Community Forums

Phair · 06-09-2022, 04:51 PM

Hi,
We are traveling with an old Chevy 454, on a 28' motorhome from 1991. Since Texas with more than 90° a lot of wind and some steep climb (NM, Colorado, Utah) the engine is overheating ... We removed the AC (which was not working) and added two fans (with a switch), and even like that it's still overheating.
So our 2nd guess was the fan clutch which was changed last year (around 6,000 miles ago), and even when the engine is hot, it seems to run freely ...
My questions are :
* Is it possible that the fan clutch broke that fast ?
* What is a correct speed/RPM when climbing ?

donr103 · 06-09-2022, 05:26 PM

I will just jump in.. what are the temps that you are getting in degrees? What are you using to measure temps? Are you relying on dash gauge ? Are you pulling toad?
1st.. look closely at the radiator.. not condenser.. you have to look behind condenser to see radiator and use a strong flashlights.. that area can be packed with nests and grass.. What is your trans oil temp..? some people do not realize that trans gets it's cooling from radiator.. so if trans is running hot.. so will eng.. when was last time you changed thermostat and coolant ? When was last time you changed belt and tensioner ? The more information you can give us the better opinions will follow
Good luck and keep us posted

donr103 · 06-09-2022, 05:32 PM

I re read and see you removed a/c.. so is the belt to water pump tight.. ? I am guessing here but yours must have the old style v belts and not just one serpentine belt.. I would double check belt.. is tight..
Good luck and keep us posted

Soppy · 06-10-2022, 05:59 AM

If the fan clutch is working properly , the fan will make a lot of noise. The clutch operates when the temperature reaches 210 deg. The stock gauge on the instrument panel is not very accurate. When you say overheat , is the rad boiling and are you loosing coolant or is it just running hot.

n2zon · 06-10-2022, 08:42 AM

The fan clutch can fail instantly when it fails; ours did. When you're used to the fan noise when it engages, it's very obvious when it doesn't.

Isaac-1 · 06-10-2022, 03:34 PM

If you have the stacked style radiator / oil / transmission cooler setup used on later P series coaches they are VERY prone to getting packed with dust and grime, and blocking airflow, the solution is to unbolt them slightly pull them apart and spray water between them to flush the gunk out.

1972VWbus · 06-10-2022, 06:09 PM

Quote:

Originally Posted by Phair

Hi,
We are traveling with an old Chevy 454, on a 28' motorhome from 1991. Since Texas with more than 90° a lot of wind and some steep climb (NM, Colorado, Utah) the engine is overheating ... We removed the AC (which was not working) and added two fans (with a switch), and even like that it's still overheating.
So our 2nd guess was the fan clutch which was changed last year (around 6,000 miles ago), and even when the engine is hot, it seems to run freely ...
My questions are :
* Is it possible that the fan clutch broke that fast ?
* What is a correct speed/RPM when climbing ?

1. When climbing grade did you hear the 'loud roar' from the clutch fan being engaged?

2. Do you have the (OEM) fan shroud in place?

3. When is the last time you cleaned out the exterior radiator?

4. Radiator fins in decent order (not overly tweaked or bent out of shape)?

5. When did you last service the radiator?

6. The trans cooler can be flushed without unbolting it. It will generally be mounted in front of the AC condenser off to one side (small radiator looking).

7. The clutch fan is engaged bi a small copper bi metallic coil on the front side of the clutch fan (dead center). It begins to engage when the 'radiator discharge air' temp reaches roughly 150-190F. Radiator discharge air temp is the temperature of the air that has flowed thru the radiator.

8. To make veering behind the AC condenser a lot easier get one of these...
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

9. When the engine is stone cold can you freewheel spin the clutch fan? If so, how many turns does it spin? If it freewheels easily and spins many times it is shot. Only use a GM one.

10. Check and make sure the AC condenser fan is working correctly. Wire it straight to battery. It should spin. Also check to make sure the sensor (single wire) for it is plugged in. It is mounted into the passenger side cylinder head. That fan serves more than just the AC condenser cooling. The large condenser is a 2 piece unit (AC cond./Oil cooler). The condenser fan will kick on when wired when the coolant temps reaches approx. 221F and/or when the AC press. reaches a given point.

11. As for the dash gauge. They are not very accurate for those year coaches and are often as much as 20-40 degrees inaccurate. Use either a phone ALDL app that pulls the temp reading from the ECM or a IR temp gun aimed at the upper radiator hose as close to the T stat housing as possible.

MinntoMich · 06-10-2022, 06:21 PM

If you not hearing your fan roar then more than likely its not working. Curious to know if you have an auxiliary electric fan?
I opted for an alternate (lower) temp thermostat on mine. I do know from experience that if you haven't changed or flushed your coolant the water jacket/block can fill up with a lot of crud. How is the condition of your coolant?

I "try" to travel in the cool of the morning or late afternoon. It makes a difference on how hot everything gets from the tires and hubs to the engine.

donr103 · 06-10-2022, 08:50 PM

Just wondering.. could fan be installed backwards when fan clutch was changed .. don't LAUGH it's easy to do.. I have done it.. so recheck fan is on right and recheck electric fans.. so they are working right
Good luck and keep us posted

1972VWbus · 06-10-2022, 11:23 PM

Quote:

Originally Posted by donr103

Just wondering.. could fan be installed backwards when fan clutch was changed .. don't LAUGH it's easy to do.. I have done it.. so recheck fan is on right and recheck electric fans.. so they are working right
Good luck and keep us posted

Not the clutch fan itself. It installs only one way.

1972VWbus · 06-11-2022, 02:32 PM

Here is a shot from inside coach looking forward (engine doghouse). See the fan blade orientation? The pic somehow turned left 90 degrees.

Soppy · 06-12-2022, 11:14 AM

The fan appears to be on correctly.

1972VWbus · 06-12-2022, 04:56 PM

Quote:

Originally Posted by Soppy

The fan appears to be on correctly.

That is not the original poster.

1972VWbus · 06-21-2022, 02:35 AM

To give you an actual documented idea of how inaccurate the dash gauge can be I'll post a couple pics. This was after I had replaced the upper hose, lower hose, by-pass hose, new Delco 195 T-stat...

First pic is idling just prior to driving up a 3/4 mile long hill near home. Second pic is once at top of the hill. IR readings were taken right from upper hose near T-stat.