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1998 GMC 5.7 coolant leak


redneck's Avatar
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05-10-03, 08:15 AM   #1  
redneck
1998 GMC 5.7 coolant leak

I have read on here in the past that these trucks have a problem with leaking coolant from the intake gasket!? Well, mine is leaking from the front of the block, just below the intake manifold. I have NEVER had a vehicle leak coolent from a bad intake gasket!? Anyone out there have this problem?--and if so, what is the cure? Just install a new gasket? It has 54,000 on it and has been leaking for about 10,000. Does not really lose much antifreeze, and seems to leak more just sitting in the driveway when cold! Thanks

 
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05-10-03, 09:55 AM   #2  
darrell McCoy
gasket will need to be replaced. For what it is worth, I would discuss the situation with a GMC dealer. See if there was a TSB concerning same. If so, perhaps you can work out some sort of deal on price with them.

 
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05-10-03, 10:03 AM   #3  
Joe_F
I agree. Get the bulletin # from Alldata.com and let me know what # it is. I will try to fax you a copy if you want.

 
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05-10-03, 12:31 PM   #4  
redneck
Well, the truck has been out of warrenty for some time and I do my own work--do not trust dealers. Interesting stuff on alldata--but nothing about collant leak or intake gasket. Well, off to the parts store for a gasket or two. Just thought someone out there may have all ready done this fix and had some pointers! I have never had to dig into this truck yet. Well, that is the advantage to owning more than one vechicle (one can be down--and you can still get to work to make a living) Even nicer when you do not owe anything on them!

 
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05-10-03, 07:21 PM   #5  
When you go to get your gasket(s), I'd recommend getting a new inlet water nipple, and an extracting tool. GM had a problem with those water nipples, and made replacements out of tougher metal..The tool should be available though most parts stores. I bought mine from a tool truck, and even there it only around $8.00. Just for info, in the last year, I've done maybe 20 intake gaskets on GM trucks ('95-'99 models) so for our shop, I'd call this a common problem...

 
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05-11-03, 10:28 AM   #6  
Redneck,
Have you never driven a GM vehicle before? LOL.

On any GM engine that has coolant running through the intake seems to have a problem sealing. I work for an Olds-Cad dealer, I would guess we do probably 2-3 dozen intakes on various engines a week. (8 man shop)
5.7 is lower on the list behind the 3.8,3.4,3.1,and 4.3.

Advice:
Don't use preformed end gaskets if they supply them-they will just push out (some-not all- aftermarket gasket have them)-use silicone.

Use brake cleaner sealing surfaces.

Don't use a cheap silicone- use one of the "ultra" brands. A little dab under and on top of the side gasket where it meets the end silicone will help eliminate coolant "creep".

Have somebody help you set the intake down. Try to drop it straight down. Moving back and forth will disrupt the integrity of the silicone.

Use medium strength threadlocker on all intake bolts. Go around twice on the final torquing to make sure all are at same the same rate.

Let it set an hour or two before filling with oil or coolant to allow silicone to set.(don't have this luxury at the dealership)

You will need a scan tool to time the distributor when you are done- no timing marks for a timing light. Timing is zeroed by PCM between crank sensor and camsensor within 1 degree or MIL will set.

Replace the pcv valve.

That's all I can think of right now.

 
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05-11-03, 11:31 AM   #7  
Joe_F
Good advice from FP.

 
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05-12-03, 05:04 AM   #8  
redneck
Gm is all I drive--first intake leak. 143k on 3.1--no leaks. Thanks for all the info--only thing I was not aware of was the timing deal--I do not have a scan tool--nor did I know it could be used for timing--I assume marking the orientation of the dist. before removal is not "close enough"? Maybe just to get it to a shop and have them set timing? thanks again.

 
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05-12-03, 06:01 AM   #9  
Joe_F
Sure you could do that. Or see if you can borrow an OBDII scanner from a buddy that might have one.

 
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05-12-03, 08:56 AM   #10  
redneck
Does anyone know how much $ for the scan tool? I may just buy one--I plan on keeping this a truck a long time.

 
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05-12-03, 09:03 AM   #11  
Joe_F
Redneck:

Ebay! There are always tons of those things on there and they go pretty cheap because they get "outdated" fairly quickly.

I got an OBDII compliant MPSI scanner from my friend for nothing...we swapped a couple of things in barter. In turn, I have to get the software for it and it ends at 1999. It shouldn't be that bad Works great!

 
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05-12-03, 02:11 PM   #12  
redneck
Ok, I looked at the OBD11 scanners and they say you can read codes and clear codes--how can you set the timing? Please educate me--I am still stuck in the 80's. In my '91 a scanner tool is a paperclip to read codes! Even looked through an owners manual for a new scanners, and nowhere in there does it say anything about checking the timing with it!

 
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05-12-03, 03:30 PM   #13  
Joe_F
A code reader just reads and clears codes, no real diagnostic capability there. You want a scanner.

 
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05-12-03, 07:56 PM   #14  
We use a Tech2 scan at work. Made by Vetronics for GM.The official GM scan tool for OBDII.
About $2500+software+support,etc... Only able to read GM vehicles.

On the GMC you look for a parameter called "cam retard offset"-turn distibutor while running, to 0 degrees and lock it down and you are done.

I do not know if a generic scanner will read the correct parameters. Some do,some don't. They don't all put in the same parameter readings for each vehicle. We can read GM codes with our Toyota scan tool and some parameters but CRO is not one of them(by the way Toyota scan tool is made by Vetronics also).

It may be easier to get it close and drive someplace to get it set.

 
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05-12-03, 08:15 PM   #15  
Didn't GM put marks on the actual distributor shaft on 5.7 and 4.3 engines? Put No.1 TDC, comptression. Pull the distibutor, and see if the rotor button isn't pointing to a small arrow(near the lip of the distributor) which also is aligned with a white line on the side of the shaft near the drive gear..?

 
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05-12-03, 08:26 PM   #16  
Distributors on 4.3 and 5.7 are interchangable.

Have a little 6 and a little 8 casted into the housing which you line up with a pointer on the intake depending if you have a v6 or v8.

But it may not get it close enough to keep the MIL off. About 1 in 20 that I do are close enough to keep it off. Some will trip the light as low as 1 degree off.

 
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05-13-03, 05:43 AM   #17  
redneck
Thanks to all, the coolant leak has stopped since the weather got warmer and I have been driving the truck more--it was not a bad leak to begin with--I am just picky. It also has a slight oil leak from the oil cooler lines--which was fixed once under warrenty.

 
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05-13-03, 06:34 AM   #18  
Joe_F
I agree with FP.

 
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