Volvo 850 overheating

Derek · Post by **Derek** » 31 Mar 2006, 07:28

Hello,

I just aquired this car. It's an 850 Turbo wagon. It idles without overheating but as soon as you drive it, within 5 minutes the temp guage shoots up into the red. In fact while I was driving the car home I blew up the heater core from the pressure.

I've now replaced it but the car still overheats. It acts like it needs to be "burped". My question is how does one remove the air pocket on this engine. It does however seem to be circulating the coolant. Maybe not though because of how quickly it heats up and wants to blow the fluid out.

Blown head gasket? Doesn't seem like it to me.

Anybody know what's going on?

Thank you,

Derek

Post by **pfeener** » 31 Mar 2006, 13:50

Don't keep driving it until you get this issue resolved. The block and head are aluminum and you will do permanent damage to the engine if you haven't already. Two simple things to check:

1. electric fan in back of the radiator; is it coming on when the engine is up to temp.

2. check the thermostat; or just replace it. Cheap enough and fairly simple to do with the right tool. Go will need a long Torx socket to remove the thermostat housing. You can take the old one out and put it in hot water to see when it opens, but for under $20 you can just buy a new one.

The 850s don't usually have an issue with trapped air pockets. The hose on the top of the thermostat housing will normally bleed off any trapped air as you fill the system.

Derek · Post by **Derek** » 31 Mar 2006, 15:21

Thank you for the tips.

The fan is working fine. I'll check into the thermostat. The small line that goes from the thermostat housing to the plastic fill tank flows water while the engine is running. Maybe it's allowing enough water to circulate to keep the engine cool while at idle but starves it when the car revs and gets under load.

So, the thermostat sounds likely.

No sign of any water in the oil or anything like that.

Thank you again. I'll let you know what happens.

Post by **MadeInJapan** » 31 Mar 2006, 17:52

On the contrary, the from your description the thermostat sounds faulty. Which way is the water flowing? To or from the overflow tank? Stuck thermostat at closed position is what you're describing. Fortunately, for most of us, the thermo tends to get stuck at the open position when it goes bad...but not 100% of the time. Well worth checking that out as well as what's actually in your coolant.

Derek · Post by **Derek** » 31 Mar 2006, 21:09

The water is flowing from the thermostat to the overflow tank. The water has anti-freeze in it and does not appear contaminated in any way. No rust or anything.

The car had not been used much recently prior to my aquiring the car. This could explain the stuck thermostat particularly in the closed position. Sounds like that's the culprit. I'll find out soon and post my findings.

Thanks for the help

Derek

Post by **MadeInJapan** » 31 Mar 2006, 21:58

Dereck, the coolant is suppose to flow from the expansion tank to the thermostat housing and not the other direction. That's why I'm saying your thermostat is stuck in the closed position. The coolant coming from the big hose from the top of the radiator through the thermostat is also not getting to the engine (therefore it's forced upward to the expansion tank) because of this, thus causing your engine to overheat. Just replace the thermostat and I'm betting your problems will go away. They're cheap. You can get them at www.fcpgroton.com, specifically here: http://www.fcpgroton.com/volvo850cooling.htm Get the 87degree one for $9.00 plus shipping. It comes with a gasket.

The torx screws (especially the back one) is hard to get out. You'll need a torx T40 socket, but with a long stem (about 6 inches). An adaper on the end of your typical ratchet won't work. AutoZone has a kit of several of these and they come with a handle that you attach to any one of the longer torx drivers. You'll probably booger up the screw in there (I did the first time I did this), so go ahead and order a couple of the housing screws from groton along with the thermostat...only a buck or two for these and you won't be sorry that you bought them. You may have to call them to buy these screws...they aren't posted on their site, although they have them.

A point about installing the thermostat. If the screws are really really tight...spray some PB blaster on them and let them sit before undoing them. I have heard of folks wrenching the top of these screws off and you don't want to do that. In regards to draining the coolant, you really don't need to do that at all. The easiest thing to do is to either clamp off the hose coming off the bottom of the expansion tank or syphoning all the coolant out of there to begin with. I like clamping the hose. This way, you create a vacuum (like holding a finger over a straw) and when you take the thermo housing lid off to get to the thermostat you have very little if any coolant spillage. Just go to your autoparts store and buy a large flat type hose clamp. Here is this site's write-up on how to do this: https://www.matthewsvolvosite.com/tstat.php Follow whichever procedure you want.

Good luck! I'm sure you'll be on the road enjoying your Volvo in no time.

Post by **pfeener** » 01 Apr 2006, 05:49

If you decide to drain a little antifreeze out to replace the thermostat; the drain plug is on the LH side of the radiator on the bottom. You'll see it through a hole on the splash pan. It's made of PLASTIC!!!! it will break if you tighten it even a little too much. Just snug it up when you tighten it. Might not be a bad time to change out your antifreeze as well. Use the green stuff.

Post by **robert213** » 01 Apr 2006, 09:15

pfeener wrote:If you decide to drain a little antifreeze out to replace the thermostat; the drain plug is on the LH side of the radiator on the bottom. You'll see it through a hole on the splash pan. It's made of PLASTIC!!!! it will break if you tighten it even a little too much.

So that is where the radiator drain plug is, I couldn't find it earlier. Another option, it is very easy to place a rubber hose on drain petcock located on the side of engine block. I ran hose into a clear plastic juice container. I was able to reuse coolant this way.

Post by **MadeInJapan** » 01 Apr 2006, 09:45

Good idea, but if you just clamp the hose(s) shut, the vacuum created in them will keep almost all radiator fluid from leaking out of the thermostat housing when you change it out anyway. That's what I would do unless your hoses are old and you feel you might damage them. In that case, I would recommend replacing them anyway. As Robert and others have said, avoid using the plastic petcock as it is apt to break...then you're in a world of hurt....seriously.

Derek · Post by **Derek** » 01 Apr 2006, 17:46

Hey you guys are great! I haven't done the work yet as I have had other commitments this weekend but I will do all the things you suggested. I can't wait to get the car back on the road.

Thanks a lot!

Derek