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Old 07-15-2018, 08:59 AM   #1
Join Date: Feb 2017
Posts: 53
88 Allegro, water pump/thermostat

My 88 Allegro is overheating. I'm pretty sure it needs either a new water pump or thermostat, but I figure its easier to just replace them both now since I don't know how old they are anyway. But I'm having troubles figuring out which parts to order so I can replace them with my brother's help.

Its a Chevy 454 7.4L on a P30 chassis. I went through AutoZone's site, and there is obviously no option to select a Tiffin Allegro in their search functions. Does anyone know how I can find the right part for this engine? I tried calling the local store to see if I could just give them the VIN and have them find the right part, but the guy had no idea what I was talking about or how to help me.

I did find the info for a 1988 P30 Van with a 7.4L V8, but it doesn't say if its in the 454 or not and I'm not sure how to make sure I'm getting the right part.

It also says its recommended to replace the fan clutch, so I obviously need to figure out that part as well. Additionally, I'm not sure which temp thermostat to get since they go from 160 to 195 degrees, and my temp gauge in my dash doesn't have any numbers on it, it just goes from C to H.

The closes thing I found on Autozone.com is: 1988 Chevrolet Truck P30 Van 7.4L 4BL OHV 8cyl. How do I determine if that is the same engine I've got in mine?
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Old 07-15-2018, 03:13 PM   #2
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Tiffin Owners Club
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Posts: 125
That is the same setup as yours. Some parts like brakes and suspension will tell you of it's for a motorhome or not but all water pumps should be the same. The 7.4l is the 454ci motor. On thermostat temperature it's really a preference thing. I'm not sure which temp is the best. You definitely don't want the coolest because it is hard on the motor if it never warms up.
1989 Tiffin Allegro 31 B
1965 Aristocrat Lo-Liner 16
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Old 07-15-2018, 03:19 PM   #3
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Location: Cincinnati
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7.4L is the same as the 454 cubic inch engine. I'd go with the 180 thermostat, it will allow the engine to quickly get up to operating temperature. No need to heat to 195 before coolant starts circulating.

Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI
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Old 07-16-2018, 12:00 PM   #4
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Posts: 578
can you say radiator??? After exhausting all avenues. It was a recoring of mine. New stat, water wetter, sealing up the front end to push all air coming through the grill into the radiator, new fan. The core was pretty corroded up. I had (4 rows) 3/8" tubes
they installed (4 rows) 5/8" tubes. problem solved.
1990 28' Georgie Boy, 454, 4bbl, Thorley Headers, Recurved Distributor, 8.75 mpg. RVM 76
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Old 07-17-2018, 07:06 AM   #5
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Thanks all. I was able to call Advance and talk to someone who actually knew what he was doing and find the right parts. Got them hopefully on the way.

Now I just need to get coolant. Anyone know how much coolant I'd need for the engine? I can't seem to find anything online that tells how much goes in the radiator and reservoir. I assume it would be easiest to get a 50/50 blend since we have to have everything delivered since we have no way of getting to a store, but I'm not sure if 3 gallons would be enough or if I should get 4.

I also found a mobile mechanic to come out and replace it all for me. My brother turned out to be not too much help and I need to get this done. He'll be here next Tuesday to do all the work, so hopefully it goes without any problems.
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Old 07-17-2018, 07:21 AM   #6
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My 93 held over 4 gallons of coolant , but I had drained the block as well. Now would be a good time to flush the system. I also replaced the fan clutch and recored the rad with a core with wider spaced tubes. Kept the 195 degree stat for the ECM to correctly operate the engine. No more overheating problems . Temp never goes over 210 now.
1993 Tiffin Allegro Bay 32'
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allegro, thermostat, water, water pump

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