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RWD - B 20 thermostat recommendations

Volvo RWD 140-160 Forum

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B 20 thermostat recommendations 140-160

I was out and about last night and was driving around with the heater on max since temperatures took a big nose dive Sunday night. I had a short section at highway speeds (100 km/hr) and noticed that my engine temperature gauge had dropped to just a little bit over 70 C after about 6 km (its an aftermarket gauge with numbers!). Outside temperatures were probably around - 6C so not incredibly cold. When I reduced speed to urban driving the temperature started to climb back up; but, it never reached its typical operating temperature which is usually around 85-87 C (its the 82C opening thermostat).

I am thinking that the thermostat gasket is leaking or the thermostat is no longer closing. Whether its the gasket or the thermostat, its getting a new version of both. I have to lower the fluid level to check so I am having the parts on hand ahead of time so I don't have to do it twice. I remember reading a lot of opinions on good versus junk thermostats for the B20. What is the received wisdom as to what is acceptable; Stant, Gates, Wahler, Beck Arnley .....?





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B 20 thermostat recommendations 140-160

142Guy, did you ever get the operating temps up with the 82 deg thermostat? In my 1800e with B20 I had a thermostat sticking closed but gauge never went above about 1/3 . I flushed with a cleaner several times, new water pump with cast impeller and new 82 Wahler. Now I only get about 1/8 of the range on the gauge. I tested the stat and it’s working as it should. I tested the gauge sender resistance and it approximately matches the specs.

Thinking engine should get hotter , al least show hotter on the gauge.

Welcome your response and responses from others.

TIA.





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B 20 thermostat recommendations 140-160

Its summer now, so I have no problem getting the engine temperature up to the correct operating temperature.

If you think the temperature is running low, take the fill cap off the radiator, siphon a little coolant out to make room and then start the engine and let it come up to temperature. By looking in the fill cap, you should be able to tell when the thermostat opens. When the thermostat opens, stick a thermometer in there and measure the temperature. If the coolant temperature is around 82 C and your gauge is reading 1/8, you know you have a problem with your gauge.





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B 20 thermostat recommendations 140-160

A rather protracted follow-up on this thermostat question. We had a rather dry winter here so conditions dried early allowing a resumption of the vintage Volvo driving season with air temperatures that were definitely on the cool side. Same thing as mentioned on my very first post, driving at around 80 km/hr with outside temperatures in the -5 C range, the dash temperature gauge is reading in the low 70 C range.

It was a nice day today so I decided to pull the thermostat and check its operation. The thermostat is a Calorostat 82C. I did the immerse in water bath test with a thermocouple to measure the temperature right inside the top part of the thermostat housing. The thermostat starts to open around 81-82 C and is definitely as open as it gets by 90 C. So, the start of open and fully open temperatures appear to comply with the values for the type 2 thermostat in the Volvo service manual.

I let the temperature of the bath drop slowly and the thermostat does not appear to go fully closed until about 78 C, so there does appear to be a little hysteresis or the thermostat is just very slow to respond as the temperature is dropping. Out of curiosity, I checked the depth of the by-pass tube and the movement of the flap on the bottom of the thermostat and the by pass is open when cold and definitely sealed off when the thermostat is at 90 C. It was not practical to determine at what temperature the flap would close off the by-pass because as soon as you pull it out of the bath the thermostat temperature starts dropping and the flap starts moving.

With the thermostat in the closed position I pulled it out of the bath and confirmed that the center plate is closing tightly with the surrounding flange. So, with the exception of the jiggle valve there is no material leakage through the thermostat itself. I examined the thermostat gasket and there were no obvious signs of leakage around the gasket.

I am left with the conclusion that the thermostat is operating as designed and that I do not have an obvious leakage problem. I am further left with the conclusion that if you are running the heater at max on a really cold day at speeds over 80 km/hr you will struggle to meet the design operating temperature (82 C - 90C) for the engine. Since the measurements suggest that my coolant temperature was running below the fully closed temperature of the thermostat, the old school thought of putting in a hotter thermostat would not appear to offer a solution. I speculate that on the 140, at highway speeds there is enough cold air flow through the rad and the engine compartment that convective cooling of the engine block by ambient air combined with the interior heater operation is preventing the engine from maintaining its design temperatures.

