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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / February 2007Chevy Astro losing coolant
Hi Group, I'm looking for opinions and perhaps a little previous experience. I'm dealing with a 2000 Chevy Astro with the 4.3 litre V-6, automatic AWD and about 160K miles on her. Just the other day, I noticed that it had run low enough on coolant to stop providing heat to the cabin, and the temp climbed up to about 200 degrees (F). I refilled the radiator right away, but found the same situation about 400 miles later. Further investigation showed no visible leaks that I can find, and I think the oil may be emulsified. I have also noticed a rise in oil pressure - not much, but running around 50 psi at 65 MPH when typical was closer to 40 in the past. There may also be more steam in the exhaust that normal, but it is hard to tell for sure. I know that it is likely that a head gasket has failed but I'm looking (hoping) for other possibilities with this motor. Right now I've got the doghouse off and the shrouds off from around the fan. I was hoping for an easy way to get a compression test done, but those plugs are still quite elusive and buried. I can get there if needed. I was also hoping that there would be a way to pull the heads without pulling the motor, but it appears to be unlikely. Any advice on how others have dealt with this sort of problem in this vehicle would be greatly appreciated. TIA  SignatureTomO > Hi Group, I'm looking for opinions and perhaps a little previous > experience. [quoted text clipped - 16 lines] > Any advice on how others have dealt with this sort of problem in this > vehicle would be greatly appreciated. Sounds like a blown head gasket! First remove the dipstick. Look at the oil for whitish oil or try removing one of the valve cover caps, look at the inside of the cap. Is it foamy white stuff or dark? If it's foamy white stuff you will need to perform an engine block test to make sure their isn't a crack in the block If it turns out to be head gaskets, you can do the work yourself without removing the engine. .. To do the work yourself, you'll need a good service manual, a Haynes or, my favorite is Mitchell shop manuals. Haynes are more colorful, Mitchell manuals are spot-on. Chilton manuals I would touch with a ten foot insulated pole ie Chilton's are full of mistakes...not cool when your vehicle is sitting in your driveway in pieces... >> Hi Group, I'm looking for opinions and perhaps a little previous >> experience. [quoted text clipped - 18 lines] > > Sounds like a blown head gasket! [TomO] That's what I was thinking too. > First remove the dipstick. Look at the oil for whitish oil or try removing > one of the valve cover caps, look at the inside of the cap. Is it foamy > white stuff or dark? If it's foamy white stuff you will need to perform an > engine block test to make sure their isn't a crack in the block [TomO] Yeah, the oil appeared to be emulsified and somewhat thickened. It has more of a chocolate brown color than the black I expected. There is also the increased oil pressure. Not good signs. How do I do a block test? I haven't tried one of those before. > If it turns out to be head gaskets, you can do the work yourself without > removing the engine. .. [TomO] That seems a bit daunting in the Astro (minivan). Not sure I can really reach everything I need to. I'll give it a go if I'm encouraged enough though. > To do the work yourself, you'll need a good service manual, a Haynes or, > my favorite is Mitchell shop manuals. Haynes are more colorful, Mitchell > manuals are spot-on. Chilton manuals I would touch with a ten foot > insulated pole ie Chilton's are full of mistakes...not cool when your > vehicle is sitting in your driveway in pieces... [TomO] Thanks! I'll get a good book on this vehicle. I've built engines before so I kinda know what I'm getting into. It's more the engine placement in this vehicle that has me stymied at this point. > >> Hi Group, I'm looking for opinions and perhaps a little previous > >> experience. [quoted text clipped - 33 lines] > > How do I do a block test? I haven't tried one of those before. Using a engine block test kit! <snip> > Hi Group, I'm looking for opinions and perhaps a little previous > experience. [quoted text clipped - 21 lines] > -- > TomO I have a 99 astro ,4.3 that had the same problem. I thought it was just leaking from the weep hole on pump. The problem turned out to be the intake manifold gasket. The gasket only cost $30.00. The labor however, cost me $720.00. I hope you have better luck. ? wrote: > I have a 99 astro ,4.3 that had the same problem. I thought it was > just leaking from the weep hole on pump. The problem turned out to be > the intake manifold gasket. > The gasket only cost $30.00. The labor however, cost me $720.00. I > hope you have better luck. Oh no...my 98 Astro is doing the same thing... Yup, I was going to suggest the intake gaskets, which are more likely to fail. Signaturecorning_d3 http://www.automotiveforums.com > Yup, I was going to suggest the intake gaskets, which are