My daughter's 1997 Blazer (4 DR, 4WD) just started showing coolant in the engine oil. We changed the oil and it was 2 QTS overfull. I changed the oil in this darn thing less than a month ago and it was fine then, but the oil is loaded with coolant now. Nicely mocha colored, so it's Dex-Cool in there for sure. I'm not sure whether it's an intake manifold leak or a head gasket, but logic tells me the intake manifold is unlikely to leak this much this fast. I can do a compression test and see if it tells me anything, and my bet is that it's a head gasket.

Seems like the most logical thing to do if I want to keep this vehicle (or get any money for it on a trade, which is what I'll probably do) is to pull off everything and replace both head and intake manifold gaskets.

With the holidays coming up, I'll have a few days off when I could do work - but although I've done plenty of motor work including complete rebuilds and head gaskets on older cars (60's and 70's) I haven't had to do a head gasket on anything in the past 20 years. (Although I replaced the intake mainfold gaskets on an Audi V6 last spring.)

There's plenty of plumbing on top of that 4.3, and not a lot of extra room to work. My questions:

1) How practical is it to do the head gaskets on this car with the motor in place? Is it better to pull the motor?
2) How many hours is it supposed to take to replace the head gaskets? Anyone who's BTDT can probably give me a good idea.
3) How much of a total pain in the *** is this? It just looks like there's an incredible amount of electronics and such.

If I could do this in two full days (plus a day for a machine shop to check the heads and intake manifold) I'd probably do it.

I do have the alternative of changing the oil, running it to the nearest auto auction and waving goodbye for whatever I can get.

Feedback and BTDT comments are welcomed.

 

well, u stated the hard part, all the electrical. make sure u label all the connectors before u remove anything. i had a friend out here just rebuild his 4.3 in his 97. didnt label anything.

everything is really tight, and if u want to be able to get more room, pull the front clip. it isnt that hard. but it opens up the area nicely

but before u start it. do the comp test. see if it is a headgasket. if it is just a intake gasket, job gets simple. remove the rad cap and fire up the engine. see if the coolant is getting pushed out or bubbling alot. if so, there is a leak into the combustion chamber. if thats so the coolant is getting into the oil when the truck isnt running. unless it is a leak from the oil to the coolant passage, but i never see that.

 

First off is the engine missing or running poorly? If you are getting coolant into the combustion chamber it is bound to have some kind of sign of the coolant being burned (smoking, missing,running rough...etc.). It is very common for these to leak coolant internally and externally from a failed intake gasket, and very rarely do the head gaskets fail (unless they are ran very hot). It sounds to me like you have a blown intake gasket and I would be comfortable taking the intake off and checking it ...if it's obvious that the gasket blew I would not take the heads off.....just replace the intake gaskets and reassemble it, but make sure you flush that intermix out thoroughly before you run it again. I have seen main bearing failure as a result of running these with intermixed coolant and oil. If you do have a head gasket problem, you definitely want to change them IN-CAR. It is no easy task to remove these engines...you have to lift the body up about 4 inches off of the frame to do it. I would suggest running a complete compression test first, but I'm almost positive you have a failed intake gasket. To answer your question about time...it pays about 10 hours to replace both head gaskets,......and it pays about 22 hours to r&r the short-block (engine with transfer of cylinder heads).

 

Yarf!! Thanks for the info about head vs. engine removal.

The engine runs perfectly, and there are no trouble codes. I just checked the coolant and it was at least one quart low in the radiator, plus needing another 1-2 qts. in the burp tank.

I'm also thinking intake manifold. My logic goes like this:

- The oil had about 2 quarts of coolant in it when changed. (It was @2 qts. overfull)
- I've driven it for two days after the oil change with no visible trace of coolant showing up in the oil, however, this was BEFORE I topped off the coolant today.
- The intake manifold is the highest point of the motor that has coolant running through it. If the coolant level were low, it should keep leaking through a bad head gasket - but there might o be less coolant circulating through the intake manifold, therefore less coolant would be available in the top part of the motor to leak.
- I'm going to watch the oil carefully now that I have the coolant topped off again. If discoloration shows up quickly, I think that points more strongly to intake manifold.

Does that line of reasoning make sense?

 

intake manifold gasket...maybe 4 or 5 hours...be sure to flush all that crap out of your engine...dont just do a normal oil change.

 

if it came down to doing a head gasket, i'd try running bars leak through it first. although some would say thats half-assed, that stuff works miracles and ive used it more than once and had it make a permanent repair for me.

 

If yo udecide to do this.....

You need a manual like a Chiltons or Haynes. They can guide you pretty good.

Things to remember:
Head gaskets, (do both) valve cover gaskets, intake manifold gasket, ft lbs torque wrench, inch lbs torque wrench, piston ring compressor.... why not install new rings?.....

Coolant in oil is a bad thing. Change the oil/filter when you're -DONE- with the head job.. Have purchased an oil change flush and pour it in. Run the engine for a bit and change the oil/filter.

 

I'm more and more inclined to think it's intake manifold.

I'll be driving the car today and tomorrow, and I'll see if coolant shows up now that it's topped off. When the motor is cold I'll try a compression test if I get real inspired.

I have the factory service manual and a Chilton's - but no way would I mess with the rings, because that would require a acomplete motor removal and disassenmbly. No point in that.

 

I'LL SECOND THAT!!!!!!!

 

I have a problem to. My truck was running low on antifreeze, so I had to fill up every couple of days. Then I noticed my temp gauge moving from cold to hot then I put more antifreeze in and it stop. So I noticed a leak in my upper radiator hose erplaced that then I noticed a big leak on the back of my block. all my hoses are fine and I saw my water pump leaking. I replaced that and it was still leaking so I took to Firestone and they said it look like intake leaking. They told me to take to the dealership. About what is the range to get that done I work at advance so I can get the part I just wanna know what the lobor is?