Hi all,

Just acquired my first Volvo, a super clean 1986 240 wagon. I am in love! I could see myself never owning a different make/model of car as I am having so much fun with this one. The car came with every service record since the day it was bought by an elderly woman. Its been impeccably maintained. was garaged since day one and is in immaculate condition. It has 248,000 miles and the original motor and automatic transmission.

An issue has cropped up and Im hoping that those with more experience can help a girl out. A week after buying the car, the temp gauge shot up almost into the red. It has been a very intermittent issue. Two weeks straight the temp gauge is at 9 oclock. Then it shoots up into the red randomly on my way to work (after sitting all night). Then when I leave work in the evening, its once again fine and stays at 9 oclock. The thermostat was just replaced two days ago. First time it was ran after the thermo change, it again jumped up almost into the red.

Looking back through years of service records, this car has had a history with this. Every time the temp jumped up into the red (again, very intermittently), the previous owner would run the car to the Volvo dealership right away. Every time, they could never recreate the high temp even after running it 10 or more miles and their answer was to just put a new thermostat in.

Im wondering if its actually overheating or if its more of a sensor or gauge issue? If I blast the heater in an attempt at bringing the temp down, sometimes it brings it down slightly and sometimes it doesnt seem to help at all and the gauge just hovers right about 11oclock no matter how long I leave the heat on. Of course I dont want to risk actually overheating the car so Im really wanting to resolve this issue once and for all. As a temporary fix since Im only driving the car back and forth 4 days per week at a local job, the new thermostat has been entirely removed and Im just running it without one.

Any ideas? I dont know if this helps but my fuel gauge seems to bob around too much as well. It will go from a 1/8 tank to below empty and back up again all the time even when Im just driving straight down the highway. Even when its BELOW empty on the gauge, the car will only take 10-11 gallons of fuel (I think its a 15 gallon tank?) so Im assuming the gauge is off.

My dad mentioned something about a sending unit and I also found online an instrumentation voltage stabilizer compensator board through IPD and am wondering if this is what it needs?

Any ideas?

Thank you so much for your time,

Shannon

 

frankly, your symptoms sound to ME like a sticking thermostat, especially since they started right after it was replaced. do you know if they used a 'real' volvo part or an after market generic one?

the temp compensator is on the back of the instrument panel, and its function is to keep the needle dead center if the temp is anywhere in the normal range... IPD sells a kit to replace it with a simple jumper so the needle responds linearly with temperature.

the temp sender for the dashboard is on the side of the engine block under the intake manifold... theres probably 3 sensors in a row there, one is the antiknock sensor, another is the ECT (engine coolant temperature) sensor for the ECU and ICU (injection and ignition control units), this one has 2 wires, and one has a single yellow wire and is for the dashboard temp sensor. these temp sensors are variable resistances to ground, about 2k or 3k ohms when the engine is cold and about 200 or 300 ohms when the engine is normally hot.

I imagine you could disconnect that yellow wire, and connect it to the center tap of a 3k or 4k potentiometer (variable resistor), with one end of the 'pot' connected to ground, then as you turn the pot, the needle should move correspondingly. it will have a big 'flat spot' in the middle due to that temp compensation board where the needle will stay centered while you move the pot through the middle of the range. I haven't had to actually try this, but I wouldn't be surprised if the needles response to changes would be slow... and of course, the ignition has to be on for this test to work.

 

Thank you pierce. I will pass on this info to my boyfriend. Just an fyi...the car is behaving the same exact way with the new thermostat as it did with the old one we pulled out. We replaced the old one with a Volvo OEM replacement.

Shannon

 

You can tell your thermostat is working (opening) if your upper radiator hose is hot to the touch from the coolant being pumped out of the engine through the opened thermostat.(when the engine is cold the thermostat is closed and the coolant is recirculated between the pump and the engine until it gets hot enough to open the thermostat and permit flow to the radiator for it to be cooled. I don't know about leaving the thermostat out altogether. for one thing it'll take longer to warm up. You might want to google that one or post another question on the forum.

The Bentley manual gives a quick test to check your temperature sensor which causes the gauge needle to rise. There's a thin wire, yellow in my '89 240 on the driver's side of the engine, about the middle, attached to the sensor at the top of it. Pull the connector at the top of the wire from the sensor and ground it to the engine block. I used a little clamp to hold the connector to a metal strut in front of the sensor. Turn the ignition on. If the gauge needle goes to the top of the gauge "then the sensor is most likely faulty" I'm quoting the manual. A sensor is 25-30 dollars. If the needle doesn't move then it's the wiring or the gauge that's faulty.

If you change the sensor, do it with a cold engine and have the replacement at hand since coolant will come out once you remove the old one and you don't want to get burned.

This is all new to me since I just had similar problems and have been working through them with the help of the manual and much from the good folks on this forum. Best wishes.

 

Overheating is nothing to play with as it destroys Volvo engine more than anything else. Still, yous symptoms point to a bad gauge, and that IPD COMPENSATION board is what you probably need. I'd take that thermostat OUT just to make sure...

 

I would follow pierce's instructions with one modification--I'd remove the temp. compensation board, if you are already going to be digging in that far. Instructions are here (https://volvoforums.com/forum/volvo-...g-57985/page2/)
I'd only do it on a temporary basis (use alligator clips or something instead of soldering the two poles together), but it will eliminate another variable. If you get steady movement, then your board may be at fault. If you still have trouble, the gauge is likely the culprit.