Heat isn't hot - Water pump problem?

A few months ago, I converted my '89 XJ to the later "open" cooling system. I installed a new radiator, new thermostat, new heater control valve, and new hoses. Now that it's cold, my heat isn't working as well as it should be. I've even gone so far as to thin out the coolant/water ratio(60/40), and block off part of the radiator, and it still comes out of the vents at barely lukewarm temperature. I don't recall if the heat was working properly before the swap, as I didn't drive it much between the time I bought it and last summer.

That said, the gauge rarely gets to the halfway mark. I think the electric fan may come on too soon. Also, if I park the truck and bring it up to about 2500rpm, the heat works great. This leads me to believe that the water pump isn't pushing hard enough to get hot cooling flowing all the way to the heater core when I'm cruising. Am I crazy? All of the other parts of the cooling system are new.

Also - and I'm not sure that this is at all related - Every once in a while, the truck will leak coolant, but only when it's not running. It appears to be coming from the water pump area(above the front crank pulley down the driver's side of the block), and I assume it's coming from the weep hole in the pump. Could this be due to a faulty radiator cap that may not be relieving enough pressure? I don't know what PSI they're supposed to be rated at, but the new one that I installed during the swap says 16psi on it.

Help me guys, I'm freezing to death!

You have a hot water valve which is vacuum actuated. just check the lines leading to the firewall to the heater core, make sure that they are warm after the valve, unplug the vacuum line and try to manually operate it, sometimes if you get a vacuum leak somewhere there may not be enough vacuum to keep the valve open. When you rev it up you have more vacuum. it also may be just air in the system or low coolant. few things to check anyways, good luck.

my waterpump lasted about 2 months after the it began leaking when I shut it off, be prepared, when it goes man it goes!

maalox said:

Also - and I'm not sure that this is at all related - Every once in a while, the truck will leak coolant, but only when it's not running. It appears to be coming from the water pump area(above the front crank pulley down the driver's side of the block), and I assume it's coming from the weep hole in the pump. Could this be due to a faulty radiator cap that may not be relieving enough pressure? I don't know what PSI they're supposed to be rated at, but the new one that I installed during the swap says 16psi on it.

Help me guys, I'm freezing to death!

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mine does th exact same thing. i come out in the morning and there is a large puddle of coolant underneath. i see it running down the lower rad. hose. also only happens at temps under 35 degrees outside

Does your engine maintain a decent operating temperature? If so, your water pump is working fine.

When was the last time your heater core was flushed? It doesn't take much surface buildup to seriously degrade heat transfer.

The vacuum-powered heater control valve (near the firewall) - how old is it? They do sometimes stick - it could be stuck partially open, and when you spin the water pump faster, you get more coolant going through the heater core (and less "stagnant flow" in the core.)

For the leak, did you replace your water pump when you converted? The weep hole isn't there for pressure relief - that's what the cap is supposed to do. The weep hole is there so you can see that the shaft seals are failing - which they probably are. Not necessarily pressure related - you've got a fast-spinning shaft spinning against a rubber seal, so it's going to wear out.

Also, check for a leak at the water pump end of the lower radiator hose - it can sometimes present as a leak from the weep hole (even going so far as to spray up there and drip from the water pump housing.) You'll see whitish deposits everywhere that coolant has evapourated - which is usually how I find pinhole leaks. If it's too confusing (there are too many deposits,) they're usually loose - a Nylon brush, like an old toothbrush, should break them loose. Run about for an after-noon, and check again.

Before I replaced my leaky radiator I had a similar issue...

Basically while the vehicle was sitting there idling it wouldn't put out any heat at all, but once you got going it would be just fine.

Turns out I had lost so much coolant that day, that my heater core was starved for coolant, however I doubt that's the problem in this case.

It's very important that you fix any leaks in you cooling system, they just get worse the longer you leave them, and then one day somethings going to give.

