Onan 7500 quiet diesel

[iamalienru]

I recently drained the radiator fluid in my onan 7500 as general maintenance. When I repaced the fluid it seemed to take only about a quart of fluid I am pretty sure it is suppose to take about 4.5 quarts. Anyway now when it get up to temp is shuts off. My question is...is there a fluid bleeder on the block of diesel engine? I feel like I could have some sort of air trapped that won't allow the extra fluid. I have read all the posts on the temp sensor and belts to the pump. I just can't figure out why all of a sudden it won't take anymore fluid and if for some reason it is full why it is shuting down

[FIRE_UP]

iamalienru

Glad I could be of assistance. I hope it continues to run well. The physical components of the 7.5QD are really not very complicated. A few thousand 10 MM screws (just kidding) and, all the panels are off. Then, you simply look at what needs to come off next, to achieve access to what ever you're trying to work on. Glad it went well and there was no corrosion on the sensor. I don't know if you saw the pics of mine or not but, mine was severely corroded and I had one heck of a time removing it. And, my coolant as crystal clear, green I should say.
Scott

[RedG]

FIRE UP wrote:
iamalienru
What you need to know is, there is a certain "flow" direction of cooling air inside that generator housing. Yes, air is drawn up, into the bottom front. It starts it's cooling process by cooling the rotor and stator. From there, it travels through the radiator. From there, it's forced through the radiator due to the fact that the center "bulk head" is sealed against the top panel of the generator. That air has no choice but, to go through the radiator.

From there, it's channeled around both mufflers, and, finally, it is jettisoned out the bottom towards the rear. So, yes, to get proper cooling, the top panel "MUST" be in place for the channeling of the air to be effective. Hope this helps. By the way, was there any corrosion around the actual sensor tip?
Scott

X2
I ran mine with the top off one time and it heated up and shut down.
Lesson learned.

[iamalienru]

Thanks Scott for the confirmation of my thinking. This is an important bit of information. My thinking was that if the unit was completely open it would run cooler. Channeling the air with the unit inclosed forces the air through the radiator and other componets thus creating the cooling. I probably didn't need to replace the other parts but it is still good to know they are new. There was no corrosion on the temp sensor but the fluid did look a bit rusty. thanks again Tom

[FIRE_UP]

iamalienru
What you need to know is, there is a certain "flow" direction of cooling air inside that generator housing. Yes, air is drawn up, into the bottom front. It starts it's cooling process by cooling the rotor and stator. From there, it travels through the radiator. From there, it's forced through the radiator due to the fact that the center "bulk head" is sealed against the top panel of the generator. That air has no choice but, to go through the radiator.

From there, it's channeled around both mufflers, and, finally, it is jettisoned out the bottom towards the rear. So, yes, to get proper cooling, the top panel "MUST" be in place for the channeling of the air to be effective. Hope this helps. By the way, was there any corrosion around the actual sensor tip?
Scott

[John___Angela]

Right on. How did the sensor change go. No breaky??

[iamalienru]

update I changed out the temp sensor and the thermostat, changed oil filter and oil....new fuel filter and new raiator fluid closed it all up and and it runs perfectly. I noticed that when i closed the top on the generator that there was considerable air draw from the bottom of the housing. Does closing it up aid to the air circulation? I may not have needed to do all of this to get it running right but now i know where I am at with it. it feels good, sure other things can go wrong but I am more comfortable with it now

[Big_Katuna]

One thing about the video was he said "good for another two years".
I used extended life coolant and was going to go to a four year cycle.
What's everyone's thoughts?

[John___Angela]

iamalienru wrote:
yes they are fun..the unit will run a good 5-10 mins before it will shut down i haven't timed it. the face plate to the radiator fill has list of codes printed on it. It says a single short flash equates to overheat issues and thats what I get. This weekend I will be getting back into it. Soon it will be retirement time and I will have all kinds of time to deal with these issues. I keep learning from these posts they have saved me some headaches. As always I thank everyone for their help

Alrighty. When you get back into it let me know. I have a couple other checks you can do to rule out the sensor but you need a cool morning to check it. Let me know when you want to get into it. We are crossing the line into your beautiful country tomorrow so will be out of Internet contact for a day or two till we get our AT & T chips in the I phones.

Good luck in the meantime.

[iamalienru]

yes they are fun..the unit will run a good 5-10 mins before it will shut down i haven't timed it. the face plate to the radiator fill has list of codes printed on it. It says a single short flash equates to overheat issues and thats what I get. This weekend I will be getting back into it. Soon it will be retirement time and I will have all kinds of time to deal with these issues. I keep learning from these posts they have saved me some headaches. As always I thank everyone for their help

[John___Angela]

Good morning. The overheat should be a fault code of 33 on the detailed fault code, meaning you pressed the button to the off position once after it shut down. What is the timing of the fault. Eg, start a stop watch from the second the unit starts. If it quits after exactly one minute and it gives you the code 33 then it can be either a real overheat or a false overheat caused by the sensor. If it runs till exactly 5 minutes it can be other things which we can discuss at another time if you like.

Good luck with your fault finding. Aren't these things fun???

[iamalienru]

Well now gentelmen yes I sure did see the fault codes flased 3 times at first then a continued flash of one. The flash of one on the panel reads overheat. I think I read where someone said after begining flashes if you pushed the stop button agian it would give a more detailed code. this did not work for me. I really don't think I have a major issue and through a process of elimination i will reslove the problem. I want to change the thermostat as I do not know the last time it was changed. I have replaced the fuel filter, oil and air filter
even though some may not have needed replacement. I now know where I stand with service maintenance with this newly aquired coach. Basically this post was to find a block bleeder outlet to remove air from the coolent system. I don't think there is one and it may not be nessasary to do so. I thank everyone for their comments. Oh the reason I felt it could "really" be the sensor failure is that I have read that this has been a common problem with these generators. This condition will be eliminated through the process.

[JimM68]

Agree with scott. If a QD quits, it will flash a code.
Since our modern world has saddled us with these computers, may as well use the info they give us.

Also, just saying... (as someone who has fixed things for a living his entire life...) If you changed the coolant on a perfectly good working genny, and aren't sure you got enough coolant into it, and now believe it's overheating...

I "really' doubt the problem is the sudden unrelated failure of a sensor...

[FIRE_UP]

iamalienru wrote:
I saw the u tube viedo. i did everthing they said the only thing i haven't tried is wait days for the to escape. I do work for living so getting back to will occur within a day or two. checking for viedo's and online is the first thing i do. At first i did fill through the overflow tank but corrected that and filled through the fill cap under the panel. Now i am still having the same problem. time may be the answer to this. If the engine had a bleed port on the block I figured this would allow the air to escape quickly..I will update this weekend as to my progress. could only be temp sensor or thermostat sticking

Well Sir,

It will help if you say if you've got any codes displayed on your start switch. No need for guessing if one is displayed.
scott

[iamalienru]

I saw the u tube viedo. i did everthing they said the only thing i haven't tried is wait days for the to escape. I do work for living so getting back to will occur within a day or two. checking for viedo's and online is the first thing i do. At first i did fill through the overflow tank but corrected that and filled through the fill cap under the panel. Now i am still having the same problem. time may be the answer to this. If the engine had a bleed port on the block I figured this would allow the air to escape quickly..I will update this weekend as to my progress. could only be temp sensor or thermostat sticking