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1987_345 · 09-02-2009, 07:42 PM

I have a 1987 345 and am leaving on our first trip with the jeep in tow this friday afternoon. During the test tow we just got back from, the temp got just over 220 rather than running around 215 as usual. The auxillary fans up front never came on even thought eh HOT light came on briefly. Does anyone know what turns the electric cooling fans on and if there is a manual switch somewhere. Thanks

overlander63 · 09-02-2009, 07:46 PM

I think on that one there is a sensor, a relay, and the ECM involved. You could have a blown fuse, bad relay, bad wires or connectors, or a bad sensor. I would check the "easy" stuff first, like make sure there are no blown fuses, and the fans are connected and spin freely with your hand. You could have a bad ECM, but it is rare.

arodriguez60 · 09-02-2009, 08:11 PM

also check the coolant level.If the sensor is not touching coolant.It willget a false reading. It could be an air pocket or just low coolant. Check it first

sharptalk · 09-02-2009, 08:59 PM

Quote:

Originally Posted by 1987_345

I have a 1987 345 and am leaving on our first trip with the jeep in tow this friday afternoon. During the test tow we just got back from, the temp got just over 220 rather than running around 215 as usual. The auxillary fans up front never came on even thought eh HOT light came on briefly. Does anyone know what turns the electric cooling fans on and if there is a manual switch somewhere. Thanks

Haven't even gotten out on the road yet in mine. We are waiting on awning parts from zipdee.

Also, the ac needs a new compressor and I have been offered a replacement of the same r12 or for $351 including labor or an r134 for $456.

As far as our radiator, here is what they found out-
ROAD TESTED AND FOUND ENGINE TEMPS AT 220+ DEGREES. CHECKED FAN CIRCUIT AND FOUND CLUTCH FAN WITH
NO DRAG INDICATING CLUTCH IS BAD. IF NO RECORDS ARE AVAILABLE FOR RADIATOR HISTORY IT WOULD BE
RECOMMENDED TO PULL RADIATOR AND HAVE NEW RADIATOR INSTALLED AND NEW FAN CLUTCH BE INSTALLED.
WHILE WE ARE IN THE AREA A NEW ENGINE THERMOSTAT SHOULD BE INSTALLED AS WELL. TEST TEMP SENSOR IN
RADIATOR AND FOUND AT 209 DEGREES SENSOR NEVER GROUND AND WOULD NOT TURN AUX FANS ON.
RECOMMEND NEW SENSOR AND/OR MOVING CIRCUIT TO A/C SIDE AND BE CONTROLLED BY DISCHARGE PRESSURE.

Price-$2750.

Karen

1987_345 · 09-02-2009, 09:23 PM

Goodness. Seems awfully expensive. This bus is stretching the limits of my mechanical aptitude! I was hoping I could simply find a manual switch that would work. Oh well, time to put on my detective hat

1987_345 · 09-02-2009, 09:25 PM

That year model has an ECM?

overlander63 · 09-02-2009, 09:26 PM

1987? It should. If it's fuel-injected, it definitely has one.

1987_345 · 09-02-2009, 09:36 PM

Thanks Terry. It's carburated. I will check the ECM. Also I read on another thread to check the thermostatic switch they said was located somewhere on the passenger side head. I could also parrallel wore in a manual switch at that point if I choose to. Do you agree?

ROBERTSUNRUS · 09-03-2009, 12:31 AM

Hi, let me paint you a picture so you can see what is really going on with your cooling systems. Note: all systems have some variation, but same basic theory. [from GM mechanics school]

(1.) Water boils at 212 degees

(2.) The boiling point of water raises under pressure. At 3 degrees per pound.

(3.) A 15 pound pressure cap will give you 45 degrees more.

(4.) And only under pressure, a 50/50 mixture of coolant will give you another 30 degrees.

(5.) An engine thermostat [160, 180, or 195] most common, is to hold the engine at or close to a minimum temperature.

212 + 45 = 257 + 30 = 287. In proper condition, your engine could run as high as 287 degrees without damage. Damage happens when the coolant actually boils out of the system, not when the gauge reads hot.

Electric cooling fans usually turn on at or near 220 degrees. Most fan clutches are tight when cold and when a higher temperature is reached. [ever notice that extra roar under the hood when it's really hot out, that's the fan clutch fully engaged to cool your engine down] Other than that, your fan clutch will not have a lot of drag on it. Guessing about your cooling system ends up with a lot of money spent for nothing. Running 220 degrees is normal and nothing to worry about on most vehicles made in the 70s or later. Changing to a lower temperature thermostat than the one made for your vehicle will do two things. (1.) just take a little longer to get to the point of over heating if that's the case. (2.) Tell your computer that your engine is not up to running temperature yet so keep the fuel mixture richer. [waste more gas]

ROBERTSUNRUS · 09-03-2009, 12:40 AM

Hi, I can't count the times I have talked to people, or read about people concerned about a 5 or 10 degree increase in running temperature and all the money, time, and parts spent for nothing. Buy yourself a basic automotive theory book and read it. Then tell Bob how much money you saved.

