My 1994 K1500 5.7 is losing coolant. No external leaks and no smoke. I'm starting to think intake gaskets. I was under the impression this was only on the vortec engines and not the tbi ones but now I hear it is most of the mid 90's 5.7's. Anybody seen this on a TBI 5.7? I tried pressure test and it fails pretty quickly. Coolant is going somewhere it is not in the oil so I think its getting sucked into the intake stream thru intake gasket.
Losing coolant
- Thread starter rlast1
- Start date
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I have never seen that on that engine in 35 years as a professional technician. It is going somewhere, you just haven't found it yet. Head gaskets/cracked heads are very rare, but it can happen. Does the engine misfire on startup for 5-10 seconds after sitting for several hours or overnight?
I'm still betting on a slow external leak though. Sometimes, the leak is very high in the system, like at the top of the radiator, and will only leak coolant during a pressure test if the system is completely full. Otherwise, it just leaks the air pressure out.
Tom
mattbrat004
I'm Awesome
Here's what i did to find out. If you have time, i would suggest getting an oil analysis from blackstone labs, (28 dollars), this will tell you ppm of elements in your oil...you can learn alot about the condition of your engine this way. Anyways, I thought the same thing on mine, no noticeable leaks, but it turned out to be going into the engine oil. Or, you could goto a parts store and get some UV dye, put it in the coolant, and get it circulated. Then go back with a blacklight and check around the block, and the dipstick. Otherwise you could just go balls out and get an intake gasket set..at least you'd know the condition. Anyways, here's a pic of the test results for my truck.
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magimerlin
I'm Awesome
Check the hose fitting on the intake manifold that goes to the heater core. Also check the drain for the heater box that exits outta the freeway area.. if the heater core has a leak it'll drain outta that tube and you will not notice it..
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man you are talking about one of the simple things.if losing. coolant.hell if the over flow tank.makes you ad.you are losing some where..if water is not on the dip stick.or you do not see water.when you drain engine oil.milky milky brown or tan..check the plugs.pull out each one.you should see some difference on at least one.if not more.tan color.or white.
plugs tell the tale.most times.if the head is cracked or head gasket.look at the tip of your exhaust pipe.what color is it..hell pull the oxygen sensor.one or both.what color are they.white or some od color.crap is coming through your exhaust.time to pull the intake and heads.is any freeze plugs leaking.maybe one you can not see and a hot engine making it evaporate..i had a rusty one on my 305 tbi slow leaking..had it popped out and replaced.but if one is inside the trans bell housing.leaking.it could be mixing with a leaky.rear main seal.and looking like a small oil leak..the chevy 400 v8 engines were famous for blowing the gaskets and the cylinders..out.in between two cylinders.they were bored engine blocks.cheap head gaskets/factory they would start leaking and blow a grove.and ruin the blocks..a bored engine needs..great head gaskets..not cheap stuff..
plugs tell the tale.most times.if the head is cracked or head gasket.look at the tip of your exhaust pipe.what color is it..hell pull the oxygen sensor.one or both.what color are they.white or some od color.crap is coming through your exhaust.time to pull the intake and heads.is any freeze plugs leaking.maybe one you can not see and a hot engine making it evaporate..i had a rusty one on my 305 tbi slow leaking..had it popped out and replaced.but if one is inside the trans bell housing.leaking.it could be mixing with a leaky.rear main seal.and looking like a small oil leak..the chevy 400 v8 engines were famous for blowing the gaskets and the cylinders..out.in between two cylinders.they were bored engine blocks.cheap head gaskets/factory they would start leaking and blow a grove.and ruin the blocks..a bored engine needs..great head gaskets..not cheap stuff..
97Sierra4x4
Newbie
I am having a very similar problem. I am losing coolant at a consistent rate and I am not seeing it on the ground. I have noticed my tail pipe smoke a bit when I start it in the morning and noticed the oil color just turned to a tan color. have I caught it in time where I can just change the head gaskets or should I look into new heads/possible new motor?
If it is getting into the oil, it's probably from leaking intake gaskets, not head gaskets.
Tom
GarrettGmc
I'm Awesome
Just found this thread and figured I'd post here instead of making new one. So was in drive up atm and thankfully it's next door to Napa and one of the guys pointed out the truck was leaking, well pulled into parking lot and sure enough it was. Didn't think anything of it cause I have small leak from a hose but went in and grabbed some more coolant. By the time I came out there was a puddle. Limped it home ,only abt 5 mins, and popped open the hood, had coolant dripping right by water pump so figured it was leaking but after a sec I realized it was from the top of the intake manifold so today took it apart and im suprised there's no coolant leaking into the engine, front half of the gasket was cracked an/Or missing just built up oil sludge keeping it partially sealed.
tinfoil_hat
I'm Awesome
You are lucky it decided to leak where you could see it and not into the heads like they often do.
These engines are famous for lower intake gasket failure. Some people blame the factory coolant.
Go buy the Felpro gasket kit and a new tube of RTV. The kit has decent instructions in the box. You are also going to need a thorough flush because DexCool turns into brown mud in contact with the air.
These engines are famous for lower intake gasket failure. Some people blame the factory coolant.
Go buy the Felpro gasket kit and a new tube of RTV. The kit has decent instructions in the box. You are also going to need a thorough flush because DexCool turns into brown mud in contact with the air.
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