1998 v70 overheating, coolant circulation problem

[Ben850]

Anyone any updates?
I'm having the same issue... My heater core blew, I replaced it.
Now it overheats again, fan comes on at 102 Celsius but the coolant temp rises regardless. Radiator lower hose as well as the upper hose are cold...

It is the time of year.

See recent thread.

https://www.matthewsvolvosite.com/forums ... 0&start=14

[grntrdbx]

Ben, I don't mean to hijack your post, but maybe we can help each other out on this one.

I'm having/have had the same issue with my '99'V70XC. I had taken it into a shop to address the issue a couple of years ago and they couldn't figure it out.....so it has been a driveway fixture for the past 3 yrs. It runs good but it overheats. It seems that I'm having the same issues as you. I say issues because my '04' V70R is currently in the shop and I felt the time was right to revisit the '99' since it is begging to get back on the road.

I haven't found a coolant flow path diagram on the site or on the web yet, so if anyone has one, could you please post it? This would really be helpful in troubleshooting this issue.

Ben, did the car run hot or overheat before you replaced the heater core? I'm thinking that if it ran hot or got close to overheating before the heater core blew you may have debris in the coolant system now. Have you or anyone (a repair shop) flushed the radiator or the coolant system yet? I was thinking back when I took my XC in to have them look at the same issue and I can't remember if they flushed the coolant system. I drained the system and (as I remember) back flushed the radiator and the radiator was flowing good. I can't remember if I ran water through the engine to see if it flowed from the upper hose to the lower engine output where the lower radiator hose is connected (with the engine off). I remember doing this in the past, but that may have been a couple of years before the original issue when I had replaced the radiator. I think I replaced the heater core a year prior to the radiator change too. I think I also replaced the overflow tank and radiator to overflow tank along with the cap (green factory one) around the same time.

I'm not sure if this helps, but I think I'm going to start the diagnosis from scratch again and try to get the '99' back on the road.

This is what I've done so far (I actually started tonight):

I pulled the old thermostat and bought a new one. I cleaned the old one and tested them in boiling water on the stove to see if and when they both opened and closed, and they were both within a couple of degrees of each other. Check thermostat off the list.
I then installed the new thermostat and topped off the coolant in the overflow tank and ran the car with the overflow cap off for about 10minutes or so then put the cap on and snugged it down. I also turned the heat on inside and set the temp dials to the highest temp. I probably ran it for at least another 10-15 minutes until the thermostat opened but the air from the interior heat ducts never got hot. The temp gauge on the dash was at the 1/2 was point and the coolant in the overflow tank began to rise. I am pretty sure the thermostat opened up because I could feel the upper hose start to get warm from the thermostat housing to the direction of the radiator (from heat transfer through the coolant). When the coolant was just about to start bubbling/steaming out of the overflow tank I shut the engine off. I went back out about 15minutes later and starting checking hoses and coolant hard lines. The upper radiator hose was now hot, but the lower was stone cold (not pressurized and could be squeezed easily). When I squeezed the lower rad hose, coolant gurgled back through the radiator to the overflow tank, so this confirmed what I had thought about the radiator being unplugged and ok. I followed the lower rad hose back toward the back of the engine and it seemed like it was also cool or not filled with warmed coolant either. The heater core hoses (both inlet and outlet) were cold too. The lower hose from the overflow tank seemed hot and the hard line along the back of the engine where it is connected also seemed hot or very warm. I think the larger hard line that runs along the back of the engine was also warm, but it could've been from the engine heat (I couldn't really get my hand back there). Now that I think of it, it couldn't have been hot from coolant running through it because it supplies the heater core and the lower radiator hose and they were both cold.
So now I'm working my way back to where the water pump is or where the coolant exits the engine (through a water pump housing? I'm not sure, I need to look at a diagram to see how Volvo has this designed.). I forgot to mention that I have 220k miles on the car. I don't think I or any shop has ever replaced the water pump either. (I bought it with 21k miles on it.)
I think I might drain the coolant system completely and clamp off the heater core inlet and outlet along with the inlet and outlet overflow tank hoses. Next unhook the upper and lower rad hoses from the radiator and remove the thermostat, then reconnect the thermostat housing neck. Next with the engine off, I think I'll run water from a garden hose into the upper rad hose (disconnected from the radiator but connected to the thermo housing neck) and see if I get any water flow through the engine. If there's no flow, the system is plugged or restricted somewhere. If this is the case, I may move to the water pump next. If this is the problem, that sucker would probably be a mess inside. If the pump looks good or operational, I guess its down to running compressed air through the coolant port where the pump sends coolant through the engine. We have some decent weather for the next week (I'm working outside) Ben, so we better get cracking before the snow starts falling.

Good luck brother, I hope my situation helps you out a little. If you figure something out, please let me know.

If anyone else has any help for us, please let us know. Thanks again..

By the way, I'm located in Armada, are you anywhere nearby? Thanks again.

[grntrdbx]

I was looking at a short write up on the coolant lines (Coolant System Overview on a Volvo 850) by Tracy's True Soaps and this may help understand what lines go where and where the coolant ports are found. I think, in my case, I might not be able to initially rule out the head gasket. Just looking at the design, I'm thinking the ports that feed the head around cylinder 5 could possibly get plugged, maybe by debris or sediment buildup. I'll keep you posted if I find out anything.

[rspi]

Bad head gasket. Coolant systems are very basic since coolant began.

[turtlehead]

I know this is a really old post but thought I'd add to it since I had the exact same problem. I had to replace my turbo (it was blowing smoke, not related to this issue at all) and drained the coolant out beforehand. After I put everything back together I filled the reservoir with water and started it up. Within 15 minutes the car overheated and I shut it off. Over the next few weeks I tried checking the coolant level and nothing I did worked. Then I removed the thermostat housing and pulled out the thermostat, and I noticed that there was no water under it. Thinking it was a bad thermostat, I put everything back together without the thermostat and started it up. Again it overheated. This time, while it was running I took the upper hose off and realized that there was no water coming out. So I thought, either the radiator is plugged, or the water pump impeller had disintegrated. The cheapest thing to do first was flush out the radiator, so I went to home depot and bought something some PVC stuff so I could attach a garden hose to the upper radiator hose. I first pulled off the lower radiator hose and flushed the radiator. I didn't see anything but water come out, so I don't think the radiator was plugged at all. So then I reattached the lower hose and ran water through the block until it was coming out of the thermostat housing. I shut off the water and, with the upper radiator hose still disconnected, started the car. And voila, I had water coming out, obviously being pushed by the water pump.

So I conclude that my problem was, probably, that I did not have enough water in the engine block, or there was an air pocket in the water pump that was preventing it from circulating water.

In my case, priming the water pump is what fixed it. Hope this helps somebody else, it was a cheap fix and I was really surprised that it wasn't more serious.