1987_345 · 09-03-2009, 06:06 AM

That easies my mind considerably. So I shouldn't be concerned if the HOT light flutters on from time to time with the temp reading 220-240, assuming all else is good? It is full of 50/50 coolant, water pump is pumping great, and it has a new 195 degree thermostat. This website has been a Godsend to us, Thank-you again, Kenneth

ROBERTSUNRUS · 09-03-2009, 11:13 PM

Quote:

Originally Posted by 1987_345

That easies my mind considerably. So I shouldn't be concerned if the HOT light flutters on from time to time with the temp reading 220-240, assuming all else is good? It is full of 50/50 coolant, water pump is pumping great, and it has a new 195 degree thermostat. This website has been a Godsend to us, Thank-you again, Kenneth

Hi, I would try to find out why the "HOT" light flutters at times. Could be a defective temp sender or a bare wire to the sender touching a ground source intermittantly. The "HOT" light as you call it should come on at a certain temperature like maybe 262 degrees.

From GM specs in the 70s:

Water boils at 212 degrees.

A 15 lb cap/system would increase this to 257 degrees.

The overheat [TEMP] light was set to come on at 262 degrees. ***

With a 50/50 mixture of coolant + 30 degrees for total of 287 degrees.

*** Therefore, if you ran staight water in your cooling system, it could all boil out at 257 degrees and the TEMP light would never come on. [burned up engine]

1987_345 · 09-07-2009, 07:16 PM

Thank-you. Very interesting. I need to check and see how my rad cap is rated. Anyway, we just got home and had a really nice uneventful trip, except the icemaker went on the fritz. The engine ran like a top, even pulling the jeep. If I was on flat road or going down hill, everything was great. Going on an incline about 40% of the time the temp would climb, the HOT light comes on and the fan clutch locks up to cool it back down. Sometimes the clutch would kick in before the HOT light came on, but in any event according to the guage it never got to the 260 mark and we ran 65 - 70 the whole way. I probably also need to get the fan ckutch checked out. I think I am going to put some headers on to try and get some heat away from the engine a little better. Thanks for all of your help. Kenneth

sharptalk · 09-07-2009, 11:07 PM

We're hoping to have ours back from the mechanic by the end of this week so we can take our first trip. I can't believe it's been in the shop since I bought it on June 24th.

Howard Lefkowitz · 10-18-2009, 12:03 PM

On most of the 345's the two small fans, right up front, are for the Air conditioner system and do not run unless the A/C is on. A much better configuration is to rewire the fans to a dash mounted switch. Disconnet the temperature sensor and insert the switch. That way you can turn the fans on any time the engine is getting warm. I ran this way for almost 20 years and never had any over-heating problems. I always had the fans on in the summer or in the mountains and off during the winter. This also improves gas mileage since the main radiator (horsepower eating), clutch type, cooling fan runs much less.

ScrapIrony-2 · 10-18-2009, 10:56 PM

We run 210-220, climbing the passes out of Silverton on a 'warm' day...granted, we're doing 15-25 mph, and manually shifting from 1st to 2nd a lot, but we also have auxiliary fans(2) mounted in front of the radiator...some PO took care of us before we bought it...m

dljosephson · 10-19-2009, 08:00 PM

Our turbo diesel 310 had the fan replaced with a dual electric Flex-A-Lite unit, and I would recommend it. List price is crazy but Summit Racing had them in stock for about $220 including controller, temp sensor etc. One problem to look out for, they suggest that you wire the two fans in parallel through one fuse. In mine, the PO did this and when the engine overheated and toasted one fan, it shorted out, blew the fuse, and that stopped the other fan too. Moral: wire the two fans separately to the controller, with one fuse for each.

jhenry · 10-19-2009, 09:02 PM

Howard on my 1988 454 it runs at 210 -220 and the fans come on to cool if it goes higher. I could be wrong but I do not think these fans need the A/C on I have yet to use my A/C, they are on a seperate! Jonathan

ScrapIrony-2 · 10-19-2009, 09:15 PM

Quote:

Originally Posted by jhenry

Howard on my 1988 454 it runs at 210 -220 and the fans come on to cool if it goes higher. I could be wrong but I do not think these fans need the A/C on I have yet to use my A/C, they are on a seperate! Jonathan

A common problem with the 345 is that the cable that changes heating to ac will quit activating from the inside dash slide...it's a hassle, but if you go under the hood, behind the flap on the left(passenger) side is the cable, and you can manually switch from one mode to the other...if you hit overheat times, switching to dash heater will get you further down the road, not cool, but a serviceable remedy...m

bkahler · 10-29-2009, 07:37 AM

Our 310 with the 454 typically runs about 195 degrees towing our race car trailer or not towing. Sometimes it gets slightly above 200 but that only seems to happen when the dash voltage meter drops to 12 volts or less (there is a wiring problem under the dash that I need to resolve). I've verified that the gauge is accurate using a laser temperature reader. The engine is a 454 factory crate engine that has 20,000 on it.

Needless to say I'm happy with this situation

Brad