M1009 radiator Issues

[JamieM1009]

I recently replaced the radiator in my M1009 & all seemed to go well. I've bled the system and had it running fine with the blower nice & hot and just a little bit of water going in to the expansion tank. Then i changed the temp sender unit & installed a gauge on the dash. Since doing this i've had a couple of moments where the blower was cold but the gauge rose to over 220 Degrees and then suddenly the gauge dropped to 180 & the blower went hot as it should be. It also pushes some water out in to the expansion tank but not loads. Once its done that the heater stays warm & the temp reads as it should with it sitting around 185 degrees and doesn't overheat at all.

Can anyone help me to figure out why it would do this? It seems like its sucking in some air and then once the stat opens the water circulates correctly and the air is expelled in to the tank with some of the water.

Should i have used some tape on the thread of the new sender unit? Could it be sucking the air in from there?

The trucks runs perfectly & starts perfectly apart from this issue its all good.

Any help would be great

 

[MarcusOReallyus]

• That's not a particularly useful thread title. A good thread title attracts the interest of people who have special expertise in your particular problem, AND makes it easy for future readers to find solutions to similar problems. The whole point of this forum (and every forum like it) is to get assistance, so just "need assistance" might as well be gibberish for all the good it does. Wait... No, gibberish would attract more interest (just out of curiosity) and increase your chances of getting assistance.

• When you bleed the system, park the truck uphill and make sure your heater is wide open. It's very easy to trap air in the system.

• Yes, it's good to use sealant tape, and you might be sucking air in there.

 

[Adrian A]

There is still air in the system. Run the defrost vent and warm the truck then rev the engine a bit. This generally works. Make sure the thermostat is open to circulate. If there is no moisture anywhere you will not likely be sucking air into the system as it is pressurized when at operating temp.

 

[JamieM1009]

• That's not a particularly useful thread title. A good thread title attracts the interest of people who have special expertise in your particular problem, AND makes it easy for future readers to find solutions to similar problems. The whole point of this forum (and every forum like it) is to get assistance, so just "need assistance" might as well be gibberish for all the good it does. Wait... No, gibberish would attract more interest (just out of curiosity) and increase your chances of getting assistance.

• When you bleed the system, park the truck uphill and make sure your heater is wide open. It's very easy to trap air in the system.

• Yes, it's good to use sealant tape, and you might be sucking air in there.

There is still air in the system. Run the defrost vent and warm the truck then rev the engine a bit. This generally works. Make sure the thermostat is open to circulate. If there is no moisture anywhere you will not likely be sucking air into the system as it is pressurized when at operating temp.

Thanks for the reply, sorry about the thread title. I will ammend it & consider myself told.

There doesn't seem to be anything leaking out of anywhere but i will take the sender back out and put some tape around the thread as well just to be on the safe side.

I ran the system up to temp without the rad cap on & got as much air out as possible before putting the cap on & giving it a good run around. I thought i had got it all out as it seemed to run fine & the heater was hot but then the next time i used it the heater was cold & it did what i stated in my first post but maybe there was some air still trapped. Other than run it again without the cap on and give it another drive, is there another way to get the air out?

 

[MarcusOReallyus]

It's easy to keep air trapped in there. Putting the front end higher really helps. Of course, make sure you have it hot enough to open the T-stat, and have that heater wide open. Also, squeeze the upper radiator hoses a few times. Sometimes that frees some trapped air. Rev the engine periodically, and give it time! You don't get it done in 5 minutes.

I wouldn't run around with the cap off. I put the front end up on ramps and do it all right there. Do you have plastic car ramps available over there? They are really handy to have around.

http://www.northerntool.com/shop/tools/product_200510315_200510315

 

[JamieM1009]

It's easy to keep air trapped in there. Putting the front end higher really helps. Of course, make sure you have it hot enough to open the T-stat, and have that heater wide open. Also, squeeze the upper radiator hoses a few times. Sometimes that frees some trapped air. Rev the engine periodically, and give it time! You don't get it done in 5 minutes.

