88 Jeep Comanche cooling issues

Very possible the vanes have gone. It's also possible your radiator is clogged. Is there a lot of buildup in it?

Keep in mind coolant flow when cold will be slow. That's the job of the thermostat valve. Full flow will only happen when the engine is at operating temperature. Needless to say the system is under pressure at that point and removing the radiator cap to look will get you seriously burned.

Where are you watching the coolant flow? My 88 MJ has that @#$% closed system so I don't really see the flow at the bottle (which is under pressure with no cap on the radiator to watch - it's on the bottle).

Have you drained the system lately? If so, it's possible to get an air block in the hose between the reservoir and the thermostat housing. That will over heat it in a hurry. This happens on refill it the hose is higher than the bottom of the reservoir.

How about a/c? Mine started running warm in traffic this summer and it turned out to be a diode in the module that connects to the coil of the fan relay - it uses steering diodes to merge the radiator tank sensor and the a/c switch for the electric fan. Fifty cent 1n4000 diode will cure that one - or get two and replqce both just to be sure. Of course, the electric fan may only mask the problem as mine ran all summer in West Texas a year or so back with the electric fan unplugged...

Sounds like either a water pump or a stick> Cl> > So we had a really hot day here awhile ago, and I ended up

I'm watching the coolant flow as it comes into the bottle (taking off the cap). I can see it speed up when someone tweaks the throttle to 1.5K, and watch it slow down to a trickle when it gets to idle. That makes sense, because as I was trying to struggle home after overheating, the temp would stay down until I was standing still, and even then I could keep the temps kind of down if I kept the rpm's up higher than idle.

These issues have started since I replaced the thermostat. I THINK the thermostat is doing it's job, as it heats up, and then usually levels off just under halfway on the temp gauge, which sounds right.

I don't have A/C, so I don't know if that affects your input. :)

Clint

On an 88, the first suspect when overheating is a bad rad fan clutch. When this goes bad it overheats when revving slow.

To test this, heat up the engine fully and have someone shut it down while you watch the fan. A good clutch will stop the fan almost instantly when hot. If it keeps on spinning, you need a new fan clutch.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

No a/c, no electric fan . Without the a/c, it wouldn't kick in until it got very near the redline anyway.

That flow bothers me - it says that you are cycling copious quantities thru the bottle - and mine does almost nothing except on shutdown and shortly after starting. Acts almost the same as an ordinary overflow bottle in an open system. The only time I see that kind of flow is when I have just re-filled the system and it is purging the rest of the air out as it heats up and pulling the fluid out the bottom to replace the air. Normally, on shutdown it will fill a little then get drawn down as the engine runs on rerstart. I'd guess that something is plugged - radiator, collapsed intake hose, etc.

Mike's suggesti> I'm watching the coolant flow as it comes into the bottle (taking off the

Huh. I figured it should be circulating on a regular basis.

Thanks for your input, both you and Mike. I took it into the shop for an estimate; it's a small town, and they've been gentle with me in the past. :) I'll post back in here when I find out what it is. The guy who owns the shop did 20 years at a Jeep dealer in the nearby big city, and he indicated a common failure was the radiator itself.

In the meantime, I'll just lube up my wallet...

Clint

If the fluid is flowing unhindered in and out of the bottle (if you can watch circulation) makes it sounds that the radiator cap is bad.

A lot of places now recommend new thermostats and caps at each coolant change (especially when DexCool is used) because the failure rate is increasing tremendously.

Mine has no flow to speak of.

The old closed systems were prone to have the tank crack and/or the cap not fit well which will cause coolant to flow into the bottle just before it escapes onto the ground.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

Good point, Mike. You have to remember that the cap on the tank IS the radiator cap and that the tank is under the same pressure as the rest of the system. I keep waiting for my radiator to go so that I can replace the whole system with a "normal" system using an overflow bottle and a real radiator cap.

Ever notice that the part you would like to replace seems to last forever?

The diagnosis from the garage is a new water pump and new bottle/cap. They are recommending replacing the thermostat as well, at the same time. The thermostat and bottle/cap are no-brainers in terms of how-to (I think; I've done the thermostat before), but does anyone have a cheap source in Canada for the bottle? They're quoting $100 for the bottle, and $15 for the cap, which seems ridiculous, although the local NAPA says they can't get them for any price, so rarity is probably inflating the price. Something I can get in a timely fashion to Edmonton Alberta, in particular.

The water pump I'm not so sure about, but my neighbor has offered to assist in the operation. I've got the full-service manual as well, but that might not be the final answer either. Ah, well, the library has a Chilton's and Hayne's guide, I think. :)

Clint

I believe you either need a bottle 'or' a cap and not a pump unless it is leaking out the bottom of the snout under the pulley.

If the bottle is cracked and you have to buy one, then you may as well get a new cap. More likely the cap washer is just old.....

If this only happened once in hot traffic, then I would almost suspect the old cap just wasn't tight enough.

You can do a visual inspection yourself. If your bottle has a long time seep or crack, there will be a green stain by the crack. If the cap washer is bad, there will be green stains around the rim. If it was a one time thing because the cap was loose, it should be clean. If it actually overheated because you have a bad pump or t-stat, then the top of the cap will have stains.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

No, it's happened before. The bottle is cracked, as well, apparently. The bottle was my first choice in replacing; I just figured something else was wrong too, as I doubted the low flow would have been caused by a slightly leaking bottle.

