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1999 4.0l Jeep, freeze plug and coolant issues


 
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Spule 4
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Joined: 11 Sep 2007

PostPosted: Tue Sep 11, 2007 7:01 pm    Post subject: 1999 4.0l Jeep, freeze plug and coolant issues Reply with quote

All:

I Joined your forum to see if anyone could help me help a friend with his 1999 Jeep Cherokee with a 4.0l inline six.

The truck has always run a bit hot. Then, last summer, the Jeep's coolant turned rusty. At this time, he replaced the radiator, thermostat, cap and had the system flushed, adding green coolant. A year later, it has done this again (rust colored), and now, the freeze plug on the back of the head is leaking. This was beyond his skills, so now it is in my driveway Shocked .

I am interested in why it has made its coolant rusty again. In all my years of working on cars (99.99999% of this was on imports), I have never seen an engine do this once it has been flushed. A friend of mine with much more US car experience in his shop feels that it is drawing air into the cooling system somehow?

Two, I assume the head has to come off to replace the plug (and it appears best to do the plugs on the driver's side of the motor too while at it. If there is another way of doing this.....but I think I know the answer.

Three, if the head does come off, what is the 12pt socket size (and is it metric or std) so I can buy the correct socket for the job.

Thanks in advance for any replies-

Garrett
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Brad The Best
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Joined: 14 Jan 2007
Location: Kamloops B.C Canada

PostPosted: Tue Sep 11, 2007 7:14 pm    Post subject: Reply with quote

to replace all the freeze plugs you will actually have to pull the engine and remove the flex plate , there are two behind it .

the frost plugs usually rust from the inside and look good from the outside , if your having a problem replace them all . they come in a kit anyway .

i have a 4.0 block sitting in my garage on a stand , its a 89 with 300 000 on it . and i can tell you the inside is a little rusty and full of sand from when they cast the block, i only found the large amount of sand at the back of the engine i guess ti accumulated there and stayed put . silly engine manufacturer couldn't even clean out all the sand .

did it ever go through coolant ? or burn coolant ? maybe it had a pretty watery mixture with crappy anti freeze .

what has this jeep been through ? has he owned it from day 1 ?
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monkeyman3875
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Joined: 06 Jul 2005
Location: Charlotte, NC

PostPosted: Wed Sep 12, 2007 12:13 pm    Post subject: Reply with quote

I had the same thing happen last summer. The job's not really as hard as it sounds. My brother-in-law and I did the entire job in a weekend. It's tough, just lengthy. The whole thing is outlined in a FSM you just need to make sure everything is clean when you put it back together. I can give you a rough idea.

1. Disconnect battery and drain engine coolant.

2. remove air cleaner assembly

3. remove cylinder head cover.

4. remove capscrews, bridge and pivot assemblies and rocker arms (keep them in order)

5. remove push rods (keep them in order)

6. remove serpentine belt

7. remove bolts from AC compressor (if equipped) mounting bracket and set compressor aside. loosen bottom bolt but don't remove

8. disconnect power steering pump bracket, set pump and bracket aside DO NOT DISCONNECT THE HOSES

9. Perform fuel system pressure release

10. remove fuel lines and vacuum hose

11. remove intake and engine exhaust manifolds from the cylinder head

12. disconnect ignition wires and remove spark plugs (mark each for easy replacement)

13. remove ignition coil and bracket assembly (i don't think i did this one)

14. remove engine cylinder head bolts. remember which you took out of the driver's side front of the block.

15. remove engine cylinder head and gasket (clean both sides very well)

16. put towel or something in the cylinders to keep them clean.

17. use a punch on one side of the plugs to spin them then pliers to get them out.

18. Use very large socket and mallet to replace plugs (might as well do all of them)

19. Clean everything very well, and if the jeep has ever overheated, make sure you have the head checked for warping while it's still off the jeep (I forgot to do that and had to do it again to get the head machined)

20. Put it all back together.

There you have it, very straight forward. There are more precautions to the job that are listed in a manual, but what's above is pretty close to it.

When my brother-in-law and I did the job, I had no experience apart from tire rotations and oil changes, and my brother-in-law had never dug into an engine. Overall, not a very difficult job as long as you pay attention to detail.

