1999 V70 NA cooling issue [Broken Water pump Impeller]

patsusedparts · Post by **patsusedparts** » 18 Mar 2021, 06:07

I have a 99 Base model V70 (Denso). I have had it for over 9 years. Currently has 222,000 miles. When I got it in 2012 (170,000 miles) I took off the head and sent it out for a valve job. Also, of course, timing belt, tensioner, water pump, head gasket. The car has suddenly developed a serious overheating/cooling issue. In all the years I've had it the temp gauge has never gone up off cold until I was driving. At idle, the needle would be at or near the bottom. Once you are driving it, it would come up to just about the middle and stay there. This past weekend suddenly changed and now it will go up to the upper mid range at idle, a bit higher than it used to be under load. And if you drive it around the block it climbs into the red and starts to boil out of the reservoir. Cooling fans are coming on, as I think they always had been. And the ECT sensor seems fine. I measured less than 300 ohms at about 220 degrees and as it cooled the resistance went up. I've been performing some other diagnostics. So I'll summarize what I think is of use, but feel free to ask about anything that I may have missed.

When starting cold I measured the temp with a laser thermometer at the thermostat housing, as well as where the upper hose enters the rad and also where the lower hose exits out of the rad. Tracking those three as it was warming. The thermostat outlet cover got to over 220 F. But the upper hose and entry at the top of the rad were only about 100 F. and the outlet at the bottom of the radiator was only 84 F. So I replaced the thermostat, thinking it may be stuck closed. It made no difference. So I figured I had better check to see if the head gasket was blown, so I did a dry and then wet compression check. Although the rings are worn in 3 of the cyl, in the wet tests everything was over 150 psi. most over 180. Also the engine is running fine and the oil on the dipstick is not milky at all, so I think I can rule out the head gasket. Finally, I ran it with the cover off the reservoir as a triple check for the head gasket. As it idled, no bubbles, no gurgling so I left it run for a few minutes with that open. For a few minutes, nothing much was happening to the level in the tank until (in a matter of seconds) the level rose up smoothly but steadily rising and began to overflow in a pretty solid continuous flow. I am guessing that was at the time the thermostat started to open, but I ran to shut it off quickly and didn't think to point the temp gun at it until later.

So here are my current thoughts. It seems to me that there is next to no flow going through my radiator. And that is likely my issue. I have not flushed it ever, so it certainly could be so clogged up that nothing can get through, but I would have expected that it would clog gradually and I would have noticed something changing. But this issue seems to have occurred overnight. Full disclosure, it happens that I have hardly been driving the car in the last few months. And I don't know if that might cause clogging to happen more rapidly? Or maybe I just didn't notice??

The only other plausible cause I can imagine is that the impeller has started spinning on the shaft inside the water pump. That theory "feels" good with the fact that the car was perfectly normal one day and then essentially unusable the next, but the way the water flowed out the open reservoir really looks like it was being pushed by something more than expansion. Plus, this seems like a rather unusual failure. And of course, I'd really like to think that either flushing or replacing the radiator is the fix, because that is so much easier than doing the water pump.

I welcome any suggestions or diagnostic ideas you have. If there is a reliable way to confirm if the radiator is clogged or not, I'd like to know it.

Thanks in advance.

Post by **abscate** » 18 Mar 2021, 06:37

It does sound like a clogged radiator, have you been changing coolant every 2 years/30,000 miles?

If the water pump at 170k was AISIN or Volvo, I would not worry about it. I dont think anyone here other than Jimmy has seen a spun impeller on a VOlvo water pump.

You have to use an OEM thermostat and ECT on these cars or chase a lot of monkey tails.

IF the thermostat passes the boiling water on stove test, I would dump the coolant, and run a hose through the top of the radiator and see what the flow is like,

patsusedparts · Post by **patsusedparts** » 18 Mar 2021, 08:32

Thanks abscate. I have not changed/flushed in the past 9 years/50K miles

Like often happens, sounds like I was part of the problem by letting it go way too long.
I'll run the hose in the top hose this weekend and probably find it flowing back out in my face.

