Oil in coolant, 1999 Chevy big block

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Originally Posted By: rationull
Originally Posted By: Chris142
Yes it will. Driver side of the radiator. Below the top hose are 2, 1/2 inch metal lines. Those are oil cooler lines and they go down to the oil filter pad on the block.


You're right, they're there. Never noticed that before. I suppose it's possible there's oil in the coolant as well. What would that look like? The oil level went down about 3/4 quart during the OCI, which I just attributed to burning given the engine's semi-high mileage.

Anything I can do to quickly test for this?
If there is oil in the cooling system there will be grey or black spooge everywhere inside and the hoses will be soft and shiney.
 
I've had relatives who had good luck with some kind of head gasket fix in a can. Not sure if it was Bar's but whatever it was seemed to work.

I'm not really too keen on taking a quick fix route for this truck, since we just bought it last year and it's more a tow vehicle than a beater. It's possible it might make some long trips at some point and I don't want to jeopardize its longevity. This idea did cross my mind though :)

If the leak's big then it's possible damage has already been done, regardless of the wear numbers on this particlar UOA. This was a short fill but I'm not sure how long the previous fill of oil was in it.

I haven't seen any spooge in the radiator, but I haven't taken the hoses off or anything.

Sounds like all I've got to decide is whether to fix it myself or take it somewhere to get it fixed more quickly. Fun.
 
Originally Posted By: Drew99GT
The 7.4L late model GM motors are in fact intake gasket eaters just like every other GM V-type engine from the mid 90s to about 2005.


x2

The Vortec 5.7 and 7.4L engines had terrible problems with the intake gaskets leaking coolant. It shouldn't be hard to find a shop that has experience replacing the gaskets, they have been a known problem for years. That said, once the problem is fixed that 454 should give you many more years of reliable service.

As for the oil consumption, 1/2 quart during the OCI isn't bad at all.
 
The 1999 and up 4.8s,5.3s and 6.0s also have intake gasket problems which are plastic also,but not a coolant leak.The intake gaskets blow out and suck in air causing a miss
 
Originally Posted By: rationull


Sounds like all I've got to decide is whether to fix it myself or take it somewhere to get it fixed more quickly. Fun.
Replacing the intake gaskets is a piece of cake. I have never had to discharge an AC system to change one.
 
Originally Posted By: Rob_Roy

As for the oil consumption, 1/2 quart during the OCI isn't bad at all.


Taking mileage into account it was really 3/4 quart in 1500 miles but I'm not worried about it. The drain plug gasket was a poor fit for this OCI so I really have no idea how much oil leaked out vs was burned.
 
Originally Posted By: Chris142
Replacing the intake gaskets is a piece of cake. I have never had to discharge an AC system to change one.


The coverage in the Chilton's manual is a little iffy. Are we talking like a 1 weekend day process? It doesn't seem like it should be too bad. A lot of little stuff tends to slow me down though; moving stuff out of the way, fasteners, etc. I try to be extra careful and just don't tend to work that quickly.
 
Oh, and this is kind of off topic I guess but, Chris142, since you seem to know a lot about this setup.. Is there a drain plug for the in-radiator oil cooler that I'm supposed to be draining when I do oil changes on this thing? The manual references draining the oil cooler if equipped, but I'm not sure if that's only in reference to an external oil cooler some of the engines might have (given the manual covers something like 5 engines).
 
Taking the intake manifold off isn't that bad. You may need a tool to remove the fuel lines...I can't remember.

Remove the acessories, fuel lines, vacuum lines, distributer, a bunch of bolts with 9/16 heads and the intake will lift off.

Clean the surfaces on the engine and the intake. Install the new gaskets with a spot of silicone in the corners and bolt it back together. Will have to retime the engine when your done.
 
Originally Posted By: Chris142
Will have to retime the engine when your done.



Is timing done by rotating the distributor as usual? wafrederick1 said above it's set by scan tool and not by timing light but if the scan tool is necessary only to measure the timing at idle then I've got that covered.
 
You set the distribitor with a scan tool.Hook up a scan tool going in the data stream looking for cam sensor retard and the spec is 0 degrees.The part in the distribitor does the firings of the fuel injectors.If you mark the distribitor before pulling,you will not have to go through this step.
 
I wish I would have had those write-ups when I did my '97 5.7. I used the factory shop manual, and it was flat out wrong in places. Especially about the air conditioner mounting bracket.

Since my punishment for not having the truck done was I had to drive my Z-28 everywhere, I didn't have much motivation to finish the truck. When I finally did, I got the distributor one gear tooth off (that's after carefully marking, and following instructions to the letter). I found it easier with my 5.7 to just to use the alternate procedure for #1 piston at Top Dead Center.
 
According to my Haynes manual, for the 7.4 you have to remove the upper intake manifold before removing the lower, unlike the 5.7's. Also, there are front and back seals that sit on the block wheras the 5.7's you have to lay a bead of silicone.

I have a similar issue on my 96 Tahoe but its an external leak, and I don't know/not sure if there is an internal leak as well. The dipsitck is not milkshakey and the oil cap doesn't have any milky deposits on it... I have a Blackstone kit that I'll get a sample from to be sure..

The first linked article in the above post by hertzer talks about brown "rust" on the oil filler cap. My truck has that, but so do alot of other cars I've owned including a 05 Grand Cherokee that has no coolant leak. I figured that it was normal oil vapor deposits on the cap.
 
My GF's alternate plans for a truck this weekend fell through, so I'm taking it to a shop tomorrow. I'm still a little tempted to just let it be driven for the weekend since it's on new oil and the coolant hasn't been falling quickly lately but I guess I'm not going to risk it.

The shop owner didn't seem to think the 454s had this problem as often as the 350s but he'll look for signs and do a compression check to verify first. (I'm getting pretty lazy, so I guess I'll let him do it).
 
Oh, he believed me about the coolant. I did not bring a copy of the UOA. The guy I talked to when I brought it in today seemed more familiar with that specific problem and said it's usually pretty obvious. I'm anxiously awaiting a call from them later today.
 
Just talked with the shop. They don't see the normal external evidence of intake gasket failure, don't detect any combustion residue in the coolant (so probably not the head gasket) and any cooling system leak that's present is not showing up on a pressure check. That, coupled with the fact that its coolant level hasn't dropped for a while leaves me shrugging. Maybe the coolant was left over from an earlier service? I don't have any UOA trending yet to make that kind of judgment.

Turned up a few O2 sensor codes that hadn't set the CEL, and a possible worn distributor gear causing out of spec cam retard (which sounds like a fun repair) which is helpful but not related to the coolant issue.

Unless anyone here has any better suggestions, I'm going to pick it up tomorrow morning, keep driving it like we normally do (not much) and sample again in 500 or 1000 miles to see what shows up.
 
Add some UV dye to the coolant. I bought a UV kit which was mainly for A/C, but had some dyes for other components along with the special glasses and a light. The UV dye does not last a long time so you need to keep looking every few days.
 
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