GoAdv

Mortgage Payer

Got hot once - blew head gasket.
Exhaust pressure > water pressure around engine - stays too hot.

I'd start with a compression and leak down test before I pulled anything.
A head gasket and a skinny cut across the head is cheaper and faster than than another engine.

Stay OBD 1 if swapping.

DFlintstone

Agreed with Mortgage Payer 110%. Is it the inline 6 4.0? Those are nearly indestructible. Start with a compression test, (warm with all the plugs out, I do about five hits). Then add about two teaspoons of oil to each hole. A small vinyl tube is handy for that. Crank it i bit to get the oil into the rings, then take a second set of 6 numbers. This is a "wet" compression test, not a leak-down test. From those two sets of numbers a lot is revieled. IE: One alone came up a bunch, rings/cylinder there. Nothing changed much, rings are sealing OK. Two cyls together are low, head gasket. I'm sure posting those 12 # will get you some advice.

The combustion gas is like 2000K. Very little of it leaking into the water jacket will spike the temp faster than anything. If you top the expansion bottle and power/brake it (cap off, engine is hot), a little spew might be OK, but if the HG is really toast it will geyser!

These Jeeps rely on a decent fan clutch and shroud to move air normally. The Aux E-fan has a thermal switch and will come on at well over boiling, (218*....no mater), it it adds air flow . Mine comes on climbing a long hill slowly.

cruiser54

To answer your question:CRUISER'S MOSTLY RENIX TIPS

HO INTO RENIX SWAP

OCTOBER 31, 2015 SALAD 48 COMMENTS

This swap is easier than some will lead you to believe. And generally Pooh-poohed by those who have never done it. Those of us who have done it, like myself, will share with you the things that need to be done for a successful swap. Just think of it as swapping in a long block.

• XJ Cherokee and ZJ Grand Cherokee 4.0L engine blocks interchange.
• 2000+ TJ Wrangler and WJ Grand Cherokee 4.0L engine blocks interchange.
• YJ and 1997-1999 4.0L TJ blocks will interchange in XJ/ZJ
• XJ/ZJ blocks, and the 2000+ TJ/WJ blocks do not interchange without significant modifications.

TJ/WJ 4.0L Engine blocks underwent clean sheet design changes effective in the 1999 WJ Grand and 2000 TJ Wrangler. These blocks are not interchangeable with XJ/ZJ engine blocks. The reason is motor mount bolt holes and belt driven accessory mounting bolt holes are in different locations, or not present at all, TJ/WJ vs. XJ/ZJ.

Now that we know which engines we can use, let’s get down to business.

The HO and Renix have some differences but none that can’t be overcome very easily.

One running change was that the rear of the head was no longer drilled and tapped for the temperature gauge sender beginning in the 96 model year. The sender can be relocated to the threaded hole in the thermostat housing taken from an HO engine. You’ll have to extend the wire to that location. Some brave souls even drill and tap the HO head at the rear for the sender.

You will be using the intake and exhaust manifolds from your Renix, along with all your sensors and wiring. Since the intake ports of the HO are slightly different, you use a new Renix gasket. Exhaust ports are identical.

An alternative on exhaust manifolds:

As far as exhaust, you can use the Renix exhaust manifold and be fine.
If you want to use the HO exhaust manifold, you must go with an HO headpipe and screw your O2 sensor into that headpipe. Standard Renix harness is plenty long to do so.
A bung can be welded into the HO manifold to accept the EGR tube.

You will need to use your Renix distributor as it is different than the HO design. See Tips #12 – Setting Your 4.0 to #1 TDC and #13 – Distributor Indexing to be sure you get the distributor installed correctly.

The flywheel or flexplate from the Renix must be used so your CPS gets the correct signals. The valve cover from the Renix allows you to keep your CCV system intact and requires no modifications.

The HO block will have a plug in the coolant galley on the driver’s side of the block, closest to the front, which needs to be removed so your Coolant Temp Sensor can be installed in it’s place just as it is on the Renix. It requires a 5/16” square drive or a modified 3/8” drive that has been ground down to fit. Do this before installing the engine.

As for the knock sensor, which is located just above the oil pan on the driver’s side of the engine about mid way, all the blocks I’ve seen are threaded for it. If not, I’ve heard they may be drilled but not tapped. Tap the hole if that’s the case.



XJ: “Regular” (not Grand) Cherokees ’84-’01
ZJ: Grand Cherokee ’93-’98 (Gen1)
WJ: Grand Cherokee ’99-’04 (Gen2)
YJ: Wrangler ’87-’95 (Gen1)
TJ: Wrangler ’97-’06 (Gen2)

DFlintstone

Agreed testing would be first. A "wet-dry" test I mentioned is something anyone can do free. OBD-I or two though will swap however. How meany miles on that, and did it actually boil and spew, also how is the oil, milky or fine?