more likely to > fail. [TomO] Cool. Is there a somewhat reliable method of finding the 'leak', or is it just a matter of removing parts and hoping that there is enough left of the original gasket to view the cause of the problem? I'd hate to replace the intake gasket, reassemble, and find that didn't do the trick. I'd also hate to pull the heads if that's not necessary. Advice and criticism always welcomed. SignatureTomO >> Yup, I was going to suggest the intake gaskets, which are more likely >> to fail. [quoted text clipped - 9 lines] > > Advice and criticism always welcomed. you cant always see the damage that lets coolant flow to oil from intake gaskets. if you have 'froth' in oil gallery its a fair bet tho if no outward leaks can be observed......................kjun >> Yup, I was going to suggest the intake gaskets, which are more likely to >> fail. > > [TomO] > Cool. Is there a somewhat reliable method of finding the 'leak', >> snip << Yes, TomO, there is. Borrow from Advance or Auto Zone or friend a pressure tester. It fastens onto radiator like a rad. cap. You can then hand pump it to raise the coolant pressure--if leak is external, you will see it. If it is internal, you should see it in the oil or coming from tailpipe when you next start it. If not external, *better* would be to remove plugs and spin it over AFTER you have pressurized it and seen the h2o level decrease right much--if getting into cylinders, the spinning over will shoot coolant out the affected spark plug(s) hole(s). If it comes out sp. plug holes, you still need to determine whether leak is due to intake or head gasket. HTH, s >>> Yup, I was going to suggest the intake gaskets, which are more likely to >>> fail. [quoted text clipped - 13 lines] > plug holes, you still need to determine whether leak is due to intake or > head gasket. HTH, s [TomO] Thanks, I understand that. I have already determined that coolant is getting into the oil and possibly into one or more cylinders. I was more wondering about best methods of determining whether the leak is manifold gaskets, head gaskets, cracked block, etc. Perhaps it's just visual inspection at this point? SignatureTomO The best bet is to remove the intake and inspect the gaskets. They're plastic with injection-molded rubber. You'll be able to tell if it is the intake gaskets leaking by inspecting the rubber. It can be squished(overtorque), cut, GONE.. You'll know right away by inspecting around the coolant passages in the gasket(the plastic usually breaks). If both gaskets look good, you've already got the intake out of the way to get to the heads. Make sure to change the oil AFTER changing whatever gasket has failed. Then change it again a week or so later to remove any residue left behind.. EDIT: It wouldn't hurt to use some blue threadlock on the intake bolts to prevent them from backing out and causing another leak.. Hey, it's happened to me. Signaturecorning_d3 http://www.automotiveforums.com If you have a head gasket leaking coolant into the cylinder(s), then more than likely, your coolant would be a nasty brown color, and pressure from compression should force coolant out of the radiator if you were to start it with the cap off(Only do this when the engine has cooled off!). At minimum you would see bubbles in the radiator. With the vehicle only being 7 years old, I doubt the head gaskets already need replacing, unless it's been severely overheated. That's not something I've seen much on GM engines. But intake gaskets are another story.. Signaturecorning_d3 http://www.automotiveforums.com > If you have a head gasket leaking coolant into the cylinder(s), then > more than likely, your coolant would be a nasty brown color, and [quoted text clipped - 5 lines] > something I've seen much on GM engines. But intake gaskets are another > story.. [TomO] I was thinking the same thing about compression showing up in the form of bubbles or extra turbulence. I do believe now that the coolant is getting into the oil. I hope to be able to remove the manifold this weekend and I'll keep my fingers crossed that I can find a break in the gaskets. I don't think I'll be able to pull the heads with the block still in this vehicle. Damned minivan, the engine is located directly below the dashboard! SignatureTomO They've got those 4.3's crammed in there, huh. I've had to do an intake gasket job on one.. It wasn't fun, but it wasn't that bad either. I'd hate to have to pull the heads... Signaturecorning_d3 http://www.automotiveforums.com > They've got those 4.3's crammed in there, huh. I've had to do an intake > gasket job on one.. It wasn't fun, but it wasn't that bad either. I'd > hate to have to pull the heads... Just out of passing interest, my neighbor started loosing coolant out of his 99 astro 4.3. Looking from below it was coming from the right rear of the engine up high somewhere. We pulled the doghouse to find the RH head gasket leaking water externally at the rear of the head. To make matters worse, it dribbles on his starter too... Astro engine access is a joke. Erik |
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