5-90 said:

Does your engine maintain a decent operating temperature? If so, your water pump is working fine.

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Yeah, it's consistently just below the halfway mark on the gauge. Minor fluctuations, but always between 1/4 and 1/2 after it's warmed up. I have never seen it go past 1/2.

When was the last time your heater core was flushed? It doesn't take much surface buildup to seriously degrade heat transfer.

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I have never done it, and I highly doubt the PO did, either. Should I flush it in both directions, or do I risk screwing it up that way?

The vacuum-powered heater control valve (near the firewall) - how old is it? They do sometimes stick - it could be stuck partially open, and when you spin the water pump faster, you get more coolant going through the heater core (and less "stagnant flow" in the core.)

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You know, I checked that thing out pretty good. With the truck running at idle, moving the hot<->cold lever inside the truck moves the lever on the heater control valve accordingly. I figure that if there's a vacuum problem with it, it would be most apparent at idle.

For the leak, did you replace your water pump when you converted? The weep hole isn't there for pressure relief - that's what the cap is supposed to do. The weep hole is there so you can see that the shaft seals are failing - which they probably are. Not necessarily pressure related - you've got a fast-spinning shaft spinning against a rubber seal, so it's going to wear out.

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That was the one major component that I did not replace. It looks like I'm going to be though. I read here on about a high-flow water pump (Hesco? IIRC), but I'm not sure that triple the price of a standard water pump is worth it. Thoughts?

Also, check for a leak at the water pump end of the lower radiator hose - it can sometimes present as a leak from the weep hole (even going so far as to spray up there and drip from the water pump housing.) You'll see whitish deposits everywhere that coolant has evapourated - which is usually how I find pinhole leaks. If it's too confusing (there are too many deposits,) they're usually loose - a Nylon brush, like an old toothbrush, should break them loose. Run about for an after-noon, and check again.

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Well, when it leaks, it LEAKS. It left a couple of nice puddles under the truck for about 2 days, then I topped it off, bled the system, and it hasn't leaked since. The lower radiator hose wasn't replaced when I did the swap, as it looked OK at the time. When I was under the truck looking for the leak, it looked a little bulged near the water pump, but nothing that I would normally be concerned with.

The other thing I had considered was that perhaps the blend door in the heater box was stuck/messed up/etc, but I have no idea how to check that. In my experience working with other cars(older VWs mostly), the only way to get the HVAC to recirculate air was to put it on Max A/C or turn it off completely, and(correct me if I'm worng here) it appears that is the case with these trucks, too. Personally I feel that this is a design flaw, but I guess we have to work within the parameters we're given by whoever designed the thing.:looney:

UPDATE:

Today I flushed the heater core(which had more crap in it than I expected), installed new heater hoses, and removed the vacuum-operated heater control valve. The heat is SCORCHING. I had to turn it down because it was almost too freakin' hot. Also worth noting is the A/C still seems to cool the truck off just fine(though it is ~25 degrees out, so I take that for what it is at the moment). I'll be keeping the control valve just in case, but I don't think I'm going to be needing it again.

A few temperature observations:

@ idle(~1000rpm in my truck...f'n RENIX):

*Temperature gauge is just below the 210 mark
*Upper radiator hose 155-165
*Upper heater hose 175-185
*Lower heater hose 170-180
*Thermostat flange 210
*Radiator cap flange 145
*Heat coming out of the vents 155-165

@ 1800rpm, no load

*Temperature gauge is just above the 210 mark
*Upper radiator hose 165-175
*Upper heater hose 185-195
*Lower heater hose 165-185
*Thermostat flange 210
*Radiator cap flange 130
*Heat coming out of the vents 175-180

While driving, the temp gauge drops between the 1/4 and 1/2 mark, and stays there. As it goes, I'm pretty satisfied with the results. It cost me about $15 to do(coolant, 6 ft of 5/8 heater hose, and 4 new clamps), and about 30 minutes of my time. Not too shabby.