I replaced the thermostat yesterday, the old one was fine. And I think I can rule out the ECT sensor, since I measured the resistance and the fan responds as it should.

Post by **abscate** » 18 Mar 2021, 09:06

Oooof.

Well, you saved about $150 in coolant and another 100-150 in time, so you will probably still be ahead after a radiator change...and kudos to catching it before anything major.

It is carrying 'run to fail' mantra to the extreme, though.

Let us know how the rad looks.

patsusedparts · Post by **patsusedparts** » 19 Mar 2021, 18:51

Well the saga continues. I didn't have much time tonight so I ran the car at idle until the gauge was up in the middle. As mentioned in the first post, the gauge never came up much at all at idle, until this week. Once it was hot I turned the heat in the car on; full temp and highest fan. Nothing but cold air was coming out of the heater. After a couple minutes I shut it down and I checked the 2 heater hoses where they enter the firewall and both were around 74F. So I can't rule out the water pump with that result. In the morning I may remove the thermostat and run it for a couple minutes to see if the temp takes any longer to get to the middle of the gauge. I may even run it for a second with the upper hose disconnected to see how hard it's pumping.

Also, since no matter what it is, I am so overdue for the radiator flush; I'll do that as well and see how clogged up it is.

Post by **abscate** » 20 Mar 2021, 03:26

You have quick connection the heater hose , too, first grab the necks up at the firewall and give them a nice twist until the brass is rotating in the oring, maybe a 1/8 turn or so.

Now you can squeeze the yellow clips with needle nose and gently work the copper part out. Nice and slow here so you don’t break the plastic bulkhead connector. Pull straight and rotate a bit back and forth, and it will come out slowly and ( don’t call me ) Surely.

Some 5/8 Tygon clear tubing will let you evaluate flow without spilling , or you can use heater hose to a container

Here’s you flow diagram fir the Chem Engineer 101; you could have a plugged radiator and / or plugged heater core.

patsusedparts · Post by **patsusedparts** » 20 Mar 2021, 08:06

Thanks for the testing method. And thanks for all the support here, as always.

I didn't see the most recent post until after I did my own look this morning. I drained the system and the AF came out clean and green. Then I poured clean water in the top of the rad and it came pouring out just as fast and clean as I could pour it in. The current timing belt has 52,000 miles on it. So I'm just going to buy the whole timing kit and leave the radiator alone for now.

I have brand new heater hoses I bought a couple years ago, but never installed. Which actually reminded me that I kinda DID flush the cooling system. I did the heater core replacement a couple years ago (not fun), I had completely forgotten about it. Probably why the AF and rad are clean.

I didn't really need another project, as I am in the middle of this:

.. but whatever!

So I will order the parts but I likely will not do any work for a week or two. When I get back to it, I will post an update of what I actually found once the old water pump is in my hands. Seems to me that it must be the pump.

Azik09 · Post by **Azik09** » 22 Mar 2021, 01:44

Check the thin hose from thermostat (or radiatot, location may vary) to coolant tank and both nipples it fitted to for being clogged. I often drill nipple on thermostat to 3 mm to prevent clogging. Looks like you have a big air bulb in coolant system.

The only other plausible cause I can imagine is that the impeller has started spinning on the shaft inside the water pump.

I met this issue sometimes, but only if water pump was replased by cheap one or "noname" manufacturer.
You have a cold air from heater, so I think radiator is not guilty. Even if it is completely clogged, coolant should circulate through small circuit, including heater core.

patsusedparts · Post by **patsusedparts** » 26 Mar 2021, 17:18

As Adam Savage would say : "There's your problem right there!"
Yep, water pump.

Thanks for all the support

befarrer · Post by **befarrer** » 26 Mar 2021, 17:50

Is that an Aisin pump? Post some pics of the other side and its markings. Is the impeller plastic or metal?