Volvo used to sell cold weather black vinyl closures for the 140 that would clip on to the front grill. the closures had little flaps you could open for warmer day operation. I think these probably worked because they reduced air flow through the engine compartment and convective cooling of the block. If I want heat on cold days I think I am going to have to find one of those old grill covers.





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B 20 thermostat recommendations 140-160

Good luck in finding one of the original grille covers. Back in the day, it used to be common to use a piece of cardboard in front of the rad. It would be customised with a few holes to balance the flow v obstruction according to how cold it was. With snow and rain, they could have a rather short life so anyone a bit handy would then upgrade it to a piece of weatherboard or even aluminium. Alternatively, some cooking foil can be moulded into the grille. Cheap, easy and customisable. I've seen covers made from perspex that were shaped to cut off about 90% of the flow and held on by a couple of screws with back clips. Those looked very neat. Imagination is all you need.
It was also normal back then to have winter/summer oil changes as well as winter/summer thermostats. In some climates that is still viable. Modern oil can cope with it but a quick change of thermostat is easy and you can reuse the alternate thermostat each year until it looks a bit suspect.





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B 20 thermostat recommendations 140-160

Big rigs use radiator blankets in cold weather.

The early 122 and 544 were set up to have a "window shade" style of blanket that used 1 of the old school tubular spring loaded window shade mechanisms and it could be raised and lowered via a chain that ran inside the car to the center of the dash.
--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com





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B 20 thermostat recommendations 140-160

My brand-new '65 544 had the chain-operated, window shade feature, and I used it on cold mornings for a faster warm-up. Prior to buying the 544 I had a '54 Chevy when I lived in Cincinnati. In the winter I would remove the fan completely, & put it back on come spring-time. The only time the temp. needle rose above normal was when I had to wait for a slow moving freight train.





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B 20 thermostat recommendations 140-160

What happens if you let the car idle for a good, long while....say 30 minutes? If the temperature never goes above 82C, then I would suspect that the thermostat is "stuck" open. But if you are driving short distances in cold weather (you mentioned that it had recently begun snowing), it is entirely possible that the engine is just not getting warm enough to register the temperatures you expect to see on your gauge. Highway driving at a steady rate is easy on the engine and only requires a handful of HP. You are also, in these conditions, moving a large amount of very cold ambient air around and about the engine as you move down the road.





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B 20 thermostat recommendations 140-160

On the test I did this morning the car was just idling ( I was doing a little refining on my cold start and warm-up enrichment tuning). The coolant temperature on the front of the head sensor came up to 81 - 82C and then sat at that temperature. The back of the head (dash gauge) temperature rose slightly higher and changed a bit when I opened and closed the heater valve. At idle, opening and closing the heater valve did not seem to have any effect on the front temperature sensor.

I have had this car since Gerald Ford was the US Pres and I used to drive it in really cold temperatures (-40 C). Of all my friends in university and post university my 142 was the winter go-to car because it had the best heat in the winter. I realize that the OEM temperature gauges tend to be desensitized in their normal operating range; but, in really cold weather my recollection was that the needle was pretty much where it was during warm weather and the needle pretty much always stabilized at that same spot when I opened up the heater valve on cold days.





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B 20 thermostat recommendations 140-160

My hat is off to you, sir, for having the dedication and resolve to keep your "brick" on the road for 40+ years. I have always liked the aesthetic of the 140 series. The 240 is rather ugly by comparison (although still easier on the eyes than many "modern" cars).

I am starting to wonder if your's is not a sender or gauge issue. Certainly, replacing the tsat is straightforward enough that it wouldn't hurt. But seems like a variance this small may not br worth the trouble, unless you consider it preventative maintenance and if it happens to fix the issue, well, that is a bonus. :)





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B 20 thermostat recommendations 140-160

I am fairly confident that the dash gauge is correct within +/- a couple of degrees.

The snow looks like it will be gone in short order if the cloud cover dissipates so I may have a chance to road test by Friday. If I get out on the highway and both the front and rear temperature measurements are running around 70 C with the heater on, that is a significant issue as that low of a temperature will affect the operating efficiency of the engine.





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B 20 thermostat recommendations 140-160

If the upper radiator hose is getting warm/hot before the engine reaches its expected operating temperature it's a hint that the thermo is stuck open.
--
Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)





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B 20 thermostat recommendations 140-160

I did the hand on the upper hose experiment this morning. I tested at the hose end on the rad tank to reduce the effect of heat conduction to the hose from the head / thermostat housing. The hose remained cold during warm up until the temperature measured at the old D jet sensor hit about 70 C and then the hose and the side tank on the rad started warming up.

It would appear that my thermostat is not stuck open; but, is opening sooner than it should. I am pretty sure that I have the 82 C thermostat and the service manual says that it does not start opening until 81 C. It seems like mine is opening around 71 C. That would seem to jive with my highway temperatures that bottomed out just above 70 C on the dash gauge.





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B 20 thermostat recommendations 140-160

Good point. I will have to check that on my next cold start.





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B 20 thermostat recommendations 140-160

Check the gauge 1st, i.e. clean the conection on the sender and tighten that up, then check using another gauge, preferably one of the laser guided device.

If the engine goes from ambient temperature to operating temperature with in 2 to 3 miles of sensible driving, then I would find it hard to pull it out.





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B 20 thermostat recommendations 140-160

I have a B20E with a Megasquirt retrofit so I am able to read the front Djet sensor on my laptop. Normally in the summer when the car is moving the front sensor reads around 84 - 87 C and the back sensor reads 1 - 2 C warmer. The back sensor will rise about 8 - 10 C higher if stuck idling at a long stoplight on a hot day. As a result I think that the back sensor and gauge are reading within reason.

Woke up this morning to a nasty surprise of a blanket of white wet sticky stuff outside making for packed ice on the roads which the 142 doesn't do. As a result I couldn't confirm the front and back of head temperatures while driving. I did do an idling test and the front of head temperature came up to around 82 C and the back of head temperature was around 87 C. Turning the heater valve and fan on to full caused the back temperature to drop a couple of degrees; but, there was no significant change in the front temperature (bounced from 81 - 82 C). I have an electric rad fan and the fan never started up.

Since I think my back gauge is reasonably accurate and if anything tends to run a little hotter than the front of head temperature, I think the 70 C is an accurate temperature. The service manual says that the thermostat should start opening at 81 C and should not be fully open until 90 C. With a coolant temperature of 70 C the thermostat should be fully closed with no / minimal water flowing through the rad. At highway speeds with a completely closed thermostat I would expect the engine to be generating enough heat to drive the temperature above 70 C.





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B 20 thermostat recommendations 140-160

How was the heat inside the cabin? Don't forget the heater core is basically a small radiator and will lower the engine temperature too.

In case you want to change your thermostat, I suggest using a Calorstat, Vernet or Wahler.
--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com





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B 20 thermostat recommendations 140-160

Heat inside the cabin was good - 70 C coolant still provides a fair amount of warmth, particularly when the outside is only -6 C.

I recognize that the interior heater provides additional engine cooling. However, I don't think the interior heater would be large enough to meet the engines complete cooling requirements with an ambient of -6 C. I would have expected that the thermostat would have closed up to restrict flow to the radiator to restore the temperature.

The Volvo Service Manual provides no information on the direction of coolant flow through the heater system. From the external construction of the coolant pump and the location of the heater valve, I deduce that the direction of coolant flow in the heater circuit is out the back of the head, through the heater valve and heater core and then back to the pump. If that is correct then I would expect that the thermostat should be able to close down enough to keep the temperature at the front of the head around 82 C and the back of the head is normally a little hotter than the front (I have a B20 E and can read the old D jet sensor at the front of the block). If coolant flow is in the opposite direction and going through the heater core before it enters the back of the head, then the coolant entering the back of the head could be below 70 C and is mixing to give the dash sensor the approx 70 C reading that I am getting. If that is the case, then this is a non issue.





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B 20 thermostat recommendations 140-160

Hi, not clear to me your routing of the heater hoses. I’m not familiar with 140’s but on 122’s and 1800’s the routing is out of the back of the head, to the inlet of the heater core, then from the outlet of the heater core to the valve. From the valve to the long pipe that connects to the water pump. I have a hard time imagining that a B20 140 would be different.

No idea if this could have any effect on how hot the engine gets, but thought I’d point this out.

Will be interested in hearing when you get the problem sorted.





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B 20 thermostat recommendations 140-160

Seems like the heater circuit changed between the Amazon / 1800 and the 140. The 140 definitely has the valve between the back of the head and the heater core. I expect that the direction of flow would be the same.

Went looking for a Wahler thermostat locally - not to be found. Looks like I may have to give IPD a go as they are the only vendor that I have found that actually specifies Wahler.





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B 20 thermostat recommendations 140-160

Forget ipd, get one from Planetman, support someone who actually cares.

My old Wahlers actually have an adjustment screw, get a new one and keep that old one as a spare.





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B 20 thermostat recommendations 140-160

Interesting note about the adjustment screw.

My problem does not appear to be a leaking or stuck open thermostat. A little on-vehicle testing indicates that the thermostat appears to be opening a little bit above 70 C. The factory service manual specifies that the 82 C thermostat does not start to open until 82C. I am pretty sure I have the 82 C thermostat. That is what the box said; but, I must admit that I probably did not check the markings on the thermostat before it went in.

Have you ever checked to confirm the opening temperature for your Wahler? If the Wahler 82C starts to open at around 70C then there is no up side to putting a new whaler in.





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B 20 thermostat recommendations 140-160

Never checked acurately. Always been happy with the original gauge swinging straight to 1/2 way across. According to the greenbook this is 85°. I'd strip the wire back a bit, tin it and crip a new end on it and check it again. The D-Jet sender connectors are screwed on + I think the D-Jet wiring harness is better quality than the wiring harness has, unless you replaced that with new stuff(even better).

Have you pulled out the thermostat and looked at? Don't pull the rubber seal off and you can stick it back in again as is. If sealant is needed, Hylomar is my 1st choice there, 2nd choice is Loctite's purple gasket eliminator, that's the one I use on the rear crank seal housing and timing cover instead of the thin gaskets you would get in a sump set.





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B 20 thermostat recommendations 140-160

I have an aftermarket temperature gauge with a transducer using what looks like a Delphi plug - so no stripping and tinning. The D jet sensor on the front of the head uses a 2 pin plug type connector (identical to the fuel injector plugs). The plug, pins and wiring to the D jet sensor were replaced because of deterioration on the wiring insulation at the plug end. So, all connections are in good order.

Temperature this AM was around -20 C, so no pulling the thermostat just yet. It is supposed to warm up to around +6 C on the weekend (go figure!) so I may pull it out then, inspect and maybe do a hot water bath test.





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B 20 thermostat recommendations 140-160

142 guy wrote--"The 140 definitely has the valve between the back of the head and the heater core. I expect that the direction of flow would be the same." I wouldn't be so quick to make a blanket statement about the 140 heater flow. You are correct that the pressure side (feed) is from the elbow at the back of the head--and the return is to the pipe going to the back of the WP. BUT -- during its production run I do know they changed things a bit regarding the hoses. Heater hoses for the earliest 140s (I don't know --maybe up to '69 or'70?) are different than the later ones. I think one set used the valve to block coolant from entering the heater core and the other path blocked its return. -- Dave





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B 20 thermostat recommendations 140-160

It would seem like that is certainly a possibility. The parts manual lists 2 different sets of part numbers for the heater hoses and based upon the associated chassis numbers it looks like that change occurred between 1968 and 1969.





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B 20 thermostat recommendations 140-160

You have that right-out from the back of the head-then return to the pump.- Dave





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Wahler X2 140-160

All my good old ones are Wahler, 40+ years old.





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