Cracked Jeep 4.0 head

Chad Culbertson · **Posted:** Sat Nov 07, 2015 10:40 pm

The jeep is running again with a fresh rebuilt ebay cylinder head. It's running great but something is obviously wrong with the cooling system. That wasn't really much of a surprise since heads don't just crack on their own generally. Something caused this problem to start with.

The fan clutch was bad for sure, you could stop it with a stick and free spin it at idle even with the temp gauge showing 210*. Replaced that and it's moving noticeable more air now, however still overheating. Next step is the water pump, if I get the rpms up 2k-3k it actually starts cooling down and the upper radiator hose gets noticeably more warm. I suspect the water pump impeller might be toast given the amount of corrosion I saw in the system. I probably should have just replaced it while the head was off, especially since a new one is only $30.

The rear differential is pretty noisy going down the road at 60ish mph, i'm going to change the fluid and put some heavy duty gear oil in it, but I doubt that makes it much quieter. Going to play that by ear and see what happens. Jeep axles are a dime a dozen, so not too worried about that.

Roger McDaniels · **Posted:** Sat Nov 07, 2015 11:18 pm

thermostat?

Chad Culbertson · **Posted:** Mon Nov 09, 2015 12:11 pm

Roger McDaniels wrote:

thermostat?

Put a brand new one in with the new head. Thinking water pump or radiator at this point. I really should have just put a new pump on with the head, they're only $30. The coolant I dumped out originally wasn't very clean looking so I probably won't be surprised if the radiator is clogged, but since the waterpump is of unknown age and miles I think it makes sense to just go ahead and replace it also. If the old one looks ok impeller wise then i'll know the radiator is probably clogged up. Before long i'll start to run out of things to replace, pretty sure this problem is likely what lead to the original head cracking.

Chad Culbertson · **Posted:** Tue Nov 17, 2015 12:05 am

For future reference, get the air out of the head on these things is a major PITA. If the thermostat you buy doesn't have a jigger pin or bleed hole, drill a 1/8" one lol.

I wound up replacing the water pump and radiator mainly because I had no idea how old they were but also in the hopes the thing would run cool.

Still couldn't get it to stay cool and it was circulating coolant through the radiator properly. Took the t-stat out and it runs at the temp expect, cold. So cold the heat won't work, etc. The t-stat checks out in boiling water just fine so my only guess now is a air pocket keeping it from opening. Apparently the trick is to have a 1/8" hole in the rim positioned at 12 o'clock to allow the air to bleed out.

If that works so well why don't they all come with that bleeder hole? geez. lol.

Chris Halweg · **Posted:** Tue Nov 17, 2015 10:58 am

Chad Culbertson wrote:

For future reference, get the air out of the head on these things is a major PITA. If the thermostat you buy doesn't have a jigger pin or bleed hole, drill a 1/8" one lol.

I wound up replacing the water pump and radiator mainly because I had no idea how old they were but also in the hopes the thing would run cool.

Still couldn't get it to stay cool and it was circulating coolant through the radiator properly. Took the t-stat out and it runs at the temp expect, cold. So cold the heat won't work, etc. The t-stat checks out in boiling water just fine so my only guess now is a air pocket keeping it from opening. Apparently the trick is to have a 1/8" hole in the rim positioned at 12 o'clock to allow the air to bleed out.

If that works so well why don't they all come with that bleeder hole? geez. lol.

Thanks for the info. I'm planning on flushing ours this winter, so I will keep that in mind. My Nissan 240sx was a PITA to bleed as well.

Vincent Keene · **Posted:** Tue Nov 17, 2015 11:16 am

Have you ever heard of the Air Lift system? Lots of pros use them because waiting for a cooling system to burp can take a while and that wastes time. I bought one via Amazon and it works just as advertised. All you need in addition to the system is an air compressor.

YouTube video Link

Amazon Link

You can borrow mine if you'd like to come and get it.

Chad Culbertson · **Posted:** Tue Nov 17, 2015 12:20 pm

Vincent Keene wrote:

Have you ever heard of the Air Lift system? Lots of pros use them because waiting for a cooling system to burp can take a while and that wastes time. I bought one via Amazon and it works just as advertised. All you need in addition to the system is an air compressor.

YouTube video Link

Amazon Link

You can borrow mine if you'd like to come and get it.

I have heard of it, but my currently location I have no where to put a compressor or power currently either. I'm hoping I can buy a house once we sell ours out in Forsyth county and a couple years will be buying a place with space for me to work again. Priority is at least a 2 car garage or a shop, lol. This whole working outside on a gravel driveway sucks, but it was the best we could find on short notice in the Pittsboro area.

I'm pretty confident putting a bleeder hole in the thermostat will solve my problem. Going to give it a shot tonight and see what happens.

I appreciate the offer though, I guess I could pick myself up a little pancake compressor, it won't run air tools but would do well enough for tires and using stuff like that.

Roger McDaniels · **Posted:** Tue Nov 17, 2015 2:03 pm

This HF compressor has been good for us; it makes 150 PSI and I can carry it around with one hand:

http://www.harborfreight.com/6-gal-15-hp-150-psi-professional-air-compressor-62380.html

We keep it on the Duff bus so we have some air at the track if we need it, and I use it around the shop for stuff that I don't feel like pulling in to a bay.

They go on sale for $99 from time to time.

Richard Casto · **Posted:** Tue Nov 17, 2015 6:04 pm

If the thermo doesn't have a built in bleeder, I wonder if there is a bleeder screw on the head somewhere? Or maybe a sensor (water temp sensor) that can be used as a bleeder to burp it?

Richard

Chad Culbertson · **Posted:** Tue Nov 17, 2015 6:43 pm

Richard Casto wrote:

If the thermo doesn't have a built in bleeder, I wonder if there is a bleeder screw on the head somewhere? Or maybe a sensor (water temp sensor) that can be used as a bleeder to burp it?

Richard

Yeah, there is a method using the gauge sensor in the back corner of the head. My issue with it is that with the valve cover bolted down I can't get a wrench or socket on it because of the proximity of the valve cover.

I had actually done this before deciding to replace the radiator and assumed I got all the air out, but it's possible more air made it's way back into the head after I tighten the sensor back down.

I'm hoping a bleed hole in the thermostat will just make it a little less work and I don't think a 1/8" hole will have any negative effect on temperatures, plenty of people online mention doing that, or buying one with a jiggle pin.

Chad Culbertson · **Posted:** Wed Nov 18, 2015 1:13 pm

It's running well now and staying cool. I think a couple issue were working against me, and I learned from them for sure.

I think initially I did in fact have some trouble getting the air out of the system, and drilling the 1/8" hole in the t-stat helped with that. The other issue which I have yet to resolve is that the gauge in the cluster is reading high. I connected to the OBD port and checked the coolant temp there and it was steady around 197 which is perfect since I put in a 195 t-stat. I let it idle for probably 20+ minutes while I put air in the tires and the spare and it never got hot even with the hood closed.

So, my official diagnoses in why it died is likely a bad fan clutch, you could stop it with your hand no problem. It has an electric fan which should cut on once the ECU sees a certain temperature so I probably need to test that somehow, not quite sure how though. Just the electric fan might not be enough to keep it cool during summer heat idling in traffic though, so it likely still had a lot of overheats which lead to the cracked head. Or perhaps the head cracked for some unknown reason, the head gasket was perfect, so who knows.

Either way, hopefully it will provide me with plenty of miles of service now, I think I'm about 1200 bucks into it now, so still not too bad. It still needs a head liner and some other odds and ends fixed but engine wise it should be all set after an oil change.

Chris Halweg · **Posted:** Wed Nov 18, 2015 1:22 pm

Chad Culbertson wrote:

It's running well now and staying cool. I think a couple issue were working against me, and I learned from them for sure.

I think initially I did in fact have some trouble getting the air out of the system, and drilling the 1/8" hole in the t-stat helped with that. The other issue which I have yet to resolve is that the gauge in the cluster is reading high. I connected to the OBD port and checked the coolant temp there and it was steady around 197 which is perfect since I put in a 195 t-stat. I let it idle for probably 20+ minutes while I put air in the tires and the spare and it never got hot even with the hood closed.

So, my official diagnoses in why it died is likely a bad fan clutch, you could stop it with your hand no problem. It has an electric fan which should cut on once the ECU sees a certain temperature so I probably need to test that somehow, not quite sure how though. Just the electric fan might not be enough to keep it cool during summer heat idling in traffic though, so it likely still had a lot of overheats which lead to the cracked head. Or perhaps the head cracked for some unknown reason, the head gasket was perfect, so who knows.

