Signs of water pump failure? (long) (1 Viewer)

[John E Davies]

I have been chasing a summer steep-grade overheating issue with my '96 LX450 since I got the truck 2 years ago. What I have done:

rebuilt head
new cap and radiator (3 row metal from Radiator Barn)
new thermostat and hoses
new fan clutch
new fan shroud
new plugs and wires
flushed, tuned, and tweaked the engine
NO leaks in the cooling system
Stock ignition timing
green coolant, changed yearly
Tried a "water wetter" from NAPA (with no improvement)

The truck has Slee bumpers/ sliders and 275/85 tires with stock gearing. I tow a small 600 pound trailer.

Here's what is happening - maybe someone can help me figure this out, PLEASE!

On looong steep mountain grades the engine temp climbs slightly as the truck slows from 70 mph, then the temp stabilizes at 60-65 mph in 3rd gear, no OD. As the grade worsens and I drop to 2nd at 60 mph the temp starts to climb fairly rapidly and the a/c shuts off. If I slow down to 50 or so the temp will stabilize, but the a/c will not come back until well into the downgrade. If I stay at 60 or 65 in 2nd the temp will continue to climb.

I am confused! I thought that going to a lower gear does two things - it gives a smaller throttle opening (less load on the engine) and higher revs (more water flow), both of which SHOULD give better cooling. On my truck the temp spikes when I downshift.

Is this a sign the water pump is failing? It's about the only thing I haven't replaced. I have never heard of this sort of "soft" failure - I thought they either worked fine, or squealed or leaked....

Can anyone shed some light on this? What does your truck's coolant temp do when slowing on a steep grade? Thanks very much for any insights or suggestions.

BTW this only happens at temps over about 80 deg F and is independent of altitude. It will do it at 1500 ft or 7500 ft. It seems to be rpm related more than anything.

John

 

[landtank]

If you are running WOT, I don't think the RPM increase from running a lower gear will help you as you're creating more heat as well as circulating more coolant.

How long are these grades that you are pulling? I just got back from vacation and tugged my 3500 lb camping trailer in 90 deg weather up some steep enough grades to haev the truck down shift into 2nd with no over heating at all.

I just replaced my radiator before this trip and couldn't find a single aftermarket one that I would consider over the more expensive OEM. How would you rate that Barn one?

 

[IdahoDoug]

John,

Since you're basing this all on a temp issue, what are you using for measuring the temp? I'm assuming the factory gauge and mention this in the context of some reporting inaccuracies - no reason yours couldn't be overly sensitive vs others finding UNDER sensitive.

I also wonder about the rad you bought, and have over the many years I've been associated with the 80 heard very poor results from aftermarket rads - even some expensive "racing" ones.

As to the water pump, I agree with you. Have never seen what you aptly called a "soft" failure, so I would not put this at the top of the list. I also agree that the higher RPMs is the cooler strategy vs any hint of lugging (lower RPMs/same load). Read a very involved towing study once and uniformely the higher rpm strategy was best. Anectodally, the trannies were producing an incredible amount of heat by comparison at the lower rpms.

Rereading your post, you don't actually seem to have any overheat symptoms save the A/C cutting out and seeming to not re-engage quickly. If the temp is coming down but the A/C is remaining on vacation I wonder if the thermal switch is too quick to cut out A/C and reluctant to engage it??

DougM

PS - I have two factory 93 copper/brass radiators lying about that work fine for cooling and both weep from the seam but could figure into a problem solving for you if you need one for a while. Just say the word if you want to throw one in and go floor it up Mt. Spokane....

 

[dd113]

It sounds like a flow problem to me but the symptoms dont really add up. I would have replaced the WP when the head work was done or with the new rad. I have seen WPs work at less than 100% and the symptoms often mimic a fan clutch going out. Is the fan clutch OEM? The WP is the one link in the system that is not new; I would replace it just cuz.

You might also triple check the timing and the water hoses around the throttle body. EIther/both might be wierd after the head work.

 

[MTNRAT]

Ditch the aftermarket rad.
Cheers,
Sean

 

[Rusty Phillips]

different thought

arent the 3rd and OD lockup, whereas the 1st and 2nd gears do not lock up

thus when you go into 2nd, the transmission is using the torque convertor instead of the lockup and is heating all that trans. fluid (and sending all that trans fluid to the tranny cooler, heating up the air passing thru the engine radiator, causing your temp gauge to go up)

so while your higher rpms do spin the fan faster, the tranny is putting out a lot more heat


maybe the best thing is to stay in 3rd (1:1) and let the speed drop

 

[John E Davies]

Thanks for the replies....

