# 85 HRC W/454 Overheating



## alcusmc (Jun 4, 2006)

On a return home trip last year my engine heated up to 205 degrees and for years it has run around 195. The first thing that I did  was change the thremostat and the hoses.. no change still 205 to 210. Installed new larger radiator and removed the fan clutch and installed two large electric fans on the radiator and one on the a/c condensor. No change.
Removed the heads and had them checked for cracks and none were found.. Reinstalled heads and no change in the temp.. I have checked all brakes and none of them are dragging.. On several occasions I have talked to the GM Techs at the factory and they said that it may be a clogged heater core.. bypassed heater core and no change in temp.. If I maintain a speed of 55 the temp stays around 205 to 210. If I go fasters the temp will climb up as the speed increases.. I am out several bucks on this problem and it is stll with me.. If anyone has any suggestions at all I would appreciate hearing from you.. The next option is to go to a new 502 crate engine.. but I only have 41000 miles on the coach and I do not want to get rid on it..
Thank you for your time and help..
alcusmc


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## kg5388 (Jun 4, 2006)

85 HRC W/454 Overheating

pull and double check the thermostat you may have a bad one or the incorrect one try running it without one and how bout checking the timing if its not advance or retarding as needed that could be the reason the faster you go the hotter it gets if you have vacumm advance then the diaphram could have gone bad or the movement is stuck or an advance weight might have stuck or broke in the distributor or a bad vacum line or bad vacum line to trans modulator valve


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## Krazeehorse (Jun 4, 2006)

85 HRC W/454 Overheating

Do you have an external oil cooler on the tranny?  If the atf is running through the radiator that might be the variable that changed.


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## alcusmc (Jun 5, 2006)

85 HRC W/454 Overheating

Krazeehorse,
Thank you for the reply, I do have an aux. trans. cooler on the unit. The transmission fluid bypasses the radiator completely.
alcusmc


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## alcusmc (Jun 5, 2006)

85 HRC W/454 Overheating

kg538,
Thank you for the reply. I have an Edlebrock Computer that controls the timing on the engine.. I will check the adjustment on the timing and see that it is correct. At present , I am running a 165 degree thermostat. I have changed it several times with various types. Even tried different size large washers with different holes in them..


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## JimE (Jun 5, 2006)

85 HRC W/454 Overheating

I have a 93 Winnebago Brave with a 454 and went nuts last summer trying to figure out the same problem.  After replacing everything and flushing the system and still having the same problem, I finally went to Alpin Haus in NY and they found the gauge was defective.


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## alcusmc (Jun 5, 2006)

85 HRC W/454 Overheating

JimE,
Thank you for the reply. I have checked the Radiator inlet when the engine was hot and the temp at the radiator is the same as the guage..

alcusmc


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## C Nash (Jun 5, 2006)

85 HRC W/454 Overheating

Have you replaced the water pump? Might also want to check the exhaust for restriction. make sure the ac condensor is clean. Does it only run this temp with AC on?  Ac could be running high pressure.


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## C Nash (Jun 5, 2006)

85 HRC W/454 Overheating

Also make sure the EGR system is operating.


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## C Nash (Jun 6, 2006)

85 HRC W/454 Overheating

More thoughts.  205 to 210 is not really hot for the 454. Was the outside temp the same as when it was running 195. Temp climing with speed incerase is an indication of timing problems.  have you checked the timing chain for wear.  Very simple to do. With dist cap off manually turn the engine clockwise to TDC on harmonic balancer then turn the engine counterwise until the rotor starts to move and read the degree on the balancer. Should be around two degree.


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## alcusmc (Jun 7, 2006)

85 HRC W/454 Overheating

C Nash,
Thank you for the information.. I have not checked the timing chain wear and I will do that and see what it is.. It did not occur to me that it would be worn at the low milage on the engine.. Even though the temp is not extreame @ 205=210 I could not understand what it just started running hotter that it had been for so many years.. The temp has climbed as high as 220 while driving.. I will also check the EGR Valve for proper operation.
Thank you again for the info.
alcusmc


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## C Nash (Jun 7, 2006)

85 HRC W/454 Overheating

alcusmc, I would not consider a crate engine at this point unless there are othr problems with the 454.  If it has been properly serviced it should have a lot of life left. 220 is not even to hot for this engine but, I understand your concern with the higher temp than it used to run.  Those years also were notorious for the centrificul advance in the distributer not working if you still have the HEI system. This can be repaired but you have to remove the dist and dissambly it.  The oil passage on the shaft would clog up.


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## Shadow (Jun 7, 2006)

85 HRC W/454 Overheating

Just a shot in the dark here. Maybe go back to the clutch fan. Just think they blow more air than the electric ones. May be worth a try at this point.


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## Krazeehorse (Jun 7, 2006)

85 HRC W/454 Overheating

New cap with the new radiator?


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## alcusmc (Jun 9, 2006)

85 HRC W/454 Overheating

Shadow,
I have changed back to the original fan clutch with a new GM fan clutch.. It was the same thing and I went back to the electric fans. They are designed for motorhomes and there are two of them on the radiator.. I also relocated the A/C condensor under the front of the unit and installed an electric fan on it.. There are no obstructions in front of the radiator..
Thank you,
alcusmc


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## bmwbob (Jun 13, 2006)

85 HRC W/454 Overheating

Here's another shot in the dark: How about your EXHAUST system?
I had a rig where the OEM catalytic converter started breaking down internally, and pieces of the platinum-embedded foam material went back into my muffler causing a loss in power, as well as higher operating temps.
One more try: Have you used any DuPont Zerex products in your cooling system? Our local parts place was out of Prestone, and I subbed the Zerex product.
Cost me the OEM radiator within less than 200 miles due to plugging, but I didn't attribute the problem to the Zerex at the time.
I replaced the radiator, and went along just fine for a couple of years (about another 70K miles) until, once again, no Prestone was available so I used Zerex radiator flush.
You guessed it: install ANOTHER new radiator! :-(
Let's not get a thread going about the relative merits of Prestone vs Zerex...that's not my intention. Just passing along personal experience.
As a parting shot, at your next oil change run a can of Gunk Engine Flush through it (per the instructions on the can), and, if you haven't already, consider going to synthetic oil.
Bob


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