GOOD LUCK!!
_________________
-1997 Stock XJ
-4.0 L
-4-speed automatic
-130k Miles (and counting)-> let me know of any preventative maintenance you guys can think of. PM me.
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Spule 4
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Joined: 11 Sep 2007

PostPosted: Wed Sep 12, 2007 4:19 pm    Post subject: Reply with quote

Brad The Best wrote:
to replace all the freeze plugs you will actually have to pull the engine and remove the flex plate , there are two behind it .

the frost plugs usually rust from the inside and look good from the outside , if your having a problem replace them all . they come in a kit anyway .

i have a 4.0 block sitting in my garage on a stand , its a 89 with 300 000 on it . and i can tell you the inside is a little rusty and full of sand from when they cast the block, i only found the large amount of sand at the back of the engine i guess ti accumulated there and stayed put . silly engine manufacturer couldn't even clean out all the sand .

did it ever go through coolant ? or burn coolant ? maybe it had a pretty watery mixture with crappy anti freeze .

what has this jeep been through ? has he owned it from day 1 ?


Street use only, been here in the south its whole life, 100K, one previous owner about four years ago, no previous SH on the truck unfortunately from before. Not a coolant user, just liked running hot, plugged the first radiator and the heater core (which I flushed later after the shop he took it to did not flush it).

With this and some other reading on the net about the other plugs, we are going to extricate the motor from the truck and do all the plugs instead of pulling the head, thanks!

Garrett
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Spule 4
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Joined: 11 Sep 2007

PostPosted: Wed Sep 12, 2007 4:25 pm    Post subject: Reply with quote

monkeyman3875 wrote:
I had the same thing happen last summer. The job's not really as hard as it sounds. My brother-in-law and I did the entire job in a weekend. It's tough, just lengthy. The whole thing is outlined in a FSM you just need to make sure everything is clean when you put it back together. I can give you a rough idea.

GOOD LUCK!!


Thanks, very detailed there. I have pulled more heads than I care to think of. Just really did not want to do this one if I did not have to, and now it appears I do not!! Razz Razz

The motor looks about as easy to pull as a Volvo B20/30F from the 1970s, just a big hunk of cast iron (even tubular headers like my long dead 1968 Volvo).

As for the Jeep motor itself, I forgot, I do have some experience with these motors back in the 1980s, mostly customers runing them nearly dry on oil, but even that did not kill them!

Garrett
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Brad The Best
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Joined: 14 Jan 2007
Location: Kamloops B.C Canada

PostPosted: Wed Sep 12, 2007 6:56 pm    Post subject: Reply with quote

the only crappy thing is depending on the transmission they put two external torque cap screws at the top of the bell housing , i didn't have them so i took one of the torque bolts off my uncles tow hooks on his yj and welded them in a socket and wala worked like a charm .

you might just want to buy a set , i think it was a #12 or something . the engine is easily pulled in a xj .
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Spule 4
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Joined: 11 Sep 2007

PostPosted: Thu Sep 13, 2007 2:29 pm    Post subject: Reply with quote

Brad The Best wrote:
the only crappy thing is depending on the transmission they put two external torque cap screws at the top of the bell housing , you might just want to buy a set , i think it was a #12 or something . the engine is easily pulled in a xj .


Thanks, I will look into that before I get into the Jeep.

Garrett
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Spule 4
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Joined: 11 Sep 2007

PostPosted: Sat Sep 15, 2007 3:00 pm    Post subject: Reply with quote

Brad The Best wrote:
the only crappy thing is depending on the transmission they put two external torque cap screws at the top of the bell housing , i didn't have them so i took one of the torque bolts off my uncles tow hooks on his yj and welded them in a socket and wala worked like a charm .

you might just want to buy a set , i think it was a #12 or something . the engine is easily pulled in a xj .


Yes, they are there. Went underneath to get the driver's side one. The passenger one was tough no matter what. Then, my helper asks "gee, what if we remove the shifter?"

So sitting in the seat through the floor, a LOT easier to do it this way!

Garrett
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