low coolant light after checking thermostats. air?

[vaicase]

i took the thermostats out and checked them. it has 180's i was wondering is there a way to get the air out. its full of antifreeze. but the low coolant light is on. i drove it down the road. its still on. also is changing to 195,s gonna help or hurt me? i think it has smething to do with the fitting on the top of the double thermostat housing? also where is the low coolant senser anyway? thank you much

 

[Chief915]

low coolant sensor is halfway up the coolant tank back in the corner of the engine bay. its a two wire connector on the front of the tank. There should be a air bleed fitting on top of the thermostat housing. open it up until coolant flows out of it then close it back up. after you warm the engine up, you will have to add more coolant to the tank as it purges the air out of the engine and upper radiator hose.

 

[ak diesel driver]

195s should help your mpg a little. there is a bleed screw on top of the tstats and the low level sensor is in the overflow tank. at least it is on my 96

 

[buddy]

The low coolant circuit is insane. Its a water sensor that goes to its own little processor box that controls the light.

195 t-stats may net you a few more MPG.

 

[vaicase]

thank you guys.

 

[chefmike]

I had a time with my low coolant light. I had to scrape a little corrosion off the inside of the tank and I cleaned the outside connection. I think the PO used leak seal and when the air hit the sensor it coated it.

Scraped and cleaned, and it works now. Helps that I fixed the leaking crossover too!

 

[JMJNet]

The coolant crossover is prone to leaking at the quick connect. Check that!!!

You can replace it with a barb connector.

 

[vaicase]

the only way i figured out how to fix it. was to remove the tank and clean it good. it now works good . no light only when its low. like it should. thanks for the reply posts.

 

[amc454]

I just went for a drive today, And I was running it real hard. racing around with dad on back roads some... anyway, low coolant light came on, truck got a little warm, not over heated to the red, but warmer than normal. I shut it off, popped the hood and let it cool for a a little while, checked the coolant level and it was good. Fired it up, temp came back to normal, light went off. Drove it about 3 mile, and it died at random when I let off the throttle. Fired right back up, and did it about a mile later. less than half a mile after that, it died and didnt fire back up till I pulled off to the side of the road. Once it fired again, the low coolant light came back on, I drove it another mile or so back home, and the coolant light remains on... the truck is running a little funny now, when its idling it will seems like it skips or misses a tad, as well as when you rev it up, but not a consistent miss as if it were a timing issue. All I can say is this truck is turning out to be a head ache, and I am really hoping it doesnt throw another big issue in my face. Any help would be really appreciated.

 

[chefmike]

All I can say is this truck is turning out to be a head ache, and I am really hoping it doesnt throw another big issue in my face. Any help would be really appreciated.

Welcome to the TruckStop! Folks are going to want to know ALOT more to help you, but you have come to the right place.

First- add a signature by using quick links-edit signature. Put in the truck info: everything. year, mods, tire size, etc.

Most important question is always PMD: is it relocated off the Injection Pump? These boogers cause many hard starting symptoms.
Hot is NOT good on these trucks: over 210 is bad bad bad. Keep her cool.

My experience is that these trucks respond well to consistent love (and often $$).

 

[amc454]

Sorry, I am having trouble finding the signature deal. Under quick links I only see subscribe threads, site leaders, whos online, and contact popups. But Ill give you all the info you want here.

First, the truck is a 95 1/2 ton single cab long box with 145k on it. 4x4. Muffler has been cut out and dumps directly behind the door. The PMD was moved onto a heat sync bolted to the intake when I bought it, and after experiencing stalling problems, I bought another PMD and an extension cable and it now resides behind the grille where it can get lots of air flow. After moving the PMD, the alternator grenanded itself (literally the first start up after the relocation) So it has a brand new alternator as well.

Anything else you need to know just ask. Sorry I am new to this online forum deal, but I have always been able to fix my vehicle on my own... gas motors and our other diesels have generally made sense when they have issues. This acts up and I have no flippin idea what its doing or why, and I have worked more on this truck in the 1 onth and 1,000 miles ive owned it than I have worked on almost any vehicle I have ever owned... and I have owned a lot. I was hoping to make it a relaible drive for when I go back to school, 1100 miles away from home in Bristol TN, but at this point, i dont know if I trust it to drive to town and back.