And I suspected the water pump was leaking as well (drips under vehicle overnight), so I'm not entirely surprised by that.

Any suggestions for Jeep parts up here in Canada? I phoned a couple of local places and got a couple prices on the water pump, and they weren't too ugly. At least I'm a little more informed about what I'm getting into, anyway. And I found at least one US source on eBay for the tank (around $30), but it looks like they'll only ship UPS, which sucks up here to Canada. The one parts place I talked to suggested a wrecker, but with the issues I've heard with the tanks, it's not something that I really want to replace 3 or 4 times trying to get one that's not cracked or anything.

I did find this link on the Net, WRT replacing the pump, if anyone else is interested:

pretty straightforward on there, with the possible exception of the 4th bolt holding things in place. Of course, I'm expecting my mileage to differ. I'll have to weigh the labour charges the garage gives vs. the money I can make doing some contract work... Clint

You may be able to glue the bottle, depending on the size and location of the crack.

Earle

overheating

Make sure you get the correct pump. Somewhere along the line they changed to a reversed impeller. I understand it is quite common for the reversed and non reversed pumps to be in the wrong box at the parts house. They are easy to tell apart as the reversed models will have an 'R', "REV', or 'REVERSE' stamped into the impeller.

Be sure to replace the thermostat and cap while you are in there, they fail at the most inopportune times. Get the correct thermostat.

Replace the factory springs clamps, they are a bad design to begin with and cannot be retensioned. Stainless steel screw clamps are cheap.

While you are doing all this you should probably flush the cooling system, adding a flush-n-fill kit makes this child's play.

Finally, be sure to use the proper coolant.

Mike Romain can give you pointers for Canadian suppliers, generally speaking you can get any Jeep part you need at Canadian Tire, The Beer Store, or Tim Horton's.

In many smaller Canadian towns that is all in one building.

I've had nothing but grief with Canadian Tire, and their local parts department. I replaced my thermostat about a year ago, and I was in and out of there at least 3 times trying to get the right part before I finally yanked out the old one, took it in to them, and found out they didn't have a matching one. Went down to the NAPA store, and was out of there in 5 minutes with the right one.

If nothing else, I've got selection. The local garage is a decent place in a small town, so if he starts screwing people around, word will get out quickly, I'm sure. Then the Canadian Tire is about 15 minutes away, with the NAPA and a Parts Source (haven't checked them out yet) about 17 minutes away. There's supposed to be a wrecker about 20 minutes down the road from me, but I haven't ventured down there yet.

While I'm doing all this work, you're probably right that doing a flush would be a reasonable idea. My only concern would be breaking loose a bunch of crud that was nicely settled into place. :) No idea if that's a valid concern or not, though.

Thanks for the input, guys.

Clint

I bought one a couple of months back from a local junkyard - they had a whole bin of them - for about $30 and that included the cap. I got the same story at the dealer you did - ouch! Until I found this place, I was ready to make my own out of sheet copper with a regular radiator cap and a sight glass I had laying around but I don't recommend this unles you've done a bit of sheet work.

Before you try mending the bottle, remember that it IS under pressure same as the radiator. Assuming 15 psi, it is really hard to get a decent repair in that polyethelene bottle and that still leaves the cap to fit. The last bottle I replaced had problems around the neck on top and would not seal with a new cap.

That crack would account for most all the overheating - same as a bad radiator cap.

Have you tried the mail order houses for a bottle? I've seen them somewhere - surely sombody has a few sitt> The diagnosis from the garage is a new water pump and new bottle/cap. They

I found a whack of them on eBay for $27 US ($30 Canadian), but nothing in Canada. If anyone is aware of any mail order Jeep places in Canada, I'm all ears (and eyes, I guess).

Clint

The cracked bottle lowers the pressure in the system. This will radically change the temperature at which the coolant starts to boil, so hot boiling spots can appear inside the head which raises the level of the coolant in the bottle to the point of overflowing out the crack or blowing the seal on the cap from too much pressure now caused due to the boil.

The 'flow' you see in the bottle is caused by this boiling over. It is 'not' normal to see much flow in that bottle. The bottle isn't part of the circulation path of the fluid, it just takes up the expansion of the fluid that happens every time the engine heats up.

Just FYI, when I replace waterpumps I don't mess with the fan belt unless I plan on changing it. Getting the PS pump loose and unadjusted is a pain in the butt. Tightening the belt back up correctly is a worse pain in the butt.....

The pump will unbolt and pull out with the fan belt in place. Then when the new pump goes in, the belt goes back on exactly the same as it was before.

Try Canadian Tire or NAPA for the pump. Their parts last as long as the $tealership's parts it would seem.

Mike

Cl>

So I phoned around to a few of stealerships this weekend, and found one that had the bottle and cap in stock. $100 in parts ($88 for the bottle, $12 for the cap), 15 minutes in labour, and my Jeep seems back in business. Ran around town a bit on Saturday, then to and from work again today.

On thing I did notice was more fluctuation in the temp gauge that seems "normal". It would slowly go between 1/4 to 1/2; never getting over 1/2. Is that a sign of anything bad?

In any case, thought I'd post back here, and let the people in the thread know the scoop. Thanks for all your help.

Clint