Suspect water pump
 

Just a brief run down for anyone that doesnt know, been having an ongoing overheating issue that I've been trying to trace down. I've replaced the thermostat, radiator and ect sensor and tried bleeding air from the system several times (no air in system fyi). The only components left that could be a cause are a leaky head gasket (ruled this out as no bubbles in coolant when up to temp), or the water pump. Anybody have sny input on how to go about testing the water pump on our cars or is there not really a way to test it? Thanks in advance and look forward to the responses :)

This is a video with the thermostat open in case anyone needs visuals

When you bled the system, were you able to get full heat coming out of the vents? I assume you did but did you install thermostat in correct position so it opens properly? Also very important, do your radiator fans come on when coolant gets hot?

Also, a bad water pump usually is accompanied with a noise

Yes i do get hot air out of the vents and also made sure to orient the thermostat the same as i took the old one out. The only other symptom i get is that when the car is warming up as it gets to the point of opening the thermostat i will get a slight dip or hesitation in the rpm's

Can't tell in that video if you have coolant flow or not. Next time suck some coolant out so that it's below the filler neck. So that you can see movement. I've only seen 2 water pumps that wouldn't flow. Both were over 200,000 miles with impellers that was numbs. Nothing left of them. Both on V8 Chevys. 3 ways a water pump goes bad. The seal starts leaking. You can see the drops out of the weep hole. No noise most of the time. The bearing goes bad. You'll hear the noise. Or the impeller wears out. No noise or leaking. Just slowly stops flowing coolant over a long period of time.

If head gasket. Most shops can add a chemical in the coolant to help sniff for combustion gases.

Just because there aren't any bubbles in the coolant doesn't mean you have a head gasket issue. You need to get a block tester so you can better diagnose if you have a head gasket issue. I just had a car a few weeks ago that had blown head gaskets and when we took the car for a road test and monitored the Engine Coolant Temperature, the temp would barely get above 210. Once, we got back to the shop and took the cap off the degas bottle there was an extreme amount of pressure in the cooling system.

Are you sure that your fans aren't intermittently not working?

I don't think its your water pump, our water pumps have metal fins pushing coolant through the engine. But hey, don't rule out broken water pump fins even though I've never seen someone said that they had it happen to them. Here at Ford, like on the 3.5, the fins are plastic and will come apart sometimes at about 100K then the car will over heat. Another way too check if it could be your water pump is witness marks coming from the weep hole or mlky oil. This is due to the pump leaking and going into our oil since our water pumps are under the front timing cover like on the Ford 3.5 gasser. This can set VCT codes. Get a cooling system pressure tester and pump it up to the pressure on the cap and watch for leaks at the weep hole, etc.

A whining sound isn't always accompanied with a bad pompe de agua.

No it isn't, but usually when the bearing goes it'll make noise. And it's more like a gurgle not whining. I never said always btw

https://www.amazon.com/gp/aw/d/B0007...sYL&ref=plSrch

We have used this stuff at my shop to detect leaking head gaskets. Does the car always overheats? Does it overheats during highway speeds? Or in traffic/idling only?

This is the stuff I was thinking about. Just had a case of CRS! :shakes head:

I did do a block test with a block testing kit, fluid didnt change color. Also the only time it starts to overheat is at idle with the ac on, otherwise it seems to be able to keep normal temps. One other symptom i noticed is that when it gets to higher temps i get a little bit of tapping that seems to switch between the 5th and 6th cylinder, when i rev the engine the tapping stops, it stays quiet for a little bit after i let off but then returns shortly almost like coolant is not flowing enough through those cylinders to keep them within their temperature spec

Also fans are working like normal as always, just an addendum to everything...when the old radiator was swapped out it had a pretty extreme amount of scaling around the upper radiator inlet so the cooling system was definitely neglected before i bought the car

Sounds like it may have been run without antifreeze.

You may have some of the same scaling on the pump impeller fins and/or water passages, reducing pump output and flow through the system.

That was my thinking right there too, i ran a bottle of the prestone super flush cleaner through the system for a few days before i swapped out the radiator and did get a pretty good chunk of white powdery stuff that ended up inthe overflow reservoir if that tells you anything

I know lol.

What do you work on at your shop? A little bit of everything?

This. Sounds like it's also due to poor maintenance by the previous owner like the OP stated.

That chunk may have been part of the impeller. I'd plan on replacing the pump and doing a very close inspection of the entire cooling system. If the corrosion is bad enough to eat the impeller, no telling what other damage has been done and what has been plugged up.

The whole reason i swapped out the radiator was that i was having the exact problem im having now with the system only overheating at idle with the ac on. You think running some more cleaner through the system would help or should i plan on replacing the water pump and then run cleaner through it afterward?

I don't think using harsh chemicals is the answer. I would consider it, at best, a temporary band-aid that may do more damage than good. But you may not have much choice at this point. YMMV

I'd do an inspection of the block (you may be able to use one of the cheap borescopes/endoscopes that you can find online nowadays) for corrosion before going too far.

I do have a borescope so i guess I'll have to get that in there, one thing to note though....this whole saga started a couple of months after i had the dealer do a coolant flush. The coolant that was in there beforehand i have no idea how long it was in there but it was still green in color. Before that i had no problems for the close to a year i had the car before i had them flush the system.