On a side note - whomever created the stupid spring-type hose clamps should be dragged behind the nearest building and flogged repeatedly.:twak:

maalox said:

:

On a side note - whomever created the stupid spring-type hose clamps should be dragged behind the nearest building and flogged repeatedly.:twak:

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Ahahaha, you just need the proper pliers and they're a breeze.

Get rid of those and get regular hose clamps that you tighten with a screwdriver/socket/wrench!

Cant you just delete that heater valve?

JNickel101 said:

Get rid of those and get regular hose clamps that you tighten with a screwdriver/socket/wrench!

Cant you just delete that heater valve?

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"... and removed the vacuum-operated heater control valve." As I read that, he did.

I know it can be done safely - because I've done it as well. Also, I think it was deleted by ChryCo later on anyhow...

Oops my bad, I skipped that part....or something...

dlarrivee said:

Ahahaha, you just need the proper pliers and they're a breeze.

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Heh...I've got them. I've even got the nicer set with the cable on them for getting clamps in tight spots. I still hate them. The design is inhenertly poor, as they lose some of their tension every time they are squeezed, so over time, they lose the ability to clamp properly, causing a leak.

5-90 said:

"... and removed the vacuum-operated heater control valve." As I read that, he did.

I know it can be done safely - because I've done it as well. Also, I think it was deleted by ChryCo later on anyhow...

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Yeah, that's exactly what I did. As an update for how it's working after sitting overnight to cool off - It's much better than before. It warms up faster, I have heat within 5 minutes of leaving the house in 25 degree weather, and the temp gauge gets up to 210 and stays there(or slightly below).

maalox said:

Heh...I've got them. I've even got the nicer set with the cable on them for getting clamps in tight spots. I still hate them. The design is inhenertly poor, as they lose some of their tension every time they are squeezed, so over time, they lose the ability to clamp properly, causing a leak.

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They're not meant to be re-used.

My 2001 XJ doesn't seem to have one of these heater valves btw.

Yeah, I think they got rid of them when they went to the "open" cooling system...

5-90 said:

"... and removed the vacuum-operated heater control valve." As I read that, he did.

I know it can be done safely - because I've done it as well. Also, I think it was deleted by ChryCo later on anyhow...

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It's not really an issue of saftey. By having it in there the A/C doesn't have to work as hard. Later systems were designed without having a heater valve but not the earlier ones. The valve closes off coolant flow in the coldest temp position and I think in Max A/C. Without this valve the A/C has to overcome heat generated by having hot coolant heating up the heater core in the HVAC housing all the time even with direct airflow through the heater core blocked by the temp door. If you don't use A/C then it won't matter but if you want it to work better in the coldest setting then leave it in.

dlarrivee said:

They're not meant to be re-used.

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Right, so from a serviciblity standpoint, they are completely useless. I stand by my original point that the designer of such a useless device should be flogged.

5-90 said:

"... and removed the vacuum-operated heater control valve." As I read that, he did.

I know it can be done safely - because I've done it as well. Also, I think it was deleted by ChryCo later on anyhow...

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hey i was just wondering where in line that heater valve is? under the hood on the way into the firewall? or under the dash near the heater core?

is it pretty easy to delete that valve cause i am having same heating issues as these other guys. what parts does it take to do this cause i think i will try it. its -5 here at night and i'm freezing!

philagony94xj said:

hey i was just wondering where in line that heater valve is? under the hood on the way into the firewall? or under the dash near the heater core?

is it pretty easy to delete that valve cause i am having same heating issues as these other guys. what parts does it take to do this cause i think i will try it. its -5 here at night and i'm freezing!

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Near the heater core connections at the firewall. You could probably use heater hoses from a 97-up. Flush out the heater core while you are at it (back/forth with a hose on both line connections).

excellent! i will try that next week when i do the brakes on the heep jeep! thanks MJR