1998 Volvo S70 How to check water pump without pulling?

[precopster]

Given that you have done all the above I'm still convinced you can "boil" this (snigger) down to two components:

1) Coolant temp sensor
2) Water pump

Even if temp sensor reports 105deg C at fan activation it doesn't mean the sensor is in calibration.

[charleskennedy23]

How do you know it's overheating? If you are going by temp guage then it could be temp sensor. If there are other signs or you are using an external thermometer to get the temp then it's something else. My temp sensor went out and the gauges were reporting overheating but the car was behaving as it should. Temp sensor is an easy fix and only runs about $50 from ipd.

[cn90]

At 250K miles+, I'd advise you to replace the Water Pump.

The Aisin WP has a lifespan of about 180K-200K. After that, it either:
- starts leaking a little bit
- or the impeller falls off, search for photos by "rspi".

As mentioned, use only Aisin WP (HEPU is OK too but Aisin is better).
Make sure you clean the block nicely (blade to scrape off old gasket, then use steel wool to clean it really well). I wrote a TB, SB, WP DIY in forum a while back.

PS: Photos of broken impeller in the thread below:

http://volvoforums.com/forum/volvo-s70- ... ing-75223/

[erikv11]

Of course the relevant point would be the miles on the water pump ... and the pumps don't automatically fail at 180k-200k or any other mileage. Just pointing out the obvious that cn90 didn't already cover in his post, which has good info.

To answer the question OP posed in the title: you can certainly tell if the pump is not working at all, by feeling the radiator hoses in the engine bay. Once the temp gauge gets up to 3 o'clock, feel the top hose, it should get very hot from the coolant flowing through it now that the t-stat is open. Does the lower hose get hot or stay cool? Similarly, does the heater get nice and hot, pretty quickly (although the heater test is not as good)?

All that said, I agree with the others: it's either the pump or the ECT, and if the pump is original or of unknown mileage then it would be wise replace it.

[roscoerich]

To answer if I knew it was overheating by the temp gage alone, yes- it was boiling over and have been through a few expansion caps already. Replacing the ECT today, but yes looking back on the records of the car for the last 14 years, I think the water pump is the original and just hoping the ECT will get me through a couple of months before tackling the job.
Question! I was told that I could run the car without the T-Stat to see if water was flowing through the radiator hoses, but at the same time I was manually pumping the hoses and yes it became very hot. Is running the engine without the T-stat a bad idea? or should I put it back in before next test with the new ECT? By the way, I'm in Texas, so it's typically pretty freaking hot this time of year, but it's a beautiful cool rainy day today...

[erikv11]

When running without the stat the engine will have a tendency to run a little cool, so in general it is indeed fine for troubleshooting purposes. Don't manually pump the hoses at all; does the pump send scorching hot water and heat up the hoses all on its own? Does the heater get super hot just as quickly as the engine does?

Once you confirm the pump is working and move on to testing the ECT, I would install the stat. Keep in mind, the whole theory about the ECT being the problem is that it is not telling the fan to turn on when it should, so there is no air cooling, so it overheats. For example, with a bad ECT the car would probably not overheat on the highway, especially if it was being run without a stat. Whatever you do, be super careful to not overheat and warp the head, it can happen from just one trip of the needle into the red.

If the ECT is indeed the problem then your strategy to wait on the pump is fine. Plenty of people use a 3-timing-belt interval on their factory water pumps (225k).

[erikv11]

... The cooling fan is working. ...

OK I missed this one. If the fan is working, and the pump seems to be pumping through the rad, and the heater core is heating up, it's probably not the ECT but change it anyway, because they do get old and fail and the water pump is a lot more hassle. A partially broken water pump impeller or some other blockage is about the only thing left to explain the symptoms.

[roscoerich]

Thank you guys for your help. I will post later today if the hoses heat up on their own after replacing ECT. I have been very cautious about letting it get into the red. The heater seems to start working quickly after starting the car, so does that mean the heater core is getting heated from the engine alone or because there is still some life left in the pump?

[roscoerich]

Oh and the fan is working great at idle for 10-15 minutes plus, but when I get it on the road is when it's boiling over. Could that perhaps be the ECT not functioning in drive properly? As I said replacing it today. How long would you guys recommend leaving running at idle before I get on the road again?

[erikv11]

The heater also gets its hot water from the water pump, so getting heat quickly is consistent with the pump working. Your idea about the ECT is a decent one but I don't know. The ECT can actually be tested by putting it at various temperatures and checking the resistance, but you're so close to replacing it I would probably just go that rote. Make sure the connectors to it are clean, too.

Boiling over only when it gets on the road would also be consistent with a weak water pump (partially broken impeller) or a clogged cooling system, they would show similar behavior.

I would warm it up by driving around the block a couple times then watch it idle in the driveway for 5 minutes, if it seems OK then try a longer drive, something like that.