Cj5 Is It My Water Pump?

Hi guys!

I have a 72 CJ5 with a V8 that sat for 6 years and I got it running again earlier this year.

The last time I took it out it seemed like it was hotter than usual. (My temp gauge isn't working)
Anyway, I took off the radiator cap and let it run for awhile and get up to temp to see if the water was circulating in the radiator. It wasn't. Just sat there. I replaced the thermostat and flushed the radiator when I got it running. It seemed fine for the first few months. I think this is a new development.

Even though I had just replaced it, I took it out and tested it in boiling water. It opened up. So now I'm not sure what else to do. Is there a way to check the water pump? It isn't leaking or anything. But something is keeping the water from circulating.

Is there anything else I should do or anything else I should check? I appreciate any help you can offer.

 

I would think you need to confirm the engine block and radiator temperatures under normal operation.

Are you sure it is getting warm enough to require the thermostat to open? Or, conversely, is it overheating?

A hand-held remote infra-red thermometer is cheap and very useful.

 

I have one of those laser temp guns that you shoot at things and it tells you the temp. The morning after it seemed hot to me I drove it around town and stopped every once in a while and shot it at the block, radiator, the upper hose and the lower hose...I don't know why I decided to do that really. Just to make sure it wasn't getting super hot I think. I cant remember what the temps were but I know the lower hose was about 30 degrees less than the upper one. What temp should the block, radiator, etc. be at? And should I get a thermostat that opens sooner? Mine says 195 on it.

 

In my experience, it's usually the radiator that's the problem with an old car. I would try a good chemical flush of the system before I condemned the radiator. Unfortunately today you can't readily get the quit effective cooling system flush chemicals that you could years ago, due to laws against dumping caustic chemicals.

These Jeeps came with optional fan shrouds (heavy duty cooling) which are available aftermarket and will improve cooling efficiency some.

 

Not convinced yet that there is any problem.

Use your laser thermometer. When the top of the block reaches 195º-plus, you should start seeing a warm radiator. The lower hose should be cooler than the top, if the radiator is functioning.

But no part of the entire system should ever get beyond a few degrees above boiling point (212ºF).

 

Run it with no t-stat, see if water is moving. Or better yet, knock the center out of an old t-stat and run with that. If water flows then pump is working. Then put a good t-stat back in it.

But if pump is old consider replacing, or have it rebuilt. Note that AMV V8 original pump housings are getting rare and import castings on new are not so good sometimes. So dont throw away pump if its an AMC casting.

 

Oh! Well that's good to know. I'm pretty sure that it's the original water pump. I hope it's not the pump though. I looked at the instructions and taking off the fan and all that other stuff doesn't seem fun to me. The worst part is that nothing has been apart. Probably ever. So breaking things loose can be something of a challenge. I've got the flush stuff in it now. But the no thermostat thing is a good idea. I'll do that next. I'll keep an eye on the temp of everything with the laser. Thank you so much.

 

Hello Candace,
Good advice above.

 

Ok. I did the flush and filled it back up and when it was running with the radiator cap off, after a bit, the coolant kinda started to raise, like it was going to want to splurt out of the top. So I put the cap back on. Is that what it's supposed to do? Does that mean pump is working?

 

Yes.
IMO, It's not your water pump. Try to get your temp gauge working , to see what the real engine temp is. Most likely some plugged cores in the radiator.
Maybe you got it by flushing ?

 

So how hot was the block when that happened? Was the radiator warm or not??

 

Hi Candace - A water pump that just stops working would be a really unusual failure. They are very simple mechanically - just a paddle wheel in a housing, turned by the fan belt, that pulls water in one opening and pushes it out the other. Typical failure instead would be wearing out of the bearings which subsequently ruins the seals on the shaft. The bearings get loose, the seal leaks and coolant comes out a weep hole on the pump. If you get down there and look closely at the pump, you'll see the hole. When coolant comes out there, time is short before complete failure.

In mechanical work, measuring is important, maybe as important as understanding what you are doing. The first thing I would do is fix the temperature gauge. Electrical work can be daunting, but I believe the TSM has a step-by-step procedure for repair of gauges. Do you have the TSM for your year? ROckAuto has it on CD-ROm for about $20 More Information for DETROIT IRON DCDC104 or you can buy a paper copy for considerably more 1972 Jeep Factory Service Manual We can help you, if needed.

