engine diagrams?

Does any one have tech diagrams for the 4.0 I6, its the coolant lines i am interested in, i have been searching here and the web but really stuggling to find any thing sufficient.

Cheers.

Hope these pictures help

Hallo Jeeper. 2 diagrams of coolanthoses of XJ's. Closed and open system.

click:

:yap: Cheers.

thanks guys but neither quite what i was looking for, i can't really see where the water feeds in and out of the block..

I am new to my XJ and have discovered coolant leaking at the back of the engine somewhere, its very difficult to see as it is right against the bulk head. I am assuming its the dreaded cracked head i have been reading about so much but want to be sure none of the coolant pipes are leaking first...

Hallo Jeeper. On the diagram #1102 is hot and is coming from the thermostat.
What Year is your Jeep?.
Is it with a closed system? Mayby your coolant pressure bottle is leaking.
When not , maybe the heater. :wave1:

The water feeds in and out of the block from the front of the motor. It runs into the block from the radiator through a hose behind the drivers side headlight. Then it runs out of the block at the top where those small hoses go to the firewall. (heater core) If you are leaking coolant from near the firewall, check the heater hose connections at the firewall, and check the heater valve. Part of that "T" connector, if you have one.

Unless you have a pressure leak squirting from a hose at operating temp onto the head, most likely AF at the back of the head is either a crack or leaking head gasket.

You could use a glass seal product to slow it down, but if it's still leaking after, well, time to break out the wrenches.

A-zone and OReilly may have a pressure tester to rent - or you could just drive it and then look to see what's leaking after a good warm up. Either way, simulating the same conditions will give a better view of what's going on and the source. As part of that procedure, you can power wash the engine and dust it with cheap talcum powder to find the source. The cleaned trail will run back to the leak point, or show a spray pattern.

TiRod said:

Unless you have a pressure leak squirting from a hose at operating temp onto the head, most likely AF at the back of the head is either a crack or leaking head gasket.

You could use a glass seal product to slow it down, but if it's still leaking after, well, time to break out the wrenches.

A-zone and OReilly may have a pressure tester to rent - or you could just drive it and then look to see what's leaking after a good warm up. Either way, simulating the same conditions will give a better view of what's going on and the source. As part of that procedure, you can power wash the engine and dust it with cheap talcum powder to find the source. The cleaned trail will run back to the leak point, or show a spray pattern.

Click to expand...

thanks but i am actually in the UK, i will however get the engine pressure tested, i am hoping for a simple gasket leak as the oil is very fresh and clean.

lewis

There is also a freeze plug on the back of the head that could be the source. Maybe pressure test the system & use one of those dental mirrors on a telescoping extension to try & see back there.

You can see it in this pic (ignore the red arrow)



fwiw the heads typically crack between cylinders (btwn 3&4 frequently) or in a chamber or passage and lead to exhaust bubbling into the coolant or coolant in the oil. To that point, since you say the oil looks good you should be able to get a test for exhaust or hydrocarbons in the coolant to cover the other type.

Also, for idle curiosities sake, this pic shows the two passages at the back of the head that permit the flow of coolant from the block up to the head for the journey back through the head & out the top hose. The passages are the two oblong ones at the far right that are mirror images of each other. There are a few other very small holes where coolant goes from bottom to top but most of what look like they should be big holes are actually mostly blocked by the gasket.



Another view of the two primary coolant block-to-head passages. An example of the mostly-blocked-by-the-gasket type of hole is in the upper right. I expect those are there to just stirr things up a bit in the corners of the head.

AHHHH now this is the sort of nugget of info i hoped might come up, what exactly is a freeze plug??

In Kimmel's pic above you can see the series of round "discs" sometimes they get corroded and begin leaking. From what I've read some are simply plugs from the casting of the block and others provide a "safety valve" in the event the block freezes. I can't say which are which on the 4.0 or even if this info is completely valid, I have helped change one on a 4.0 and it was relatively easy :anon:

infocus said:

thanks guys but neither quite what i was looking for, i can't really see where the water feeds in and out of the block..

I am new to my XJ and have discovered coolant leaking at the back of the engine somewhere, its very difficult to see as it is right against the bulk head. I am assuming its the dreaded cracked head i have been reading about so much but want to be sure none of the coolant pipes are leaking first...

Click to expand...

There should be four rubber hoses attached directly to the engine:

The water pump has a hose coming from the radiator - this is the point where coolant is introduced into the engine block proper. The water pump also has a nipple that has a smaller hose connected to it - this is the coolant supply for the cabin heater (flows out to the heater core.)

Water then flows through either the heater core or the engine block - and makes its way to the thermostat housing (front of cylinder head.) This has both the hose for coolant return to the radiator and coolant return from the heater core fitted to it, and that closes both loops.

The heater plumbing itself can vary, and there is usually a heater control valve plumbed into the heater hoses (deleted on later models, ca. 1999 I think.)

The simplest ways I've found to check for coolant leaks without tearing everything to bits:

1) Check all points where a coolant leak is possible for a white residue. This means anywhere the hoses attach to fittings, the hoses proper, the water pump fittings, the thermostat housing, and around the front, rear, and left side of the cylinder head (as mounted.) (The cylinder head does not have coolant passages on the right side as mounted - the only fluid that passes through there is oil. Either up through the pushrods, or drainback form the cylinder head.)

2) If you do not see any white residue anywhere, start the engine and let it idle. This is probably the quickest way to get the coolant up to operating temperature. Using a bright flashlight (preferably one with a fairly narrow beam as well,) cast about underhood and look for a small plume of steam - the light will cause it to show up better in anything less than full daylight. Once you find the plume, you can follow it down to the source.

Note that it is possible to have a coolant leak from the head gasket without losing compression as well, so be sure to check that junction.

The "cracked head issue" you've heard about is the 1999-2000-(early)2001 #0331 cylinder head castings - we escape the first year by still using the #0630 head (if you don't have distributorless ignition, you don't have the #0331 head.) This is a crack between the #3 and #4 cylinders, and it allows coolant to bleed into the engine oil sump. However, this crack typically does not result in an external coolant leak.

Jeepsloth said:

In Kimmel's pic above you can see the series of round "discs" sometimes they get corroded and begin leaking. From what I've read some are simply plugs from the casting of the block and others provide a "safety valve" in the event the block freezes. I can't say which are which on the 4.0 or even if this info is completely valid, I have helped change one on a 4.0 and it was relatively easy :anon:

Click to expand...

Half marks. They're commonly referred to as "freeze plugs" - but also "welch plugs" (don't know where that one came from) or "core plugs" (which is technically correct.

They are present because the sand cores used to form the mould have to be flushed out after the block has hardened - and these are the ports where that happens. After flushing, they are bored to size and the plugs inserted. They probably picked up the moniker "freeze plug" because they were in the coolant jacket and people thought that was what they were - they're not (I've seen blocks frozen - and cracked! - with the core plugs still neatly in place.)

It should be noted that, as processes improve, the core plugs are gradually being eliminated in the interest of making the block stiffer. The new Hemi, for instance, does not have core plugs...

infocus said:

AHHHH now this is the sort of nugget of info i hoped might come up, what exactly is a freeze plug??

Click to expand...

Like Jeepsloth said they are the round shiny plugs in the holes on the side of the block and the shiny one on the back of the cylinder head above the torque converter.

That's the one I was thinking might be the source of your leak. If you look in the engine compartment you'll see it's difficult to directly observe the back of the head which is why the mirror on a stick might be useful.

As far as replacing that one specifically if it is the problem I don't know, you'll probably have to remove the head. Although it might be possible to get at it by suspending the engine from a crane, removing the motor mounts, possibly removing the cooling fan and other bits off the front of the motor, maybe the radiator & letting the motor down enough to get back there.

Usually you have to hammer one side of the plug with a blunt punch, pipe or socket extension or similar so that the pug rotates in the hole kind of like a door & you can pull it out. Clean the opening & hammer the new one in using a socket or pipe about as big as the dish portion of the plug. You have to pound it pretty good so that's why removing the head may be the way to go.
Some people put a bead of water safe RTV on the inside edge of the plug, some people say it's not necessary. I used it & no harm so far.

