Cat 3176B overheating issue

[Ricky Coon]

Hello, i am having an overheating issue with my 1995 Beaver Marquis Sapphire motor coach. It has Gillig Chassis , 365 HP Caterpillar engine with a 6 speed Allison World AT. First let me start by saying I called Gillig and although the guy tried to help he was not very helpful.

The problem:

After about 5 miles the coach gets to normal operating temperature (approx 190 degrees) and stays there for a varying distance,  could be several miles could be many miles there does not appear to be discernible pattern. The problem is it then keeps rising to approx 210 - 220 degrees stays there again for a varying time period with no discernible pattern, then goes back down to normal 180-190 degrees.

Here is what i have observed:

1. the radiator cooling motor has a slight leak not sure if its the motor of the hoses. I checked the hydraulic reservoir fluid level and it is between the full and add marks while cold.  This motor has three hoses the two larger hoses going to a 6" X 6" x 9" box. the third smaller line going back to the hydraulic reservoir. The box appears to have two wires going to what appears to be a solenoid. I am guessing this box is used to control  the fan speed?

2. the cooling fan is always on while the engine is on, never shuts off that i have noticed. Have never heard it increase in speed either.

3. There is a small coolant leak coming from a two part flange connected to the back of the water pump.


My questions:

1. What is the normal operating process for a coach of this vintage and model?

2. Should the fan be on all the time or only when it is called for?

3. Should the fan vary in speed during normal operation?

4. Is there a procedure to check the fan control mechanism?

5. Will the small coolant leak cause all these problems or is it a combination of them all leading to my erratic cooling dilemma

Your help and input is greatly appreciated, Rick

[Gerald Farris]

Rick,
First, I have not worked on you exact chassis before, but I can help with some answers. The normal operating temperature on your coach should be between 180 and 200 degrees depending on operating conditions and gauge accuracy. The 210 to 220 degree readings are too hot. The hydraulically driven cooling fan should run at idle (slow speed) all of the time until the engine needs high air flow to cool the coolant to maintain normal operating temperature. At 210 degrees and 1500 RPMs, it should sound like a small jet engine because that large fan should be pulling 30 or more HP from the hydraulic system.

Second, all leaks should be fixed. However, the leaks may not be the reason for your current overheating condition if you are positive the coolant level is full. A coolant leak will result in low coolant levels that can make the fan control inoperative because it is not in constant contact with liquid coolant if an air pocket develops. If the hydraulic fluid gets too low, it can damage the pump and compromise the power steering that runs from the same system.

If I did not answer your questions adequately, feel free to call me and I will try to help you further.

Gerald 
   

[Ricky Coon]

Thanks Gerald for taking a stab at my post i appreciate it. I have kept the coolant level topped off since i have owned the coach. Has always had a constant slow leak but until recently neither I nor the Cat repair facility in Duluth MN (great guys) have been able to identify where the leak is coming from. We performed a oil analysis and coolant analysis which showed no problems whatsoever.  So I agree the leak will be fixed but is not likely the cause of my underlying overheating issue. I believe the root of the problem is in the speed control circuitry for the cooling fan. Just not sure where to get troubleshooting information for the fan / control circuit. I could take it to a repair facility but wheres the fun in that

Thanks again

[Edward Buker]

Ricky,

The symptom of varying periods of normal temperature operation and periods of abnormally high temps gives you some long enough intervals to possibly measure and see what is different between the two conditions.

With various measurements on fixed locations between the two conditions you would likely get some good clues.

A hand held infrared gun (thermometer) could measure across the radiator face during normal and under high temp conditions to see if it is uniformly hot or some indication that flow is being affected. You could also measure the thermostat housing, cooling hoses to and from the radiator, as well as the block under both conditions at idle and a fixed rpm while stopped.

https://www.amazon.com/Etekcity-Lasergrip-774-Non-contact-Thermometer/dp/B00837ZGRY/ref=sr_1_2?ie=UTF8&qid=1479959092&sr=8-2&keywords=infrared+gun

The other tool is a hand held anemometer. You can place this in several fixed locations at the radiator face to see at idle and at a fixed rpm (say 1500RPMs) when temp is normal vs when it is hot and see if air flow is changing. I have used one of these units and characterized the 10kw Onan generator radiator air flow with a slipping belt and a good belt and I could easily see in my case the air flow variation that was causing an overheat shut down.


https://www.amazon.com/HOLDPEAK-866B-Digital-Anemometer-Temperature/dp/B00ZHKWCP4/ref=pd_day0_86_3?_encoding=UTF8&psc=1&refRID=7FA7N2J3Q5NWD5738APF

These units are inexpensive and it would take a little bit of a learning curve to use them. If you create a good measurement matrix, with repeatable measurement locations, under both conditions it should yield some clues. When you simply have a constant overheat issue, that would seem to be more difficult to diagnose, your case seems worth a try. Whatever time and money spent on this effort could possibly save you a lot of hrs at a shop trying to diagnose this issue.

There is also a reflective tachometer using a laser and reflective tape placed on the fan blade to get a direct RPM reading if you have safe access. This can read at up to 20 inches away per the write up. This may be a better measure than an anemometer.

https://www.amazon.com/Neiko-20713A-Tachometer-Non-contact-Accuracy/dp/B000I5LDVC/ref=sr_1_2?ie=UTF8&qid=1479960001&sr=8-2&keywords=hand+held+tachometer

Hope this helps.

Later Ed

[Dave Atherton]

Ricky, sounds like your problem and age of the Cat 3176 engine, There is restriction in the engine
Oil cooler or sticking check valve at engine oil cooler. At present working on a piece of off
road equipment with Cat 3176 engine with heating problem and problem was located with
engine oil cooler replaced engine oil cooler and heating problem has stopped. This is why
Oil and coolant samples did not detect any problems. Dave Atherton Retired Cat Mechanic

[Ricky Coon]

Thanks Edward I will take your thoughts into consideration. Dave is the oil cooler the horizontal tube located behind and connected to the water pump? If so coincidentally the connection between the water pump and "oil cooler" is the location of a coolant leak I recently discovered. Is the check valve you mentioned located within the oil cooler or is it a second item to be replaced? Thanks for every ones assistance, Rick

[Dave Atherton]

Ricky, view from upper right rear of engine should be a horizontal tube with oil filter base
below tube connected by 4 bolts and two o-rings. The water leak is a good sign problem
Is located in oil cooler. One thing Dave would suggest in helping to assist you, what is your
engine serial number that is very important. 1995 3176 engine is it a A model or B model.
Information that Dave is relating to Cat 3176 B model S/N  9CK prefix. If your engine is a
3176 A model than different direction will be required.  Cooling fan always on will need to
remove ECM harness connector J1/P1 locate PIN number 28 ( cooling fan relay ). If you need
Technical information and part numbers after getting correct engine serial number Dave
can provide information on Ask Dave on the Beaver Amb forum or contact Tim Bentley the
Site should be working. Dave Atherton Retired Cat Mechanic