You can also get one of those infrared thermometers mentioned above at Amazon or wherever Amazon.com: Etekcity Lasergrip 774 Non-contact Digital Laser Infrared Thermometer Temperature Gun -58℉~ 716℉ (-50℃ ~ 380℃), Yellow and Black: Kitchen & Dining - I have this one, works great.

Don't guess, measure. Measure, measure, measure!!!

 

If pump works then both upper and lower hoses will be hot after thermostat opens. I've read of impellers coming off the shaft but thats really rare.

With belts off the pump pulley jerk the pulley around and if there is any slop then its about to start leaking. Somehow I had a pump with sloppy bearings that hadnt started leaking, but it wont take long.

Another thing worth knowing. The timing cover forms the back half of water pump housing. A not-ruined timing cover is precious. Maintain your coolant so it doesnt corrode the cover. Don't let a pump get loose and eat into your cover. Their weak point is oil pump wear, so if yours makes oil pressure you have a good one.

IMO an intermediate deserves an AMC V8 if it came with one. Even if not an original 304.

 

Well...last night after I finished flushing the radiator and I filled it with coolant like I said. So then I decided to take it for a ride and see what happened.
It did fine the five or so miles into town and to get gas. Those are all pretty flat roads. Then I started to take it up the hill. The road is about a mile and a half and climbs 400 or 500 feet. It is a paved state highway. Speed was around 45-50mph. When I got most the way up I could feel a light mist of water on me. Pulled over. That weep hole you mentioned was pouring coolant. Temp was around 210 I added water and coasted as far as possible to home. Engine was running I just tried not to use it much. Got home and the water was pouring from the pump. It hadn't leaked a bit before that. Not out of hole or anything. But I had just felt like it wasn't right. And now I guess I know. So I need to replace the water pump for sure, right?

 

As Chilly mentioned, grab a fan blade and try to wobble it. If the bearings in the pump are failing, the water pump shaft will wobble in the housing.

Now, this is the weep hole on the water pump itself, not the radiator overflow hose coming from the radiator. If water comes out of the weep hole, you must replace the water pump. Not a hard job, and Jeeps give you a lot of room to work. You thinking of doing it yourself?



JMO (just my opinion) - the pump leaking is not going to cause overheating. That's a separate problem. But you need to replace the pump before you drive anywhere.

Take a look here - Jeep® 1974 TSM online The water pump replacement procedure is in chapter 2. Two things to realize here - The '74 TSM here will not match your Jeep exactly. The cooling system is the same, so that aspect of it will be useful, but not everything is the same. Second, these books were written for the dealership mechanics to refer to when they worked on the new cars. The book won't tell you what they expect the mechanics to already know.

 

True. But be cautious not to snap any bolts that might be seized up.

 

My radiator overflow is the hose that comes off the top of radiator and goes into the little bottle, right? That's not anywhere near the water pump, which I think is under all the pulleys on the front of the motor. But it wasn't the radiator thing for sure. When I first thought the Jeep seemed hot, the water pump wasn't leaking. It didn't start to leak until after I flushed it and drove it up the hill. Then it was leaking out of that weep hole at the top of hill and gushing out from all around the pump when I got home.

So, yes. I was planning on doing it myself. I have an online repair manual I have been referencing and I appreciate the link timgr gave me. Its nice to have a couple of places to go to for instruction. Sometimes when one doesn't make sense the other one will.

It seems like kind of a lot of stuff to take off to get to it, but at least there is a lot of room in front of the engine to work.

 

RockAuto shows a GMB pump for your Jeep. More Information for GMB 1102908 The Wagoneer guys like the aluminum GMB pump, but it's only for '73 and newer.

Suggest you get friendly with your local olde tyme parts store and have them order in this part for you. Or get the part that they recommend, but be very picky about the new pump being exactly the same as the old. Put the new and old pump side by side on the bench and compare. Make sure the pulley fits without rubbing. Make sure the impeller turns without rubbing, when the gasket thickness is included.

 

I recommend anti seize on reassembly of the water pump.
If it has a fan clutch I'd inspect it.

 

Pro tip: carefully track where each bolt comes from. The 1/4-20 are only two lengths but the big bolts are more varied.