Here's a bunch of example pictures but any auto parts store should have them. You'll notice that the sets for the 6 cylinders there's one odd plug. I think that's the one for the back of the head, possibly a different size.

http://motors.shop.ebay.com/_Car-Tr...romfsbZQQ_fxdZ1QQ_sopZ1QQ_trksidZm270Q2el1313


You can also buy a heating element unit that replaces one of the side plugs. Makes for a nice warm winter start & fast heat. Wish I'd taken the time to put one in.

http://motors.shop.ebay.com/_Car-Tr...romfsbZQQ_fxdZ1QQ_sopZ1QQ_trksidZm270Q2el1313

thanks so much for the help guys

5-90 said:

There should be four rubber hoses attached directly to the engine:

1) Check all points where a coolant leak is possible for a white residue. This means anywhere the hoses attach to fittings, the hoses proper, the water pump fittings, the thermostat housing, and around the front, rear, and left side of the cylinder head (as mounted.) (The cylinder head does not have coolant passages on the right side as mounted - the only fluid that passes through there is oil. Either up through the pushrods, or drainback form the cylinder head.)

2) If you do not see any white residue anywhere, start the engine and let it idle. This is probably the quickest way to get the coolant up to operating temperature. Using a bright flashlight (preferably one with a fairly narrow beam as well,) cast about underhood and look for a small plume of steam - the light will cause it to show up better in anything less than full daylight. Once you find the plume, you can follow it down to the source.

Note that it is possible to have a coolant leak from the head gasket without losing compression as well, so be sure to check that junction.

The "cracked head issue" you've heard about is the 1999-2000-(early)2001 #0331 cylinder head castings - we escape the first year by still using the #0630 head (if you don't have distributorless ignition, you don't have the #0331 head.) This is a crack between the #3 and #4 cylinders, and it allows coolant to bleed into the engine oil sump. However, this crack typically does not result in an external coolant leak.

Click to expand...

1/ i had gone through all this as soon as i discovered the leak which is why i came here to ask questions.

2/ I'll do this today.

My jeep is a 2001 model which i am pretty sure has distibutor less ignition.

Lewis

infocus said:

thanks so much for the help guys



1/ i had gone through all this as soon as i discovered the leak which is why i came here to ask questions.

2/ I'll do this today.

My jeep is a 2001 model which i am pretty sure has distibutor less ignition.

Lewis

Click to expand...

Easy enough to tell - if you have COP/DIS (and the infamous #0331 head,) you'll see a rail overtop of your spark plugs. It will have three "warts" on it (three coils - each fires two plugs,) and there will be three or four screws (I don't recall...) that hold it to the cylinder head.

Question - are you losing coolant on the ground, does your oil look like a chocolate milkshake, or are you just losing coolant? I probably should have asked that earlier...

Yep, my engine does have the coil bar you described.

Yes the coolant leak is ending up on the ground rather than going through the engine, i am fairly sure it is not getting into the oil as it was changed about 6-7 weeks ago and i have been checking it constantly and it still looks perfect.

infocus said:

Yep, my engine does have the coil bar you described.

Yes the coolant leak is ending up on the ground rather than going through the engine, i am fairly sure it is not getting into the oil as it was changed about 6-7 weeks ago and i have been checking it constantly and it still looks perfect.

Click to expand...

OK - so it's not the "#0331 Crack Issue" - that's a totally internal leak.

Check gaskets, check hoses, check the core plugs. Use a mirror-on-a-stick to see, well, pretty much all of them. There is one you won't be able to see - it's inside the bellhousing - but it's the back of the cam bore and does not seal coolant, so it can be ignored.

One more thought. If you have access to a UV light you could try some of this leak detection dye. Looks like they sell a pack of 6 bottles for between $17 - 20 USD but maybe you can get them individually at an autoparts store.

http://www.tracerline.com/faq.html

Add to coolant, run the engine then shine the UV light around to see where the leak is coming from. Can help when the leak is minor enough that you can't really tell exactly where the source is but can see the result on the ground.

UV lights: http://www.blacklight.com/

Arachnid™ A14
Ultra Violet Scorpion
Class Blacklight
Only - $19.99

Probably a lot of scorpions in the UK you never see because you don't have one of these!

Let us know how it turns out.

just spent a half hour with the engine running at temp trying to spot leak, no luck, couldn't see any steam but it does seem damp at the rear end of the engine cover... would the gasket between the top of the head and the cover be a possible leak spot?

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here is where the leak is visable as a steady dripping..

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