 

[NVW]

Sorry, I am having trouble finding the signature deal. Under quick links I only see subscribe threads, site leaders, whos online, and contact popups. But Ill give you all the info you want here.

At the top right of the page is a link called "Settings", click on that then on the left side of the new page under "My Settings" you will see "Edit Signature".

 

[amc454]

Ok, so I think I got that signature thing figured. Thanks NVW.

Now to add a little more, I drove the truck to town and back today (about 10-12 miles round trip), not a hiccup. She fired right up cold, drove nicely, fired back up again hot after 15 minutes in the store, and drove home, not one complaint. No low coolant or any other idiot lights.

This is part of what is so frustrating about these trucks. It will act up, then run fine, and I will get my hopes up that it was just a fluke till it acts up again. But once again, hoping this was just a fluke. Got her too warm from running her to hard and she was being a little temperamental. If only I could be so lucky. I intend to put a few more miles on her today and we will see if she continues to be nice to be nice to me. Still open to any and all advice and help and anything else that people with more knowledge on this motor can tell me to help in making it a reliable and economical truck for the next year or so at least.

thanks in advance

 

[Chief915]

Check the lift pump.... it's on the inside of the frame on the drivers side, pretty much under the middle of the truck (from front to back).

Start the truck, then open the filter drain. The filter drain hose and t-fitting should be close to the thermostat housing. With the t-valve open, you should have a nice stream of fuel coming out and the truck should continue idling normally. If your lift pump is shot, or not running for some reason, you won't get any fuel from the filter drain and the engine will stall when the t-valve is opened.

Without the lift pump working, the truck will still run but will be low on power. Also after you "beat on it" for a little while (using a lot of fuel) you will kinda run out of fuel in the filter and to the IP, then the truck stalls. This would also account for your miss when you got it running again.

If the lift pump is not running, or you do not have fuel out of the filter drain hose, we will get into the things that could be causing that.

 

[amc454]

mmmmk... well the T-valve test passed.... sort of. I have done this test before when changing fuel filters and for other reasons, and I remember the flow being a lot faster than what it is now. That being said, I can open the T valve with no affect on idle, truck continues to run fine. Also, on a side note, I cannot hear the fuel pump when I hit the key. I remember distinctly being able to hear it before, and now I do not. The fuel pump relay was making a bit of a rattling noise when I pulled it out and inspected it, so i replaced it. However, I still do not hear the pump working.

While driving today, I put on 20 or 30 trouble free miles before it stalled again. This time operating temp was where it should be and no lights came on. It stalled 3 times in about a 10 mile span. When it stalled, I had to shut it off, turn the key back on and it'd fire back up and run normally. No problems since I replaced the relay, probably have put 5 miles on since then.

 

[NVW]

On the 95 it will pump while cranking but not with just the key on IIRC. Obd-2 will pump during the WTS.

You can put it in gear and turn the key to start to activate the LP.

 

[Brooklyn Tow]

Changed what "relay?"

 

[amc454]

The fuel pump relay.

Youll have to forgive me, not familiar with the meaning of IIRC or Obd-2.

As for the pump not activating hitting the key, I am unsure of this. When I did the T valve test once (before I was having this particular issue), I fired it up, let it idle for about 10 secs, and shut it off, when I shut it off the pump continued pumping fuel for nearly 10-20 more seconds, and had the distinct noise directly under the seat of the pump working. Maybe it was because I had started it to begin with like you said, and thats why it was working, and just assumed that when I hit the key it would pump. You say if I put the truck in drive with it off, and turn the key to the run position I should be able to hear the pump if its working? Ill give that a try.

 

[amc454]

Ok, I just ran outside, put the truck in gear, and hit the key... I could hear the pump. So... whats next.

 

[NVW]

IIRC= if I recall correctly

OBD-2= on board diagnostics-2

94-95 trucks were OBD-1, just a different system

The reason the fuel pumps after shut down is the LP is being powered by the Oil Pressure Sender until oil pressure drops.