Newbie with a couple questions

[ClemXP]

Hi Everyone!

 

I just purchased an '87 4x4 manual 4.0 litre with 141k miles last week. It was well maintained by the first 2 owners, and has very little rust (even under the floorboards) so I'm really pleased so far!

 

I have a couple questions regarding the 4WD, CAD and cooling system.

 

1) My 4WD light stays on all the time, except when I am getting into the higher RPM's in 3rd, 4th or 5th gear (climbing a hill on the interstate, for example) Ive read that the 4WD works on vacuum, any ideas what might be the problem?

 

2) I am interested in locking my CAD, looks simple enough and I'm pretty mechanically inclined. Any reason not to do it? Should it just be done? Will doing that keep my 4WD light on all the time (and maybe a previous owner already did it? I haven't checked)

 

3) Lastly, the last owner had overheating problems. He had the head gasket replaced and new thermostat recently. The top coolant hose is hot when the engine is, so I'm not worried about it. However, when I drive up hills (4WD) or on long mountain roads, I notice my coolant bubbling and spraying out of the vent cap when I pull over. Any suggestions on how to prevent future issues? Will swapping for the radiator with the overflow bottle automatically fix this, or is there anything else I can do?

 

4) one more thing - any recommendations on aftermarket tachs or temp gauges that I can install? I like knowing these things ;)

 

Thanks everybody! This looks like a great community to be a part of.

BTW, I live in California (truck is originally from near Reno, NV) near Tahoe in the summer and in SoCal in winters.

:cheers:

[MJRemi]

I just wanted to say WELCOME to the Club. I'm not one of the experts so I can't answer your questions but check again later for the know-how guys responses. We love pictures so break out the camera. :cheers:

[kastein]

Hi Everyone!

 

I just purchased an '87 4x4 manual 4.0 litre with 141k miles last week. It was well maintained by the first 2 owners, and has very little rust (even under the floorboards) so I'm really pleased so far!

 

I have a couple questions regarding the 4WD, CAD and cooling system.

 

1) My 4WD light stays on all the time, except when I am getting into the higher RPM's in 3rd, 4th or 5th gear (climbing a hill on the interstate, for example) Ive read that the 4WD works on vacuum, any ideas what might be the problem?

 

2) I am interested in locking my CAD, looks simple enough and I'm pretty mechanically inclined. Any reason not to do it? Should it just be done? Will doing that keep my 4WD light on all the time (and maybe a previous owner already did it? I haven't checked)

 

3) Lastly, the last owner had overheating problems. He had the head gasket replaced and new thermostat recently. The top coolant hose is hot when the engine is, so I'm not worried about it. However, when I drive up hills (4WD) or on long mountain roads, I notice my coolant bubbling and spraying out of the vent cap when I pull over. Any suggestions on how to prevent future issues? Will swapping for the radiator with the overflow bottle automatically fix this, or is there anything else I can do?

 

4) one more thing - any recommendations on aftermarket tachs or temp gauges that I can install? I like knowing these things ;)

 

Thanks everybody! This looks like a great community to be a part of.

BTW, I live in California (truck is originally from near Reno, NV) near Tahoe in the summer and in SoCal in winters.

:cheers:

Not sure on 1), 2) yeah go for it (it was eliminated in later years, just block off the vacuum lines etc), 3) is your radiator plugged or corroded badly maybe? could be time for a replacement. 4) don't bother with aftermarket! Go to your nearest junkyard and pull the gauge cluster from any 87-90 4.0L XJ or MJ that has the full gauges, along with the oil pressure sender and temperature sender at the rear driver side of the head right next to the valve cover bolts. Set the odo to match yours (it's easy on a 90 or earlier) take a digicam pic for legal proof and stick all the new parts in yours, and you are done!

 

You can use an 87-90 2.5L gauge cluster as well, but you'll have to adjust the tach to be accurate since it basically counts pulses from the ignition control module, on a 4cyl there are only 4 pulses per rev while the 6cyl has 6 per rev so obviously it'll be way off without being adjusted. Not sure about if you can use the cluster from a diesel XJ/MJ but if you find one, let us know, a bunch of guys on here would LOVE to buy parts out of one.

[Sir_Brando]

Hi Everyone!

 

3) Lastly, the last owner had overheating problems. He had the head gasket replaced and new thermostat recently. The top coolant hose is hot when the engine is, so I'm not worried about it. However, when I drive up hills (4WD) or on long mountain roads, I notice my coolant bubbling and spraying out of the vent cap when I pull over. Any suggestions on how to prevent future issues? Will swapping for the radiator with the overflow bottle automatically fix this, or is there anything else I can do?

 

 

First thing I would do is just a simple flush. Flush kits are pretty cheap and 90% of the time it fixes that exact problem. Flushed my 97 GC Laredo with the same symptoms and ran like a champ afterwards. Also pulled a bar of soap sized chunk of stop leak out of the lower hose that the PO left for me. Welcome to the club!

[ClemXP]

Well the radiator is brand new, too, so that can't be it. I'm most concerned about the 4WD light, any thoughts, anybody?

 

Here she is:

 

[Wildman]

To answer your #1 question.........

 

There is a vacuum switch under the pressure bottle (which we'll discuss in a minute) on the right hand inner fender that controls the 4wd light, in most cases, the switch is shot, and is available for about $100, or do what most of us do........pull the wire off the switch and the light will go off and stay off. When you put it in 4wd HI you should be able to tell when it's in 4wd, same with 4wd LOW. You can feel the "pull" from the front axle. Only do this on loose stones/dirt/snow, never drive a NP231 on hard dry pavement, you'll tear the transfer case right out of the rig :eek:

 

If you have a new radiator, and a shop did the work, the only real problem with an '87 4.0, well all Renix era ('87 - '90) is the "closed" cooling system. If the air is not "burped" out of the system it will overheat. But you say that the coolant is spraying out of the vent cap, that could be your problem, that vent cap is really a pressure bottle, that's part of the "closed" cooling system, and the best solution is to replace the pressure bottle, it is not an "over flow" bottle, it is pressurized from the cooling system, there are some after market pressure bottles, that I'll let others post up, but a replacement pressure bottle is readily available on e-bay for about $22.

 

To lock the CAD, there are several articles on this channel about that........Like HERE

 

The "quick" fix for getting full gauges is from a donor XJ from the Renix era ('87-'90) it's all plug and play with what you have now, but as noted above, try to get a gauge set from a 4.0 and save your self some trouble. viewtopic.php?f=2&t=4615

[Geonovast]

on a 4cyl there are only 4 pulses per rev while the 6cyl has 6 per rev so obviously it'll be way off without being adjusted.

 

Just to be nitpicky :smart: and to clarify, a 4 cylinder has 2 pulses per revolution, a 6 cylinder has 3. Still would obviously need to adjust a 4 cylinder tach to be correct on a 6.

 

:thumbsup: