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  #1  
Old 09-18-2011, 07:23 PM
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Default Tips for replacing the Coolant Temp Sensor

I need to replace the coolant temp sensor, but realized the sensor is under the intake manifold. Are there any tips on an easy way to reach it without having to remove the intake manifold?
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  #2  
Old 09-18-2011, 08:39 PM
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It is possible to remove and exchange the sensor w/o pulling the intake. Small hands and an inspection mirror a definite plus. I've tried it both ways and honestly, it is faster and less frustrating by far...to just pull the intake. You will need a new intake gasket before you reassemble which in and of itself often cures a few minor headaches.

Leaving the intake in place means you'll be fumbling around the flame trap hoses as well as the injector plug wires and grounds. As I recall, I can pull the intake without removing the fuel rail...just disconnect the ground wire from the two main rail bolts. After removing the intake nuts, the entire manifold w/ throttle spool and throttle body still attached, can be gently lifted back towards the driver's corner of the firewall.
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Old 09-18-2011, 09:28 PM
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Thanks for info. Removing the intake manifold with the fuel rail on sounds like a much simpler task than completely dissembling all of it.
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  #4  
Old 09-19-2011, 09:57 AM
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Well, pulling the fuel rail isn't really that big of a deal...the only real issue is you may be disturbing old seals that will leak upon the reinstallation. Probably the easiest fuel rail removal in the world. Still, why disturb anything you don't have to. The real PITA is if you remove the throttle spool assembly and unhook the cable(s). As I said though, all that can be left alone.
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Old 09-19-2011, 09:13 PM
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I replaced it with the manifold in place. Bad idea jeans.

My hands/wrists when I got done looked like I had done a bad job of committing suicide. Will definitely be pulling the manifold if I do it again.
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  #6  
Old 09-19-2011, 09:58 PM
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LOL! Did you notice my mentioning "small hands" in post #2? It's impossible to swap it out w/ intake in place w/o some bloodshed!!
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  #7  
Old 09-20-2011, 01:56 PM
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I've been going through the exact same thing! Couple of notes:

1. Be sure you get the right sensor. I ordered one from AutoZone and it was blue instead of black. I didn't think anything of it until I found out that black can replace blue, but blue can't replace black. There is a difference!

2. Due to the above, I've had the sensor in and out about 3 times in as many days. Definitely easier removing the manifold. You can leave the fuel rail on, but I also found that disconnecting both fuel lines at the rail helped considerably. You can fish the flame trap tubes through the fuel rail and clear the intake manifold away.
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Old 09-20-2011, 07:15 PM
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I did it with the intake in place in about five minutes. I didn't even need to top off the coolant. You'll need a 3/4" 12 point deep socket if I remember correctly. Also an extension of perfect size helps. If you are missing one of those (especially small hands), then removing the intake is a good choice. However that's when my car started hunting at idle, and no one can figure it out. I would recommend a new gasket and torque to 13-ish lbs on a torque wrench for the 13mm nuts on the manifold.
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  #9  
Old 09-20-2011, 09:55 PM
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Perfect timing for this thread. My temp gauge is not moving at all so I'm thinking I will need to replace the sensor. The inlet and outlet hoses are hot so I'm pretty sure the thermostat is working. Would this sensor being out give me a check engine light, in other words, besides giving a signal to the gauge, does it also feed something to the ECU?
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  #10  
Old 09-20-2011, 10:07 PM
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Quote:
Originally Posted by pcarnut View Post
Perfect timing for this thread. My temp gauge is not moving at all so I'm thinking I will need to replace the sensor. The inlet and outlet hoses are hot so I'm pretty sure the thermostat is working. Would this sensor being out give me a check engine light, in other words, besides giving a signal to the gauge, does it also feed something to the ECU?
No. Volvo used 2 different senders; one for the gauge located under the intake by cylinder 2 and another, referred to as the ecs, located by cylinder 3. The gauge sender is further forward and easier to access than the ecs. The gauge sender being out in no way affects fuel mixture; it merely drives the gauge. It's possible the connector is merely loose.
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Old 09-20-2011, 10:12 PM
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Quote:
Originally Posted by swiftjustice44 View Post
No. Volvo used 2 different senders; one for the gauge located under the intake by cylinder 2 and another, referred to as the ecs, located by cylinder 3. The gauge sender is further forward and easier to access than the ecs. The gauge sender being out in no way affects fuel mixture; it merely drives the gauge. It's possible the connector is merely loose.
Okay, thanks for the quick reply. Guess I'll tackle one problem at a time but I was sure hoping the gauge not working was related to the CEL. Is the gauge sensor a dealer only item or can I get one from the usual local parts people?

I checked for any codes and none came up except when I did the system test I didn't hear the EGR valve doing anything so I'm wondering if that is my next possibility.
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  #12  
Old 09-25-2011, 12:23 PM
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Titan Joe, I would have never believed you until I tried it myself! Just replaced the sensor for the second time and I tried your method. It worked! I think it helped that I knew where the sensor was and what socket to use. I've had issues with this ECT and have had to go through this process about four times in the last week. Knowing what I know now, I'd just leave the intake manifold on.
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  #13  
Old 09-26-2011, 09:45 AM
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Swiftjustice, thanks for your help. Based on your feedback I checked codes again and found I had a code on the EGR. Took a second try at looking for problems before ordering a new valve and found the vacuum hose had disintegrated and although it was still attached to the valve, there was no vacuum. Put on a new piece of tubing and presto working EGR and no CEL. Took the car down and it passed smog no problems. Now I just need to get the temp gauge working. Thanks again for everyone's input.

Last edited by pcarnut; 09-26-2011 at 09:48 AM.
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  #14  
Old 09-26-2011, 09:58 AM
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1985-1993 Volvo 240 Water Temperature Sender
This is the gauge sender. It's equally likely that it is a wiring flaw. Less likely, but still possible is the gauge itself has failed. A digital multi-meter will be your friend on this. Any decent manual will tell you the appropriate range of resistance on the sender and gauge.
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  #15  
Old 09-27-2011, 09:21 AM
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Quote:
Originally Posted by swiftjustice44 View Post
1985-1993 Volvo 240 Water Temperature Sender
This is the gauge sender. It's equally likely that it is a wiring flaw. Less likely, but still possible is the gauge itself has failed. A digital multi-meter will be your friend on this. Any decent manual will tell you the appropriate range of resistance on the sender and gauge.
Thanks, I'll do some more digging.
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  #16  
Old 11-09-2011, 04:45 PM
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I swear I'm gonna do this soon here. Shall I photo document the process for anyone???
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  #17  
Old 01-17-2013, 12:58 AM
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is there any possibility that a bad ect on my 91 230ft is causing major fueling problems... car was warming up on what has been extremely cold rocky mountain winter day...then just died , I have replaced or tested many parts already it sent an amm 121 code , then a 312 code which cleared, when I turn ignition on main pump doesnt come on... I jumpered term 87/2 and 30 pump will run, but car wont start , I replace new relay car will fire , ...idle a little then die or if I mash it to the floor it will run , but appears to be loading with fuel , black carbon fouling at tailpipe ...I placed the air mass meter on my running 940 car and it worked fine... the 940 seemingly developed fuel pump problems shortly after { coincidence ?} anyway , it has been brutally cold here at 7000 feet -20 to - 65 , I have put a new ign module, new c.p.s. switch , new relay, both pumps function under direct 12 volt power, swapped known good amm, removed /checked in tank pump checked all vac hoses , checked for spark cleaned throttle body, checked for fuel at the rail, cleaned o2 sensor ...boy that was fun with a mild Wyoming 20 mph breeze and 0 degree static temp. lying on my back ... you name it I probably did it in - 15 degrees outdoors not fun, ! my question is could this ect be causing the fuel signals to be fouled up and cause this ? from what I decipher now it could be causing , the car to have these symptoms due to improper fueling signsals ... why it set off the 121 code is a mystery, All in all I would say Ive kept a pretty good attitude ... the only thing I can think of doing is a new 967 ecu , but do you think it could be that pesky hidden ECT... thanks in advance for the help... I am a dedicated Volvo lover , I own 2 , my daughters each own 1 , I have done some truly amazing stuff with these cars , and am a minor legend in my little town for hauling some odd stuff including a small Bull Elk , 20 + foot power pole crossarms etc ... the cars are hands down the best used cars on the road please add your input thanks Ben
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  #18  
Old 01-18-2013, 12:08 PM
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I hate the Gauge Sensor even more--at least you can put a socket on the CTS. The gauge sensor base is smaller than the the plug, so you have to destroy it to get a socket on it--only an open end will do, and even then there is stuff in the way, and the brass strips easily...
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  #19  
Old 01-18-2013, 12:20 PM
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if you suspect the ECT, its easy to test with an ohmmeter... unplug the ECU and test it at the ECU pin 13 (on any LH 2.4 car), measure resistance to chassis ground (ECU pin 5) (disconnect the big ECU plug, and put the ohmmeter between pins 5 and 13 on this harness connector)

there's a resistance per temperature table here, http://www.swedishbricks.net/700900F...ECT%20Failures

doesnt' have to be exact, just somewhere in the right ballpark. cold engine will be several K-ohms (ice cold == 6000 ohms, 20C == 2300 ohms), and a hot engine will be just a few 100 ohms.

if thats what you get, then your ECT is probably just fine, you'll need to find another tree to bark at
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Old 01-21-2013, 03:26 AM
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Okay so I have searched relentlessly...to find the 1991 740 b 230ft ecu pin i.d. chart ,does anyone have a link ? Please ...and I am assuming that I check the connector side , not the ecu side ? correct ?.. this problem is really kickin my butt, I need to get this car going !Also searched relentlessly to find out what the heck the ballast resistors exact function for the injectors is, and what symptoms would a failed resistor play in my dilemma , , I rigged a trick relay with a jumper wire from 87/2 soldered to # 30 terminal, car would run seemingly correct !however as I said when I jumpered 87/2 to 30 terminal without the relay in place , pump would run ...but car would not start , when I removed the jumper and plugged in the NEW relay car would start with the fuel that the jumpered situation pumped to it ... run for a while then begin to die ...until I mashed the throttle ...then it would try to run sputtering etc until it died after about 1 minute or so , rechecked codes and I am still getting the "121 amm code, but know a "232 " code came up also . , car has new Relay, new ign, moduke, new c.p.sensor swapped o2 sensor , which I lightly sanded /cleaned , swapped a 16 valve pres. regulator etc etc etc , replaced short intercooler rubber hose coupler , Any body have any tips to offer ? thanks for your help in advance Sincerly Ben 307 780 5658
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Old 01-21-2013, 03:26 AM
 
 
 
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240, 94, 940, coolant, coolanttemperature, install, location, locatoin, radiator, replace, replacement, sensor, temp, temperature, volvo


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