I still had this old picture from when I was trying to explain to a friend how the thermostat works. I donít know if my 95 has another t-stat below this one, donít know why it would need one?

Lake water leaves the impeller and enters the triangle housing through the large hose in the bottom left (marked with pink arrow) and goes through the housing to the other large hose for the engine water pump which pushes water into the block. Water is also directed up through the small hole to supply water to the exhaust manifolds. Water is HELD in the block until it heats up enough to open the t-stat. T-stat opens up and directs water up (noted by blue line) to the top of the housing and out the exhaust manifolds. An infrared temperature sensor can be purchased for less than $100 to check your actual engine temperature to see if itís over heating or you have a gauge/wire problem.

My 95 uses a 142 degree t-stat that I got at NAPA. Any local auto parts store will have them.

mrprostar
02-23-2011, 11:26 AM
Double D- yes that is the wire. Thank you, I'm sure thats what it is for. I will have to double check, but I don't believe there is a sender on mine like that. I cant find a picture of the connector and the boat is at my parents house. I'll try to get a picture this weekend. But the connector is a little screw without a head on it and it screws into the housing on one end and then the connector is screwed on it with the wired crimped on the other side.

ahhudgins - Also a good picture of the wire on the right side of the picture. Definitely the tan wire. Your explanation is the same as my understanding. The second thermostat I was referring too was in the hole where the blue arrow is and the other one is in the intake manifold, like in the picture.

So what does it do? It looks like it keeps water from entering the exhaust manifolds until its hot?

JimN
02-23-2011, 11:32 AM
Double D- yes that is the wire. Thank you, I'm sure thats what it is for.

ahhudgins - Also a good picture of the wire on the right side of the picture. Your explanation is the same as my understanding. The second thermostat I was referring too was in the hole where the blue arrow is and the other one is in the intake manifold, like in the picture.

So what does it do? It looks like it keeps water from entering the exhaust manifolds until its hot?

It works as a T adapter- to allow cater to go to the engine and it also provides a constant supply of water to the exhaust manifolds.

Jorski
02-23-2011, 11:50 AM
I'm with Andre...my understanding is that only the LT-1 has two t-stats.

I believe that the 5.7 TBI uses one t-stat...160 degree:confused:

mrprostar
02-23-2011, 12:03 PM
I'm with Andre...my understanding is that only the LT-1 has two t-stats.

I believe that the 5.7 TBI uses one t-stat...160 degree:confused:

It was in there from when I got the boat. It is removed now. I will triple check the transmission cooler to make sure it is clear of obstruction. I have cleaned it out several times thinking this was the problem, but I will check it again.

JLeuck64
02-23-2011, 01:09 PM
Sounds like you have done some preliminary diagnosis. Checking the trans cooler is a basic and you have so maybe we can move on...

Check the rest of the raw water intake hoses for blockage/restrictions.

Ever have the raw water impeller burn up? Those missing parts can block water flow through the engine.

How are the exhaust riser gaskets? If they are leaking/seeping down the outside of the ex. manifolds you should probably change them out (can leak internally without being obvious also).

Compression checks? While your checking compression, read the plugs. You're looking for signs that water is entering the combustion chamber indicating a BHG (blown head gasket).

Barefooter92
02-23-2011, 01:33 PM
The LT1 has two sensors as it has aluminum heads and needs more warning before melt down. One on the front and one on the back. The 5.7 TBI has one t-stat at 142F the 160F is installed only if you are using a hot water shower. Either is okay and can be purchased at your local auto parts store. However the local parts store does not carry the 142F.

mrprostar
02-23-2011, 02:02 PM
I have checked for other blockages in the cooling system but will check again. The problem seemed to start when I installed a new impeller. I had some problems with it priming the cooling system when it was on the trailer. I used the bucket method but couldn't get it to suck any water up at first. I shut it off immediately because no water was getting sucked up and nothing was coming out of the exhaust so it didn't overheat. I pulled the impeller and put it back in. I bumped the starter to make sure everything was spinning. I took each line off individually and made sure they were clean. I finally got it to work by holding the water intake hose higher than the motor and filling it with water with it not running. Then it sucked from the bucket just fine. I shut it off and tried it again with the same success. When I got it in the water the first time after that i left it on the trailer to make sure it was taking in lake water and the temperature leveled off. Once it leveled at about 160 I took it out and it immediately went up to 190 and then dropped to 120 and started that cycle. I again took off the impeller and inspected the veins and made sure it was turning. I even tried putting in the old one to make sure it wasn't just the impeller but had the same problem. This is where I'm at. Its workable but its definitely not right.

ahhudgins
02-23-2011, 02:19 PM
If I were in your shoes I would get an infrared temperature sensor and check your actual motor temperature directly at the sensor. I wouldn't want to spend a lot of time swapping thermostats or impellers until I found out if my engine temperature was actually going to 190 degress, or if it was staying at 160 and my guage was changing.

You've got me curious now. I may crawl under my cover this weekend and pull the neck off of my thermostat housing to see if I have another thermostat in the manifold. I thought I only had one where the blue arrow is on the picture.:confused:

mrprostar
03-01-2011, 09:06 AM
So is the one thermostat supposed to be in the intake manifold or the triangle block?

Andrť
03-01-2011, 06:21 PM
Triangle block.
At least,om my 94 TBI...

ahhudgins
03-01-2011, 11:49 PM
So is the one thermostat supposed to be in the intake manifold or the triangle block?

Is your "triangle block" identical to the picture I posted earlier that shows the temperature sending unit with the tan wire? If it is, I see no need to have a T-stat to be in the intake manifold. The T-stat in the top of the triangle block is all you need. As others have mentioned, lake water is supplied the the exhaust manifolds all of the time thru the small hole, once the T-stat opens up it just mixes the warm engine water with the lake water out to the exhaust manifolds. It sounds like some one removed the whole neck from the intake and saw no T-stat and installed one. Maybe?