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Gmc 6.5 diesel heating

HEAVY386

Member
Joined
Mar 4, 2010
Messages
13
Location
Pleasant valley NY
Occupation
MOBILE EQUIPMENT MECHANIC
I have a 1999 gmc heating fine driving down the road or with idle up but let off at a light and heater drops off fast temp. gauge reads normal but no heat , tried bleeding several times still not much better any help ?
 

jrtraderny

Well-Known Member
Joined
Nov 26, 2006
Messages
236
Location
New York
Might be the heater core's starting to plug, also could be the water pump impellor is beginning to wear away from corrosion.
 

daman

Well-Known Member
Joined
Mar 22, 2010
Messages
237
Location
Bad Axe,MI
Occupation
Agriculture,Truck Driver,Mechanic
Try back flushing the heater core good. or is coolant level low??
 

FSERVICE

Senior Member
Joined
Apr 2, 2009
Messages
635
Location
indiana
you say tried bleeding. was the system opened for service/replace componet? that has 2 tstats could b one stuck open happened on mine. does it take a while to warm up?
 

barklee

Senior Member
Joined
Aug 4, 2009
Messages
903
Location
ohio
Bet your heater core is fried..... had a f-800 ford do the same thing. Couple weeks later the core cracked a leak.
 

smokey1

Well-Known Member
Joined
Jan 12, 2009
Messages
114
Location
West Bridgewater,MA.
Occupation
Builder/Owner
pull the hoses off the heater and hook together. the hoses should get real hot, this will eliminate a pluged heater core
 

surfer-joe

Senior Member
Joined
Mar 25, 2007
Messages
1,403
Location
Arizona
6.5s have real problems with coolant pumps. There is a replacement that works better and lasts longer. Check with your dealer. You may also have a problem with temp regulator, or with heater core.

6.5 is not a bad engine, properly maintained and set up. (I have two) Both of mine have improved turbos, performance chips, many mods inside the engine itself, and will run on nearly anything you can put in the fuel tank. I run B99 often, but also #2, or #1 if it gets real cold. No additives. Both units also exhaust via 4" tubing and freeflow muffler. Newer one has a cat off an 08 Duramax, just for visual effect at emissions test station.

Last but not least, get online with the 6.5 diesel forum. http://www.sixfiveturbodiesel.com/ There you will find many answers to 6.5 problems, and the vehicles they are installed in.

Good Luck!
 
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