We noticed what i can only describe as sludge in our overflow tank and on
radiator cap on 1999 chevy venture. the "sludge" is brown in color and
clumpy. had the coolant system flushed around 120,000 miles. Now at a
little over 130,000 miles, "sludge" is back. im kinda thinking maybe oil or
trans fluid is leaking into coolant. anyone else ever had this problem or
any thoughts on fixing it? i forgot to mention van has 4.3l engine.
If you were loosing trans fluid could be the radiator/trans cooler. The
engine must be a 3.4 not 4.3, anyway if the sludge is only in the tank and
on the cap, this may be reisdue form the the flush and just clean what you
see and repalce the cap, if the radiator is blocked up this is a problelm,
was Dexcool reused or green put in? Sludging can be cause by degradation and
contamination of the Dex, if left in too long or the cap doesn't seal
Does it have the red colored Dex-Cool antifreeze in it? If it's not been
changed before 120,000 miles you may be experiencing issues from that. Even
after flushing it at 120,000 miles if you didn't clean the system with a
chemical flush you could still have remnants of the fubarred Dex-Cool in
Does the transmission or motor loose oil / fluid?
THis may have some merit. Given engine and age, GM had a lot of
problems with intake gaskets and if it has never been changed someone
may have put sealer in it. I have had the intake gaskets replaced
twice on my 2000 K3500 with a Vortec 350 free of charge in just over
38K miles total vehicle mileage. The last one a month ago and the time
before that almost 2 years ago. The latest change used a revised
gasket gasket and they told me that it should not cause any more
problems but they would make it right if it did. Some 4.3's were bad
about leaking and saw a gasket revision sometime before the 5.7's was.
No way! We "love" those intake manifold gasket jobs. Even
under warranty time, we make tons of money. I suppose there
may be some dealers that shy away from the job, but in our
shop, intake gaskets and head gasket jobs on these engines are
considered "pure gravy".
They've got better things to do then browse these forums.
Plus, they already spy on us anyways. The labour times
on intake gaskets has already been cut back....GM sees
the averages thru all the warranty work orders that are
Which is why I keep telling the guys in the shop to leave
themselves punched onto the warranty lines.....let em
rack up the time on those lines. Meanwhile you can
do the cp lines while you are running time on the
shiden_kai or cuda....
how long does it take to replace head gaskets on a 99 tahoe 5.7? Also, do I
replace the bolts...or are they reusable?
I'm thinking about doing this one over the holidays. I'm trying to decide
whether to try the intake gaskets first...or just dive right into the heads.
I'd really like to R&R the whole engine....but I can't do it until late next
year when my new workshop is finished.
Right no there is no evidence of oil in water or water in oil....just
coolant dripping all over...even with a 7 lb cap.
Unless you know for certain the head gaskets are leaking,
I would not bother with them. If you are just guessing, or
want to cover all the bases.....don't. We almost never
do head gaskets on those engines. But lots of intake
I bought this truck about 2 years ago and have put only about 20k miles on
it. (85k to 105k)
After having it about 3 months I noticed it was consuming coolant. So I
topped it off and connected my handy dandy pressure tester to it. I tested
the engine COLD so that any dripping fluid would not evaporate. It took
about 30 minutes of pumping from 10 to 15 lbs to generate a tad bit (like a
tear drop) of fluid leaking out the outer side of the passenger side head.
It was not much, but it was a leak. I really couldn't generate a leak I
could see when the engine was hot, so I let it go and added about a quart of
coolant mix every other month.
This summer, my water pump started dripping and by the time I got to
it...the pump was leaking pretty good. I replaced the pump and pressure
tested the system before I put it all back together and coolant was coming
out all over the manifold and dripping everywhere. I've driven it a few
times and there is no water in oil or oil in water that I can see. Last
weekend I rinsed the engine very well and topped the coolant. I am not
driving it. This weekend I'm going to bring it up to temperature and do my
best to see if it is just the manifold or if the heads are leaking too. I
also have a test bottle from Amsol to send in to test for glycol in the oil.
I would love for you to be right. As I said before, I'd enjoy pulling the
engine and re-building it to better than factory...but I can't do it until
late next year. I'm hoping it's just the manifold.
In the mean time, I'm driving my short bed regular cab c1500 cheyenne. I
bought it new for my wife in May of 93. It has a 4.3 that leaks coolant from
the front of the manifold where the intake, block and #1 cylinder all come
together. I love GM. These trucks are my fourth and fifth GMs. But I wish
they'd figure out how to get the gaskets right. They've only been making
that block for >40 years.
If you change the intake gaskets, you will probably get the new
design gaskets. I doubt that you will have any more problems
in the forseeable future using these gaskets.
As far as the head gasket leaking, it seems to me that it
may have "appeared" to be coming from the gasket when
in fact it's been the intake gasket all along. At this point,
unless you clean everything off, get a good light and a
flexible mirror and it leaks while you pressure test it, you
may not see anything.
Not that I'm aware of. It used to be the standard
practice with the Northstar engines, but GM doesn't
even recommend it for those engines anymore.
We certainly do not put the sealer into the 3.4 engines
in any attempt to prolong the life of the intake gasket.
We just replace it.
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