5.0 GXI-B Wont get up to temp

[BRICH1260]

Took my Chap out for its inaugrial run this weekend. Everything worked well except for the fact that The engine would not get to normal operating temp (160). It hovered around 120 all day. Prior to this season I had replaced the thermostat and the raw water pump. The temps were verifiyed with an IR gun at several points on the block, so I don`t think its the guage. Any suggestions on what might be amiss?

 

[sutor623]

Re: 5.0 GXI-B Wont get up to temp

Faulty thermo stuck open?

 

[BRICH1260]

Re: 5.0 GXI-B Wont get up to temp

I thought about that, but knowing that the thermostat is brand new, I started to look elsewhere. Funny thing is it did the same thing last year (ran cool), thats why I replaced the thermostat after the season. Now I have had two thermo`s that both ran cool? Doesn`t make sense.

 

[Don S]

Re: 5.0 GXI-B Wont get up to temp

Is the thermostat up inside the thermostat housing and held up there with an o-ring?

 

[BRICH1260]

Re: 5.0 GXI-B Wont get up to temp

Don, it was when I reassembled it last fall. I distinctly remember pressing the o-ring in place. Should I dis-assemble and inspect. Is that the most obvious source of the low temps?

 

[Don S]

Re: 5.0 GXI-B Wont get up to temp

The thermostat is the only thing that can make the engine run cold. Lots of things will make it run hot, but only one will make it run cold.

 

[BRICH1260]

Re: 5.0 GXI-B Wont get up to temp

I`ll take the housing off and see what I can find. Thanks.

 

[Don S]

Re: 5.0 GXI-B Wont get up to temp

Your other post is about trying to find a sending unit, why? If you used the IR temp gun and got the same readings, changing the sender isn't going to make it run any warmer.
Did you use the temp gun next to the sender? That's where you should be to see if the gauge is reading right. You also have a built in temp gauge in the ECT sensor for the ECM. If you hooked up a diagnostic computer to the engine, you could see if the ECT matches the temp gauge at the helm.

 

[BRICH1260]

Re: 5.0 GXI-B Wont get up to temp

Yea Don,I know. I am just basically planning things out at this point, just in case I have to replace something. Just like to think ahead. I am still planning on pulling the thermostat housing, here in the next couple days, and double check the thermostat, to make sure it is not jammed or dis-lodged. It`s got to be in the gauge, thermostat, or sending unit somewhere. I`ve just got to eliminate them one by one. As always, appreciate your insight.

 

[Don S]

Re: 5.0 GXI-B Wont get up to temp

Then before you take it apart, use your IR gun to verify the temp sender reading on the gauge or use a scan tool.
Don't spend a lot of time looking for parts until you need them.

 

[BRICH1260]

Re: 5.0 GXI-B Wont get up to temp

I took off the thermostat housing last night. The thermostat appears to be good working order, not plugged and still in place, so I can rule it out of the equasion. I am beginning to think my guage is not woring properly, any way of testing the guage?

 

[Don S]

Re: 5.0 GXI-B Wont get up to temp

I closed your thread in the boat topics forum, please don't post the same problem in multiple forums.

On to your problem.
I have asked in a couple of replies if you checked the temp with the IR gun at the same point as the sender. Did you??? If so was it the same?
I also told you that you can verify temps with a scan tool.

In your original post you stated you checked multiple spots on the engine, did they show low temp also.
You can't blame the problem on the gauge if the engine is actually cold.

 

[BRICH1260]

Re: 5.0 GXI-B Wont get up to temp

Don, I did check the thermo housing with the IR gun and it was very close to the 120 reading on my guage. I did have a higher reading at the exaust manifolds of about 140. Last night I tried to get a reaction from the guage, to make sure it was good, by jumping the two wires going into the sending unit momentatily, with the ignition on, and nothing on the guage twitched. Just trying to rule out all possibilities within my abilities. Thanks again.

 

[Don S]

Re: 5.0 GXI-B Wont get up to temp

If you was getting very close to the same readings with your gun shooting near the sender, then you don't have a gauge problem. It's reading what the temp is. The risers will be warmer they have hot exhaust running through them.
Your problem is the engine is not warming up past 120?, you can change gauges and senders for days, but they won't make the engine get warmer.

Does the engine run any warmer under load for a while or does it stay at 120?

 

[Don S]

Re: 5.0 GXI-B Wont get up to temp

Been thinking about this problem. One other thing it could be is the thermostat housing itself. If you look at the flow diagram below, you will see there is a bypass hole in the housing so that water will go to the manifolds and risers even if the thermostat is closed. If that hole has corroded away and is larger, or maybe a chip out of it to enlarge the hole. It would let cooling water from the engine pass as well as water from the seawater pump. Especially if the sea water pump is a bit weak in pressure. How old is the impeller?

View attachment 5.0 cooling.pdf

 

[BRICH1260]

Re: 5.0 GXI-B Wont get up to temp

The impeller is brand new. The guage does not fluctuate. The lowest setting on the guage is on the left side, 120 and it never lifts from that lowest setting.

 

[Don S]

Re: 5.0 GXI-B Wont get up to temp

Remove the wire from the sender. With the ignition switch in the run position, tap the wire to a good clean ground and see if the gauge pegs to max.
Don't hold it pegged, have someone else watch the gauge. If you leave it there to long, you will need a gauge.

Still don't understand why your IR gun is reading the same as the temp gauge and you want the gauge to move.

 

[BRICH1260]

Re: 5.0 GXI-B Wont get up to temp

I`m just grasping at straws right now, so fustrated. Seems to be a relatively simple system to understand, yet it`s kicking my butt. I`ll try to rule out the guage with your grounding suggestion and try to rule out the guage. I will be taking her to the lake this weekend for some more diagnostics. I`ll post my findings next week. Thanks.

 

[BRICH1260]

Re: 5.0 GXI-B Wont get up to temp

Ran the boat over the weekend. I did get some slight fluxuations on the Temp gauge, not much, but it did rise a little, say to 125, primarily while at idle. So I think the guage and sending unit are working. Still perplexed as why it still runs cold, anything else to try?

 

[Don S]

Re: 5.0 GXI-B Wont get up to temp

Get another thermostat and try it. Wouldn't be the first new part that didn't work right.