I am reluctant to go with the oem radiator for cost and durability reasons - there have been reports of exploding plastic tanks, and also they are almost completely impossible to repair in a dinky backwater town. The one I used looked to be equal in size and seems well built, so far.

I am basing all my observations on the factory temp gauge. The engine never pukes coolant or boils over, but a fuel injected engine really won't show ANY other signs of overheating, so it's hard to tell. When I pop the hood at the top of the grade at a rest stop, it is definitely hot as hell in there!

Maybe my trailer is contributing to the problem - I run only 18 psi in the 31 inch tires since they are so lightly loaded. I am sure the rolling resistance is high, but I want the flotation of the wide tires for soft surfaces and I like the squishy ride to protect my camping gear. They don't get hot on the highway, so I am sure they aren't under-inflated.

The fan clutch is oem, and it does roar at startup.

As far as letting the tranny stay in 3rd - that is simply not an option, or the speed would degrade so far the tranny will kick into 2nd by itself. I do tend to run in as high a gear as I can, depending on the grade, and I VERY rarely run WOT

I think at this point I will recheck the ignition timing and plan on replacing the water pump the next time I change the coolant. I am done with epic summer trips ths year.

IdahoDoug: Do those 93 metal rads fit the 96? If a new pump doesn't do the trick I might try one, but it will be next year before I know for sure.

Any other advice will be appreciated.

Thanks, John

 

[landtank]

I personally think replacing the water pump is a waste of time. The vanes would have to be broken off or worn down quite a bit to influence flow wouldn't it.

It's not the physical size of the radiator but the density of the passenges that will determine how well it will cool. When you drain an fill the system do you know how much coolant you use? I noticed that my new 93/94 radiator took about a gallon more coolant than the original 96.

last note": how does your AC condensor look? If that thing is real dirty (clogged), not much air is getting through to the radiator.

 

[dd113]

I personally think replacing the water pump is a waste of time. The vanes would have to be broken off or worn down quite a bit to influence flow wouldn't it.

It's not the physical size of the radiator but the density of the passenges that will determine how well it will cool. When you drain an fill the system do you know how much coolant you use? I noticed that my new 93/94 radiator took about a gallon more coolant than the original 96.

last note": how does your AC condensor look? If that thing is real dirty (clogged), not much air is getting through to the radiator.

Good point on the condenser but the WP could easily be bad and just as normal PM should be replaced. I have seen a few with the bearing wallowed out in the race and the shaft wobbles a bit but not enough to really see. This prevents full flow.


And yeah, always use OEM rads!

 

[landtank]

Good point on the condenser but the WP could easily be bad and just as normal PM should be replaced. I have seen a few with the bearing wallowed out in the race and the shaft wobbles a bit but not enough to really see. This prevents full flow.


And yeah, always use OEM rads!

The last time I've replaced a WP was back in 78 I think. I had always thought that once the bearing was worn it would leak, basically needing replacement. I don't see me replacing mine until I see a leak.

 

[santiagol]

I had similar WP worries but solved my persistent overheating problem by installing an aftermarket electrical fan and now the truck never overheats and even the A/C is happy in grades and traffic jams. I even think it runs better. So I guess I will wait until the WP leaks to change it.

 

[John E Davies]

I had similar WP worries but solved my persistent overheating problem by installing an aftermarket electrical fan and now the truck never overheats and even the A/C is happy in grades and traffic jams. I even think it runs better. So I guess I will wait until the WP leaks to change it.

Can you tell me what fan you used? Was it in addition to the stock fan (a pusher in front of the radiator) or a complete replacement?

If a complete replacement, I am a little surprised at your results, because the typical electric fan does not flow anywhere near as much air as a fully locked mechanical fan. The biggest Perma-Cool twin fan does flow a healthy 5900 cfm, (and it is NOT recommended for towing). And it is $529 (!!!) at Summit Racing.... They show a model for a 2000-2002 V8 Tundra - I wonder if it would fit an LX450?

http://www.perma-cool.com/Catalog/Cat_page18-1.html

Thanks.

