Missing Coolant????????? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Johnny Merder · 03-04-2013, 08:08 AM

I have a 2005 GMC crew cab 2wd with 5.3, coolant is being consumed about a quart a week. i have checked all the usaual deals, no visible exteriaor leak, no smoke or smell from exhaust, no wet passenger floor. I did pressure test system and it wouldnt hold pressure, it went from 15psi down to 5psi in 20 min. Any ideas?

LT1 Burb · 03-04-2013, 10:12 AM

Head gasket, my yukon lost quarts over the years also but wasn't consistent.It would come and go but never caused any problems.

**truckdude239** · 03-04-2013, 12:43 PM

Check the waterpump before condemning the motor ifthewaterpump is leaking it has time to burn off before showinga leak look forthe discolor of dried coolant

Justin87 · 03-04-2013, 02:39 PM

The water pump should have a weep hole on the bottom which you should be able to see leaking or signs of it leaking if the water pump is bad.

bighaas79 · 03-04-2013, 06:35 PM

Quote:

Originally Posted by truckdude239

Check the waterpump before condemning the motor ifthewaterpump is leaking it has time to burn off before showinga leak look forthe discolor of dried coolant

I agree I have replaced dozens of water pump gaskets that the coolant would dry up off the front of the block from the heat of the engine, and not really leave a trace of leakage. Best way I have found is to get it up to op. temp. and pressurize the system, and watch the gasket area closely.

**Boog** · 03-04-2013, 09:38 PM

double click

**Boog** · 03-04-2013, 09:47 PM

Agree with bighaas. Water pump gaskets are prone to leak at times and dry before reaching the ground. Slow leakers but will eventually get worse. I just replaced the pump on my 2000 with 156,000 miles. Gaskets were leaking but then the bearing in the pump was going out also. Nothing from the weep hole yet however.

Johnny Merder · 03-05-2013, 09:59 AM

I pulled all the plugs out last night and used borescope to inspect cylinders, everything looked great. I pressurized the system and it wont hold pressure, but I cannot find an external leak.

**Boog** · 03-05-2013, 08:20 PM

Check to see that the motor oil and tranny fluids are the right color and not overfull?

Johnny Merder · 03-06-2013, 08:16 AM

I wish it was that easy to figure out, both the engine oil and trans fluiod are the correct color and level. I think I will pull the intake this weekend.

bighaas79 · 03-06-2013, 01:59 PM

Intake has no coolant going though it, not understanding this as your next step?

**Boog** · 03-06-2013, 08:28 PM

That's right. There is no coolant running through that intake manifold. The source of your coolant loss will be found elsewhere.

Johnny Merder · 03-11-2013, 09:36 AM

Well, after pulling the intake I couldnt find any place the front TB passage was leaking into the runner. I went over everything with a fine tooth comb, my local dealer had mentioned that they had a couple that were leaking into the runner from the TB passage, but mine wasn't. Back to the drawing board......

oldno7 · 03-18-2013, 08:07 PM

i would check where lower hose connects to radiator you could have small holes in the radiator there and its leaking only under pressure while driving

69gmcc10 · 03-20-2013, 01:29 PM

Did you check the water pump gaskets like truckdude239, justin87 and bigass79 suggested???!!!!! They are very prone to leaking on these trucks. My coolant was pulling a Houdini as well and the problem was the water pump gaskets.

03-04-2013, 08:08 AM	#1
Johnny Merder Registered User Join Date: Jun 2011 Location: Jasper, In Posts: 109	Missing Coolant????????? I have a 2005 GMC crew cab 2wd with 5.3, coolant is being consumed about a quart a week. i have checked all the usaual deals, no visible exteriaor leak, no smoke or smell from exhaust, no wet passenger floor. I did pressure test system and it wouldnt hold pressure, it went from 15psi down to 5psi in 20 min. Any ideas?

