I have a question about my cylinder head.
I have a 1996 xj 4.0

had a leaking Welch plug tried fixing it temporarily thought I could get away with taking it out patching the hole and re inserting it with rtv.
Test drove it and the old plug popped out causing car to over heat.
I turned off the car examined the issue. As I was only up the road up a hill. I coasted down. Turned car on to get me back home probably 1 min of driving over heated. If I didn’t have my kids freaking out I would’ve waited hence why I just drove back home..

Looked around apparently it’s ok to turn on engine without coolant as long as it doesn’t get hot.
I turned the car on next day to get it in the garage to put new Welch plugs in.
car started first go, no strange sounds or white smoke.

Now the new plugs are in waiting for the manifold gasket to arrive to build it up and re fill coolant.

my question is, how long can this 96 block be on while over heated.
I am terrified that I may have done damage to the head or head gasket.

haven’t found any milky oil or and thing like that and the head looks sealed on well doesn’t seem warped.

How strong are these engines?
ive read people say they drove it pinging on hot for 10 mins on a track before they could pull up and cut the engine and they’re 4.0 lived to see another day.

 

imo, the easiest way to check is allow vehicle to warm up while idling with radiator cap off, fill radiator neck to the top, watch it for a few minutes.

if the head gasket is damaged, bubbles will be usually be observed

iron is forgiving, you should be ok if 1 minute is all you truly did

 

Ok thanks I’ll try that. Currently still is not back together I’m waiting for the manifold gasket.
I will have to burp the system I guess first and then let it run and observe it once it seems it’s all burped.
ive heard these iron blocks are strong. If worst case it is a head gasket that’s ok it’s a $50 repair I have all the tools so let’s hope it’s all ok.

 

If you have all the manifolds already off....thats more than half the battle to get the head off..might as well just change out the head gasket...Felpro makes a decent HD gasket thats fairly cheap. I find getting the manifolds off is the hardest part of a head change. I have built several motors, I am unfamiliar with the term welch plug

 

Thanks mate. Your right I think I’ll actually buy the gasket set and do all of them even rocker cover which is leaking too. (It’s a jeep)

and today you learn something new my friend. Welch plug / welsh plug is another name for Freeze plug or expansion plugs. Although a lot of people say these are designed for expansion of frozen coolant in the block they started calling them freeze plugs out there. But here where there is no snow no body calls them freeze plugs but rather Welch plugs.
I am in Australia and we are backwards so don’t ever think what we call things is right 😂

 

I understand now....you took off the manifolds to get access to the welch plug..got it. If you do take off the head remember the frontmost drivers side ,For left side steering ,headbolt ...#11 i think goes through the water jacket and needs to be coated with high temp thread sealer all the way up the threads and it gets 10 lbs LESS final torque than all the rest

 

awesome thank you. Thankfully I have the Haynes manual and I studied that part just incase I’ll have to do the head gasket. It really does seem easier the. The manifold but in saying that I actually didn’t have too much issues with the manifold. I have skinny little arms and they fit in ti get the harder ti reach spots.

I have to move 2 hours away and am on a dead line.
I really wanted to attack any other issue once the move is done. So I’m hoping the freeze plug repair is all that’s needed and she starts and holds temp.

ideally I wanted to buy a gasket set and replace the rest of the plugs and do every gasket.
I just hope my over heat didn’t do the head gasket or head.
it was 1 min maximum 2 min of running peak temp.
remiving the manifold it looks like there’s no leak from the outside.
and upon start up to move it on the drive way before putting in the new plug, it seemed ok.

I just need to wait for my manifold gasket to get to me to build it and run it and see what it does

 

Ok no issues...good luck with everything

 

You say that like it's a good thing. It's not. Both Haynes and Chilton have just enough good info in them to fool you into thinking they are trustworthy. They are not. They also have a lot of bad info in them.


That doesn't mean anything at all. Drain your oil and see what's in there.

 

you mean to check for milky residue?
coolabt and oil mixed together?
I checked the dip stick it wasn’t milky.
would this suffice?
more draining oil is a better way of checking?
thing is I don’t have enough for an oil filter or enough time to wait for a new one. Literally need to be out of this house next week and still haven’t even got my manifold gasket.
I have oil to put in it again though. Could I drain it and refill it without changing the filter temporarily until the move is done?

 

Nope. Many hqave missed coolant in their oil by that method.


Much better.

Yep. If the oil is not contaminated with coolant, there's no problem with using the same filter. Just leave it where it is. If there's coolant in it, you have a very different problem. You need to KNOW either way.

 

yes your right. Head gaskets only like $50 so might as well change it now while the manifold is off.
hoping the oil is ok. Have a feeling it will be as it didn’t run hot for long.
Here’s hoping!
I’ll find out today