I wouldn't run around with the cap off. I put the front end up on ramps and do it all right there. Do you have plastic car ramps available over there? They are really handy to have around.

http://www.northerntool.com/shop/tools/product_200510315_200510315

When i ran it with the cap off it was running for about 25 minutes or so before i put it back on & went for a drive. It would push some water & a load of bubbles out the radiator, i squeezed the top hoses to get more out & then you could tell the T-stat had opened as the water level dropped & i had to top it back up. I let it push the bubbles and water out & the level drop 2 or 3 times & then put the cap on & drive. Should i just do it once, then put the cap on & drive? I have some steel ramps i can use to get the front end high.

 

[Adrian A]

I wouldnt take anything apart yet. Just use the suggestions from those posted and be patient. Dont drive it hard as to overheat it. I would put the radiator cap on an rev it to circulate the water real good. Then let it cool and check it after it has cooled off.

 

[JamieM1009]

After letting it cool I checked the level & it had gone down by quite a bit so there must have been quite a lot of air that was trapped & had made its way to the top of the rad. I'll put the front up on ramps tomorrow and attempt to bleed it again with the cap off, let it heat up & the T-Stat open then put the cap back on & go for a drive. Fingers crossed that will sort it.

One question i would ask, is it normal that when you have no pressure in the system & you have just put the rad cap back on, you squeeze the top hose & you get bubbles in the expansion tank, but when the system is under pressure you dont really get any bubbles in the tank, maybe the odd 1 or 2? Is this normal or is the rad cap faulty? It does hold the pressure & the hoses do get hard.

Thanks

 

[Adrian A]

Your good. Just give it a few cycles and keep an eye on it.

 

[JamieM1009]

Your good. Just give it a few cycles and keep an eye on it.

Thanks, i'll let u know how i get on.

Thanks to everyone else who replied....

 

[JamieM1009]

So i bled the system 2 days ago. I had it up on ramps & let it run with the cap off for about 30 minutes with all the bubbles coming out, the T-stat would open, the level drop and i then topped it up. I did this about 3 times & then put the rad cap back on & went for a drive. Drove well, no issues, no overheating & it only pushed a bit of water in to the expansion tank.
I took it out yesterday & it heated up fine, heater warmed up all fine & temp gauge sat at around 180-190 with no overheating issues at all, small amount of water went in to the expansion tank but the level only rose by about 2cm. However I took it out today & the heater did not warm up until the temp gauge rose to about 230 (after 5 minutes of driving), at which point the gauge suddenly dropped down to about 170 (I guess the T-stat opened). After this it ran fine, temp gauge sat at around 180-190 with little movement, the heater was warm and it pushed out about another 1cm of water in the tank (not much really).

Question is why would it be fine one day & then the next day it suddenly shoot up to 230 on the gauge before quickly cooling(in about 10 seconds) & then the heater getting hot???

I also noticed that when I was bleeding it, after the T-stat opened & the water level dropped there wasn't much coming out of the heater hose that goes in to the rad, it seemed to be a trickle. I know that it doesnt really push a lot of water around unless it is at the correct pressure but is this normal or is it a symptom of a failing water pump?? If so would this cause the cold heater issue, etc??? The outlet form the heater core is no where near as hot as the inlet hose. COuld it just be blocked and the free's it self?



Any ides or help would be great.

 

[JamieM1009]

I've read a few old posts on here & am leaning towards a possible blocked heater core? With the limited flow coming back from the heater core in to the rad & the issue only being from cold start up, i was thinking how likely is it that the core is blocked & it needs the pressure to build up in the system to force the coolant around and past any blockage in the core??? Would this be why the temp gets up to about 230 & then suddenly drops?? Is the water not flowing but getting hot where it is until the T-stat opens & then more coolant just forces it past the blockage??

 

[cpf240]

Try running water through the heater core with a garden hose. Another test would be to bypass the heater core and see if the rest of the temp conditions are back to normal.

 

[JamieM1009]

So I've been using the truck and although it was fine for a few days its playing up again. Its only reading hot on the gauge for a few minutes and then the stat opens and everything is back to normal (180-190) with some water going in the expansion tank. Any one got any ideas? Its not overheating while I drive it so can't be too bad. it doesn't draw the water back out of the expansion tank as it cools, is this normal? There isn't any leaks anywhere. How much water should it put in the expansion tank? It also holds the pressure in the cooling system for a couple of day after use, is this normal?