03-04-2013, 10:12 AM	#2
LT1 Burb Registered User Join Date: Sep 2010 Location: Winchester Oregon, formerly Vancouver BC Posts: 2,949	Re: Missing Coolant????????? Head gasket, my yukon lost quarts over the years also but wasn't consistent.It would come and go but never caused any problems.

03-04-2013, 12:43 PM	#3
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,237	Re: Missing Coolant????????? Check the waterpump before condemning the motor ifthewaterpump is leaking it has time to burn off before showinga leak look forthe discolor of dried coolant __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

03-04-2013, 02:39 PM	#4
Justin87 Registered User Join Date: Jun 2009 Location: Lawson Mo Posts: 147	Re: Missing Coolant????????? The water pump should have a weep hole on the bottom which you should be able to see leaking or signs of it leaking if the water pump is bad. __________________ 2006 Silverado 2500 HD

03-04-2013, 09:38 PM	#6
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,453	Re: Missing Coolant????????? double click __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross Last edited by Boog; 03-04-2013 at 09:48 PM.

03-04-2013, 09:47 PM	#7
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,453	Re: Missing Coolant????????? Agree with bighaas. Water pump gaskets are prone to leak at times and dry before reaching the ground. Slow leakers but will eventually get worse. I just replaced the pump on my 2000 with 156,000 miles. Gaskets were leaking but then the bearing in the pump was going out also. Nothing from the weep hole yet however. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

03-05-2013, 09:59 AM	#8
Johnny Merder Registered User Join Date: Jun 2011 Location: Jasper, In Posts: 109	Re: Missing Coolant????????? I pulled all the plugs out last night and used borescope to inspect cylinders, everything looked great. I pressurized the system and it wont hold pressure, but I cannot find an external leak.

03-05-2013, 08:20 PM	#9
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,453	Re: Missing Coolant????????? Check to see that the motor oil and tranny fluids are the right color and not overfull? __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

03-06-2013, 08:16 AM	#10
Johnny Merder Registered User Join Date: Jun 2011 Location: Jasper, In Posts: 109	Re: Missing Coolant????????? I wish it was that easy to figure out, both the engine oil and trans fluiod are the correct color and level. I think I will pull the intake this weekend.

03-06-2013, 01:59 PM	#11
bighaas79 Registered User Join Date: Nov 2008 Location: manly iowa Posts: 390	Re: Missing Coolant????????? Intake has no coolant going though it, not understanding this as your next step?

03-06-2013, 08:28 PM	#12
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,453	Re: Missing Coolant????????? That's right. There is no coolant running through that intake manifold. The source of your coolant loss will be found elsewhere. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

03-11-2013, 09:36 AM	#13
Johnny Merder Registered User Join Date: Jun 2011 Location: Jasper, In Posts: 109	Re: Missing Coolant????????? Well, after pulling the intake I couldnt find any place the front TB passage was leaking into the runner. I went over everything with a fine tooth comb, my local dealer had mentioned that they had a couple that were leaking into the runner from the TB passage, but mine wasn't. Back to the drawing board......

03-18-2013, 08:07 PM	#14
oldno7 Registered User Join Date: Jan 2007 Location: Ill. Posts: 584	Re: Missing Coolant????????? i would check where lower hose connects to radiator you could have small holes in the radiator there and its leaking only under pressure while driving __________________ Hi everyone, It's nice to know there's other people just as crazy about these old trucks as I am. oldno7

03-20-2013, 01:29 PM	#15
69gmcc10 Registered User Join Date: May 2011 Location: Missoula, MT Posts: 934	Re: Missing Coolant????????? Did you check the water pump gaskets like truckdude239, justin87 and bigass79 suggested???!!!!! They are very prone to leaking on these trucks. My coolant was pulling a Houdini as well and the problem was the water pump gaskets. __________________ 69 GMC C10 build thread- http://67-72chevytrucks.com/vboard/s...d.php?t=501676 03 Silverado build thread-http://67-72chevytrucks.com/vboard/s...d.php?t=591582



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