The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1988 - 1998 GMT400 Chevy & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 10-16-2020, 10:13 PM   #1
rideblue00
Senior Member
 
rideblue00's Avatar
 
Join Date: Feb 2010
Location: Lambertville, MI
Posts: 1,852
98 K1500 Antifreeze in oil

So I have a 98 K1500 5.7. I have antifreeze in my oil and need ideas on tracking down why. No obvious signs. Im thinking that its the intake gasket or a head gasket. Im not sure how to definitively nail this down. If its a head gasket, I dont want to just do an intake gasket and then find out thats its the head gasket, and have to tear it down a second time. I work on my 66C20 all the time, but have not had to do much to this truck, its been great to me, 180k on it too! Thanks
rideblue00 is offline   Reply With Quote
Old 10-17-2020, 12:29 AM   #2
1967GTO
Registered User
 
Join Date: Nov 2017
Location: Riverside, Utah
Posts: 28
Re: 98 K1500 Antifreeze in oil

Intake gaskets are very common leaking points because of the plastic cracking and the pressure pushing the rubber out of place. Usually you can see it externally. I have seen a couple heads cracked on them. If you go to the head gaskets, make sure to have the heads checked for cracks.
1967GTO is offline   Reply With Quote
Old 10-17-2020, 08:17 AM   #3
Palf70Step
State of Confusion!

 
Palf70Step's Avatar
 
Join Date: Jul 2002
Location: Gulfport, MS USA
Posts: 46,575
Re: 98 K1500 Antifreeze in oil

Normally it's the back section of the intake over those back water ports is where it leaks. I do not think I have ever had in the last 40+ a small block chevy that didn't leak or start leaking there and have to be replace the intake gaskets.
__________________
Bill
1970 Chevy Custom/10 LWB Fleetside
2010 Toyota Tacoma PreRunner SR5 Double Cab - DD

Member of Louisiana Classic Truck Club (LCTC)

Bill's Gallery
Life isn't tied with a bow, but it's still a gift.
Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God!
Palf70Step is offline   Reply With Quote
Old 10-17-2020, 08:19 AM   #4
speedygonzales
Registered User
 
speedygonzales's Avatar
 
Join Date: Jan 2006
Location: Smithfield, VA
Posts: 1,501
Re: 98 K1500 Antifreeze in oil

It seems as though you are asking a question of how to figure out which is the problem. Unfortunately there is no method. A leakdown test (which pressurizes the cylinder) probably won't find it. That would tell you if the head gasket is leaking at the cylinder. Your leak most likely is between the oil galley and water jacket. So if it were the head gasket, it's not likely to be all the way to the cylinder. This problem is highly UNLIKELY. However, this test could make you feel better about the condition of the head gasket in other areas. If you had headers, I would say to take the extra step and change the head gasket just for comfort. But if you still have OEM exhaust manifolds, with bolts likely to break off, might want to skip this step. On the other hand, if you're removing the heads anyway, now is the time to fix the broken bolts. Can go either way on this one.

So that test is probably out.

The only other test you could do would be to pressurize the water system with a commonly available coolant pressure tester. They are available free of charge at most auto parts stores. As is the leakdown tester. However, while it will prove what you already know. You're not likely to figure out if it's one gasket from the other. Obviously if the intake is leaking coolant outside the engine, as mine always did. You would have been able to see it with out this tester. You could use dye to look for external leaks also.

You could try using a stethoscope to listen to the top of the plastic intake plenum while doing the coolant pressure test. If you hear gurgling there, it's got to be the intake gasket. If you don't hear anything, you don't know which it is.

As far as your likely candidate, the intake gaskets. As mentioned earlier, the OEM gaskets are plastic with embedded o-rings. They are garbage. Add to that fact that the bolt pattern of a Vortec intake has no center bolts and there is the recipe for disaster.

The only gaskets to use are the metal Fel-pro gaskets.
https://www.summitracing.com/parts/f...make/chevrolet
They last. If you have the original gaskets on this vehicle, I would be surprised they lasted this long. The OEM gaskets almost never make it that far.

A few words of caution.
While you can mark the distributor to put it back (near) where you took it out. You can do this and it may not set a CEL. No one ever gets it within ±2°. So the cam offset retard must be set with a live data scanner that has the capability for this step. So your code scanner is not going to cut it.

On the front passenger side of the intake is a quick connect coolant hose fitting. If you haven't already replaced it with a hose barb (I recommend). You are likely to have issues.

The vortec intake bolts are very VERY low torgue. DO NOT OVER TORQUE. When I do them, I do it in 3 steps not one or two. Remember that a torque wrench is most accurate in the middle of the scale. So if you are trying to use a wrench that is near the end of the scale, get a different torque wrench. One other thing, many people will tell you not to use the end gaskets for the intake manifold. I am one of them. I like Ultra-Black and follow the directions for letting it set for an hour. You can read the directions.

Look below the distributor to see that the oil pressure sending unit is leaking they all do. Now's a great time to change it with the distributor out. They are cheap. Just do it.

Many plastic connector safety clips are likely to break. The one on top of my CSFI unit broke years ago.

You aren't likely to like what you see under the plastic plenum that is on top of the aluminum intake if your EGR is still hooked up. It is going to be a black slimy mess. You're probably going to have issues getting the EGR supply tube off the front driver side of the intake manifold also.

Time to do the fuel pressure regulator while you have the plenum off. If you don't, you will regret it later.

Hopefully you switched to ethylene glycol coolant a long time ago. The OA "dexcool" is great for aluminum but not these engines. There is an entirely other set of problems with the early "Dexcool" that I'm not going into.

If you haven't already done hoses and belt in the last 4 or 5 years, plan on doing them as well since they are going to come off any way.
__________________
99 Z71 (98 body style)
Pride and joy
speedygonzales is offline   Reply With Quote
Old 10-20-2020, 08:56 PM   #5
Tom
driving is in my blood
 
Tom's Avatar
 
Join Date: Dec 1999
Location: Mesa AZ
Posts: 5,687
Re: 98 K1500 Antifreeze in oil

Pull the intake. If its not the intake you didn't waste anything because it has to come off for head gaskets anyways. So just pull it and see what's up.
__________________
-78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle.
-98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes.
-02 Suburban 4x4: leveled front
-CBR600F4i, CBR600RR, CBR1000RR, and standup skis
DISCLAIMER: I cant spell for the life of me.
Tom is offline   Reply With Quote
Old 10-21-2020, 09:00 AM   #6
rideblue00
Senior Member
 
rideblue00's Avatar
 
Join Date: Feb 2010
Location: Lambertville, MI
Posts: 1,852
Re: 98 K1500 Antifreeze in oil

Thanks guys, and thanks for all the extra info speedy.gonzales
rideblue00 is offline   Reply With Quote
Old 10-30-2020, 08:58 AM   #7
rideblue00
Senior Member
 
rideblue00's Avatar
 
Join Date: Feb 2010
Location: Lambertville, MI
Posts: 1,852
Re: 98 K1500 Antifreeze in oil

Well here it is. Front ports, both sides. At least its not the head gasket.
Attached Images
 
rideblue00 is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 04:27 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com