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help with air in system PLEASE

6K views 27 replies 10 participants last post by  Jeepyard 
#1 · (Edited)
HELLO
my 2004 (54) grand cherokee sport has just had a new radiator and since then the temp gauge seems to go up at random times whether i am driving fast or slow so i then thought i needed a new thermostat so i went and replaced it but now the temp gauge is going hot and cold and there is no heat coming from the heater. I am now thinking that there is air trapped in the radiator or in the pipes some where but do not have a clue how to remove it as i can not find any bleed screw so could someone please help me fix my problem as its doing my head in lol. thanks in advance :s
 
#2 ·
4.0L or V8?
 
#4 ·
Sorry then I wont be much help. There is a bleed plug to remove when filling the system on the V8, but I dont think the 4.0 has a plug.
 
#7 ·
it needs burped....

remove the radiator cap, start the engine and let run with the heat on for 15 minutes.
If you cannot see the coolant, then the level is low. Pour in anti-freeze to top the coolant level off. The coolant in the radiator will bubble and pop. Keep pouring in coolant to the radiator till the level stays full. Tighten the cap back on the radiator when the level stays full. Give the radiator a window of five minutes of running, after you top it off, to ensure all the air is bled out.
 
#8 ·
ok i have done this about 5 times and have watched bubbles come up but its still the same, no heat blowing and the temp gauge keeps going hot and cold. I was going to start again and drain all the coolant out but the damn plug on the radiator is made of plastic and i have now snapped its wings off trying to undo it.:mad:
 
#9 ·
Stupid question...but is it possible the stat was put in backwards? I'm pretty sure it's physically possible.

or maybe the new stat is faulty?
 
#10 ·
the stat is defiantly in the right way i took a picture before i took it out just to make sure also when i bought the stat the guy at the counter just typed in my reg and give me what the computer said but on the box it did say ford now im guessing that that is ok as some cars can take the same parts i hope
 
#13 · (Edited)
Yeah, you probably have air in the system. There shouldn't be any reason to burp the system since it has an overflow tank. According to WJJeeps (this is what I did when I flushed my system a couple weeks ago):

1. Tighten the radiator draincock and the cylinder block drain plug(s) (if removed).

2. Fill system using a 50/50 mixture of ethyleneglycol antifreeze and low mineral content water. Fill radiator to top and install radiator cap. Add sufficient coolant to the reserve/overflow tank to raise level to FULL mark.

3. With heater control unit in the HEAT position, operate engine with radiator cap in place.

4. After engine has reached normal operating temperature, shut engine off and allow it to cool. When engine is cooling down, coolant will be drawn into the radiator from the reserve/overflow tank.

5. Add coolant to reserve/overflow tank as necessary. Only add coolant to the reserve/overflow tank when the engine is cold. Coolant level in a warm engine will be higher due to thermal expansion. To purge the cooling system of all air, this heat up/cool down cycle (adding coolant to cold engine) must be performed three times. Add necessary coolant to raise tank level to the FULL mark after each cool down period

http://www.wjjeeps.com/service/cooling.htm#DRAIN40
 
#14 ·
If it was your water pump I would think you'd be overheating and never seeing cooler periods while driving. It would likely leak or seize too...and you'd be able to see if that was the case.
 
#18 ·
what is the cylinder block drain plug for can i use this instead of the plug on the radiator
Don't worry about that. While the engine is cool, fill up the radiator and overflow tank with coolant/water mixture. Then turn your engine on, heater on, and let the engine run up to normal temp. Then let it sit and cool back down (a few hours). Check on it every 15-20 minutes and top off the overflow tank to keep the level at the FULL mark.

Once it's completely cooled down, make sure the overflow tank it at the FULL mark and start the engine again (with the heater on). Let it warm up to normal temp again and turn it off. Again, keep an eye on the overflow tank while it cools and top it off when needed. Then do this once more and you should be fine (3 times total).

Basically what it says on WJJeeps but you don't worry about step 1.
 
#16 ·
The cylinder block drain plug is a plug in the side of the engine that allows coolant to flow out of the engine block only. It will not drain any coolant that is in the radiator.
 
#17 ·
Be VERY careful messing with that cylinder block drain plug. I have no personal experience but I know I've read on more than one occassion where people have had a hell of a time getting that off...snapping tools, breaking the plug itself (then you're screwed unless you buy one in advance), etc.
 
#20 ·
Not sure what you've got in the UK, but around here that's a relatively standard part. I think I got one at a local Napa or Federated Auto Parts store. It's somewhat universal...best to take yours in to a parts store to find a match. IF you haven't broken it yet, you're really better off just pulling the lower hose off to drain. That draincock is a pain in the a$$.
 
#24 ·
Have you replaced the radiator cap? The cap has a check valve in it that allows the coolant to pass back and forth from the overflow tank to the radiator. If the check valve is defective it may not allow the coolant to move back and forth. This can also help hold trapped air which usually show up as the engine cools and the upper radiator hose collapses because the check valve is closed and will not allow overflow coolant to be drawn in. As the engine heats up, it should push air out thru the cap and into the overflow tank which is vented allowing the air to escape. Eventually, the air will be pushed out and coolant will completely fill the engine system. This could be your problem!
 
#27 ·
Grab and squeeze the top hose with hot engine running use a rag or glove to insulate) and see if you can feel the flow into the radiator. You should be able to feel the circulating coolant. When H20 pumps fail, it can be the bearing ( they howl and squeal) or leak through the seal at the front. However, I've removed suspect H20 pumps where the internal impeller ( plastic & metal) had lost its press fit to the pulley driven pump shaft and was freewheeling and not being driven by the belt. Avoid the budget H20 pumps; buy A grade gear on all things cooling system-just not worth the 'over-heating' risk and ensuing wallet- ache. Why was the radiator replaced? Was it possible it wasn't the issue and it was the pump? Good luck with the diagnostics and keep us apprised of any observations.
 
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