IMO a coolant flush, tranny flush are the worse 2 things you can do to a car. I've hardly ever heard a good thing about them It's mostly always been a horror story. Your's is just another one on the list of reasons why not to do it. The bottom half of your radiator could be plugged from the scaling that got knocked loose/dissolved from the chemicals they used for the flush.

If your issue is only at idle you need to look at the radiator fans. Make sure they are kicking up to high speed at idle and they are both working. You could test these with Nissans Consult. Not sure how you would do it without the Consult tool. Uprev or Ecutek may be able to do it.

I am going to ask a silly question. Did you remove the bleed screw out of the radiator when filling with antifreeze?

:iagree:

Chemical flushes worked when engines were made of iron but anything strong enough to eat the corrosion is strong enough to eat aluminum.

Very likely. And any other small passages.

Definitely worth checking before taking more drastic measures.

A non-contact tachometer will tell how fast the fans are spinning (may be able to borrow one at a parts store). Not sure how fast they are supposed to turn but that info may be in FSM. Or compare to another Z.

Have checked this multiple times and both kick on high speed when the coolant temp hits about 214

Flush was done before i swapped out the radiator and rest of system was filled and drained multiple times with distilled water to clear the system of the cleaner. Only thing that i didnt do is backflush the system with the thermostat off

Sounds like you are done and need to take it to someone with more knowledge than you. Just sayin.

Took it to a shop, they are the ones that suggested to swap the radiator and if that didnt work they suggested to do the water pump next

They should be able to check the radiator before deciding whether or not to replace. Same with the pump.

If the radiator is plugged with sludge, the block probably has some sludge buildup too.

I'm still not 100% sure that corrosion/sludge is the problem (although it sounds like the top candidate). If it were me, I'd inspect the radiator and pump before I started replacing parts. I'd do whichever was easiest first. You should be able to get a good idea of radiator condition by pulling the inlet hose and using your borescope.

Radiator is an almost brand new unit though that i swapped in

Until you do some investigating, who knows what the real problems is? Check for corrosion and sludge before you start swapping parts.

If corrosion is not the problem, check for flow. FSM may have a procedure.

I'd also double-check fan speed. I doubt that they are the problem but one may not be getting up to speed.

Will do, thank you sir! :)

I started turning wrenches 5 years ago at one manufacturer(lexus) so I can only base my experience from that. I came from oil changes, diagnosis to engine overhauls. Generic diagnosis might be similar but part design, type of noises, common issues, procedures, etc could be way different so sometimes trying to fix one car based on another doesn't always work. Fortunately switched to Porsche two months ago so no longer with boring lexus :driving:

Anyhow lets try to help OP to fix his car. Since the car is only overheating on idle with ac on I cant really think of anything except insufficient air flow through the radiator. If there was an air pocket it would still overheat with AC off, the heat in the cabin would fall off from hot to warm during idle. Strange..

It has been very strange for me as well, I've been going through the most common points of failure in the system starting with the thermostat and working through the most common procedures to address the issue. The only thing that i havent changed in the system is the water pump which is partly what leads me to believe it may be the culprit by process of elimination. I appreciate the help in this situation and look forward to any more input anyone has on the issue :)

Yeah, it sounds like a fan issue while the OP is at an idle, even though the OP has said the fans are working.

its not just the fans are working though, I can feel with my hand a pretty good amount of air being blown through the engine compartment when they are on and also feel a good bit of air being sucked through the front air dam when I put my hand in front of it. also, as someone suggested I went and rented a radiator pressure tester. pumped it up to 16 psi and it holds pressure steady with no indication of any leaks, let it sit there for a good 5 minutes too with no drop in psi at all.

The two basic problems that I've run into with air/liquid heat exchangers both have to do with flow - either the air or the liquid is moving too slow (too fast is also a possibility, but not very common and certainly not your problem).

You seem to have good air flow (although your testing methods are not very reliable). Low flow is usually caused by a bad pump or blockage (stuck 'stat, something in a passage, heat exchanger pluggage, etc).

You've checked all the easy stuff. Go ahead and pull the pump for inspection. Use your borescope on the block while you have things apart.

Before you drive yourself crazy and start taking the car apart, I suggest you get a proper coolant funnel kit (link below). What Im about to suggest is not possible without one because coolant would spill everywhere. So fill the coolant to 1/3 full of the funnel, start the car and turn on the heater all the way to max temp and max fan speed. Also make sure to adjust vents to face mode only and make sure AC is off! Run the car and give it several good revs to like 4-5k and hold for 5-10sec. Back off and repeat. This way you build extra pressure to push coolant around and possibly eliminate any air pockets that still might've been trapped in the system. Make sure you keep watching funnel through your windshield to make sure coolant is not excessively raising. If it does, back off for little and try again. Keep doing until fan kicks on and off couple of times. From experience some cars will bleed just fine from idling, others need that extra push especially when cooling system was completely opened. Hope it helps

https://www.amazon.com/Lisle-24610-S...ice+kit+funnel

I realize my hand is not a very reliable way of testing, but it's what I have access to lol. I don't have access to the tool to set the crankshaft in place to loosen the crankshaft pulley so looks like I will be saving up for a little bit before I can have the shop inspect the water pump for me. gonna drain the system this weekend in the interim and take a look around with my borescope and try to get pictures for those interested.