Either way, hopefully it will provide me with plenty of miles of service now, I think I'm about 1200 bucks into it now, so still not too bad. It still needs a head liner and some other odds and ends fixed but engine wise it should be all set after an oil change.

The electric fan should come on when you turn on the air conditioning and run constantly.

Chris Halweg · **Posted:** Wed Nov 18, 2015 1:25 pm

Also, this guy is popular with the club for tint. He did my headliner for $300 out the door and I am very happy with it.

http://shadesoundandsecurity.com/

Chad Culbertson · **Posted:** Wed Nov 18, 2015 2:37 pm

Chris Halweg wrote:

Chad Culbertson wrote:

It's running well now and staying cool. I think a couple issue were working against me, and I learned from them for sure.

I think initially I did in fact have some trouble getting the air out of the system, and drilling the 1/8" hole in the t-stat helped with that. The other issue which I have yet to resolve is that the gauge in the cluster is reading high. I connected to the OBD port and checked the coolant temp there and it was steady around 197 which is perfect since I put in a 195 t-stat. I let it idle for probably 20+ minutes while I put air in the tires and the spare and it never got hot even with the hood closed.

So, my official diagnoses in why it died is likely a bad fan clutch, you could stop it with your hand no problem. It has an electric fan which should cut on once the ECU sees a certain temperature so I probably need to test that somehow, not quite sure how though. Just the electric fan might not be enough to keep it cool during summer heat idling in traffic though, so it likely still had a lot of overheats which lead to the cracked head. Or perhaps the head cracked for some unknown reason, the head gasket was perfect, so who knows.

Either way, hopefully it will provide me with plenty of miles of service now, I think I'm about 1200 bucks into it now, so still not too bad. It still needs a head liner and some other odds and ends fixed but engine wise it should be all set after an oil change.

The electric fan should come on when you turn on the air conditioning and run constantly.

Yeah, it does, it cuts off/on when the A/C compressor cycles, so the fan is fine.

Thanks for the reference on the headliner, for that price I might let somebody do it for me, I was going to try and tackle it myself. I have done one before in an 89 Cherokee, although my great uncle helped me back then, he did interiors in classic cars.

Chris Halweg · **Posted:** Wed Nov 18, 2015 11:37 pm

Chad Culbertson wrote:

Chris Halweg wrote:

Chad Culbertson wrote:

It's running well now and staying cool. I think a couple issue were working against me, and I learned from them for sure.

I think initially I did in fact have some trouble getting the air out of the system, and drilling the 1/8" hole in the t-stat helped with that. The other issue which I have yet to resolve is that the gauge in the cluster is reading high. I connected to the OBD port and checked the coolant temp there and it was steady around 197 which is perfect since I put in a 195 t-stat. I let it idle for probably 20+ minutes while I put air in the tires and the spare and it never got hot even with the hood closed.

So, my official diagnoses in why it died is likely a bad fan clutch, you could stop it with your hand no problem. It has an electric fan which should cut on once the ECU sees a certain temperature so I probably need to test that somehow, not quite sure how though. Just the electric fan might not be enough to keep it cool during summer heat idling in traffic though, so it likely still had a lot of overheats which lead to the cracked head. Or perhaps the head cracked for some unknown reason, the head gasket was perfect, so who knows.

Either way, hopefully it will provide me with plenty of miles of service now, I think I'm about 1200 bucks into it now, so still not too bad. It still needs a head liner and some other odds and ends fixed but engine wise it should be all set after an oil change.

The electric fan should come on when you turn on the air conditioning and run constantly.

Yeah, it does, it cuts off/on when the A/C compressor cycles, so the fan is fine.

Thanks for the reference on the headliner, for that price I might let somebody do it for me, I was going to try and tackle it myself. I have done one before in an 89 Cherokee, although my great uncle helped me back then, he did interiors in classic cars.

That's basically why I paid someone else to do it as well. By the time I bought the adhesive and the fabric, IIRC I was approaching $80-$100 is parts. The speaker pods in the back also looked a bit tricky to get done correctly.

THSCC Forums

Cracked Jeep 4.0 head

Who is online