Need help diagnosing cooling issue
 

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.:eek: 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. 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. :D

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.

What brand of water pump did you use? I've never seen a factory brand pump impeller have a problem. But I imagine an aftermarket pump could fail that way.

Trying turning the heat on full blast, to see if it still overheats - if so you may a water circulation problem. I trust your cooling ran works at the correct time, and should run if the ac pressures are high enough.

The WP was "probably" Gates. But it was 9 years ago, so I really don't know for sure. The electric fan seems to run appropriately for the conditions I can actually measure. When I first switch on the AC it doesn't start immediately, but it will after a minute or so. And when the car is hot and the fan is running, it will run-on for 3-5 minutes with the engine off. Seems to be functioning as it always has, but of course, I don't much pay attention to it unless something is wrong.

I will definitely test to see how much the heater core can cool it down this evening.

Thanks hoonk

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.

Radiator is not clogged at all, in fact the coolant was looking clean. I flushed with clear water and it was flowing out as fast as I could pour it in. Since the timing belt has 52,000 mi on it, I am just going to get the entire timing kit and do the job.

I'll post what I find once I get the old pump off the car, but that almost has to be the problem.

Fixed
 

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


https://cimg2.ibsrv.net/gimg/volvofo...73d4ab370f.jpg
https://cimg3.ibsrv.net/gimg/volvofo...eb3a23ee21.jpg


Thanks everyone I appreciate the support.

I don't think I would use that brand of pump again -

Well I'll be darned. Thanks for posting that. I've never seen such a thing.

Solved - failed WP impeller
 

So I wanted to wrap this up. I fixed the car, so all is well on that front. :) A few people have inquired about the old pump. I am attaching a photo of the only marking on it. I actually did not purchase or install that pump in 2012. The car's previous owner (friend of mine) brought it to a shop for service. They said it had jumped time and the belt etc needed to be replaced. The owner approved the work. The next day the shop called and said we replaced the timing belt but now it won't start at all, so you must have bent valves from the jumped timing. At that point the guy said NO to the $3300 the shop wanted to fix it, and he sold it to me. Short story, the shop had the timing well off. So I pulled the head, (nothing was bent) and had the valve job done and put it all back. And I drove it for 9 years with the parts that shop had installed.

So back to the pump, the only brand I see is "Altrom". Which I am not familiar with (obviously, I'll remember it NOW!!) :eek:

https://cimg7.ibsrv.net/gimg/volvofo...09da5a153b.jpg