John

 

[santiagol]

I installed an auxiliary pusher fan in front of the A/C condenser. It is actually mounted on the condenser, I made four brackets to grab the upper and lower condenser frame since I prefer not to use the standard thru-the-radiator nylon gizmos.

The fan is identical to the 14-inch flex-a-lite syclone model http://www.flex-a-lite.com/auto/html/syclone.html. It was about $85 plus I purchased the thermostat control and a Bosch relay. When the thermostat control switches the relay on, the relay delivers 12 volts directly from the battery to the fan. You can also wire it to start with the A/C or control it with a switch.

The additional airflow really made a difference, the A/C is happy and the truck never overheats. I set the variable thermostat control to start the fan just when my supposedly accurate temp gauge moves a tad over the middle of its range. Unlike before, it stays there even in noontime traffic at 95 degrees.

This was an inexpensive fix - one of those projects that give you really noticable results under budget. If you have a Lexus with the original A/C condenser I think CDan has a unit that bolts directly to the brackets.

 

[Tools R Us]

I use a 14" also, more on fan installs here;

https://forum.ih8mud.com/showthread.php?t=51171&page=2&pp=30

 

[John E Davies]

Thanks for the help. I am reluctant to go with that 14 inch Flex-A-Lite Syclone, in spite of it's quiet design - it draws 9.2 amps for 1505 cfm. The PermaCool Turbo Flex draws 9.5 amps but pulls 2950 cfm.

Since there is a 20% loss for pusher installation I think I will go with more flow. I don't really need the fan for stop and go traffic, so noise isn't a real issue for me. I think I will just wire it with a relay and on/ off switch for full manual control.

John

 

[Dusty]

original post says 65 mph in 2nd gear w a 600lb trailer in tow on a hot day. If your rig has kicked down to 2nd gear and and you are pushing her to 65 mph, what rpm are you turning? How long are you running the pass with this combination? how loaded is your rig? what type of grade?
Is it possible that your rig is in good shape but you may just be asking too much of the mare?

 

[IdahoDoug]

John,

Yes, the 93/94 brass and copper radiator is a direct bolt in. That was one of the first PM items I did when I got my 97 this spring. It's proving to be just as bulletproof in the cooling department as the 93 is. Meaning either truck can go for several minutes at a time at WOT on 90-95 degree days pulling 6000lb over passes at 20-25mph. I mean that too, full WOT mashed on the carpet. Believe me, I know that's extreme duty. After reading all the various bandaids being done for 80 cooling systems over the years, I'm more and more convinced that people who bought used 80s have radiators clogged to varying degrees and that the way to solve this correctly is a new OEM rad. I prefer the 93/94 but have no data.

DougM

 

[97 FZJ80]

John,

Yes, the 93/94 brass and copper radiator is a direct bolt in. That was one of the first PM items I did when I got my 97 this spring. It's proving to be just as bulletproof in the cooling department as the 93 is. Meaning either truck can go for several minutes at a time at WOT on 90-95 degree days pulling 6000lb over passes at 20-25mph. I mean that too, full WOT mashed on the carpet. Believe me, I know that's extreme duty. After reading all the various bandaids being done for 80 cooling systems over the years, I'm more and more convinced that people who bought used 80s have radiators clogged to varying degrees and that the way to solve this correctly is a new OEM rad. I prefer the 93/94 but have no data.

DougM

Does the OEM 93/94 radiators have plastic tanks?

 

[landtank]

Yup

 

[powderpig]

Nothing wrong with the plastic tanks either. The may not last as long if they are not taken care of, but if they are they can last as long as 13-15 years (I have one on the 93 that is 13 years old and If I had not broken the over flow nipple it would be a long time before I needed replaceing).
Some thing is just not right with your engine, As dougs states and I have had similar experence with heavy loads and working my trucks real hard. Never have I had this type of over heating issue, even with more heat from Higher HP engines. What kind of oil are you running? How many miles on your truck. Who did your head gasket (I do not remember if you done your own)? And on top of the pass when you look at your engine, you see no bubbles in your overflow tank?? With the engine running at 3k or more. Any how sorry to see you are haveing problems, It could be the metal rad as well, most that I have seen have been not that great in quality. Off to read to the kid, later robbie