how can you tell the difference between blown head or intake gasket?

Asked by Feb 04, 2014 at 05:25 AM about the 1999 Chevrolet Suburban K1500 LT 4WD

Question type: Maintenance & Repair

coolant in oil, milky; runs really rough, no heat, runs hot

26 Answers

22,315

it's hard to as they have the same symptoms. However if your oil is milky then your motor is on borrowed time now anyways. After you take the intake off the heads are just 1 more step, so if your going to do the intake gasket just do the heads as well

11 people found this helpful.
11,805

1999 suburban. Does it still have the vortec 5.7?? They are known for bad heads. Tell tale sign of heads/head gasket is your coolant system pressuring up as compression pressure escapes from the cylinder into the coolant system.

6 people found this helpful.
22,315

i have never hear of bad heads on a 5.7 (small block chevy). Now the intake gaskets on the vortecs other hand if you let them get bad enough you can over heat to the point you warp them

9 people found this helpful.
195

if your oil is milky, you are getting water into the pan via the head gaskets and intake on this motor if one is gone both have to be replaced also check main bearings and rod bearings for scoring if you ran for any period of time, they also may have to be replaced if you ran to long

9 people found this helpful.
11,805

@Andrew The newer vortec heads '95 and up (w/ the MPFI system) had a weak head design. I've got 3 out of 4 '96-'98 350's with cracked heads right know!! The head gaskets go fairly often. I've only had one intake manifold gasket go? The TBI's though, I've never had a head issue, couple head gaskets but a crap load of intake manifold gaskets. The old sbc's seam to hold up pretty good.

5 people found this helpful.
11,805

Could be a cold weather thing up here in canada?

2 people found this helpful.
120

I have a crack in my intank on the top could it be cracked on the bottom to and putting water in the oil

12 people found this helpful.
11,805

Possibly. Depends on where the crack is, intake runner or coolant passage. It can also indicate that the manifold isn't tightened down square causing the gasket to leak. The manifold should be replaced.

3 people found this helpful.
1,090

I have a1998 5.7 vortec and water is getting in the exhaust pipes and the oil pan why?

109 people found this helpful.
350

I have a 1998 suburban w454 and it has a or sounds like a rod knock but my oil isn't milky so what should I do

35 people found this helpful.
250

water is coming out my exhaust pipe,and my oil top is milky, can this problem be fxed. I have a 97 lincoln town car, high mileage...

25 people found this helpful.
130

My car runs fine but has water in the oil and oil in the water. But the car RUns fine. No skip or hesitation. Runs warm when water gets low. 97 Chevy lumina 3.1 titer v6. Is head gasket blows or lower in tack bowed.

13 people found this helpful.
140

most of the time with a blown head gasket u will have oil and water mixed in the pan, and milky substance under the oil cap, along with excessive coolant system pressure which could rupture the radiator , however with lower intake seals leaking on 96-99 chevy 5.7 Vortec, you will normally have an external engine oil/coolant leak, and or mysterious coolant loss with no external leak, which means it is leaking into an intake port and goin into the engine and out the exhaust

8 people found this helpful.
140

if u already have milky oil, your motor is toast, or soon will be toast, it will need to be disassembled and checked for damage and remachined with new parts as needed, so start thinking of getting a replacement engine and who will do the work, or start looking for a new vehicle.

3 people found this helpful.
22,315

You've never experienced a lower intake gasket leak on a 5.7 vortec have you? There is almost no way for the coolant to get to the intake ports via the gasket. It almost always is a viable external coolant leak or more common leaks coolant into the crankcase.

1 people found this helpful.
140

OK Andrew i will take your comment at face value , but why do people have to answer with a smart attitude? Anyway, So As a matter of fact i have one leaking now, no external leak, no extreme coolant system pressure, but it is losing coolant.

2 people found this helpful.
140

i will be taking the intake off and replacing gaskets soon, i will know for sure then.

20

what if water in the oil but not milky pulled valve cover off both sides a little moist but not like a head gasket would do took the intake off same as the valve cover a little moister but does have water in oil but not milky never ran hot but once due to bad water pump

2 people found this helpful.

I have a 1998 chevy express just cracked 100k. coolant getting into oil. most of the loss comes over night or when engine is cooled down. No obvious signs of a normal headgasket issue that I am used too, again im am mainly a diesel mechanic but I am still familer with gas as well. no pressure building in cooling system from a headgasket issue im thinking intake gasket from all that you are saying. smells like coolant a little no external leaks.

140

Do u have a compression tester? How about a coolant system pressure tester? Performing A compression check and coolant system pressure test would give some strong clues, if compression is fine, then most likely an intake gasket issue, the coolant system pressure test would confirm it, and if u have a stethoscope and listen thru the spark plug holes u will probably hear it leaking. you can wear the stethoscope while pumping air into the radiator, I would also get a cheap leak detector kit, comes with flourescent green dye , some yellow glasses and a small flourescent light, add the dye to your cooling system a few hours before you check compression or pressure test the cooling system, gives the dye time to circulate, when i did my truck, i found hoses up front by the water pump were leaking, real easy to see the dye with the glasses and the light, Sounds like you could have leaky intake gaskets, good luck, check back with your findings :)

1 people found this helpful.
10

My local auto parts store rents a tool( they call it a block tester ) (30$ and then they refund it at Orileys,)that checks for combustion gas in the radiator it's a very simple machine consisting of a bulb to draw air from the radiator cap and a glass tube with a diffuser. By adding a specific chemical also available at the parts store for 10$ and drawing air through the radiator(cap off engine running) the chemical color tells if you have combustion gas in your coolant . As in head gasket,cracked head or cracked block.. if the chemical does not change colors it's possibly the intake gasket... I understand damage may have been done to the lower end while water is in your oil pan but if you do a double oil change after repairing the intake gasket it's still worth driving. Additional moisture left will evaporate and there are some pretty nifty hyperlubricants available that can keep things moving smoothly ..

1 people found this helpful.
10

J ...u r so right... I have a 95...losing coolant...not much...but I am having to top off my coolant/water about once every 2 weeks...I have no leaks...I installed new radiator...waterpump..hoses.heater core about 6 months ago...noticed water coming out the exhaust...not a lot but enough.....I just replaced timing chain a month ago...another way...start your engine...spray brake cleaner around your intake on both sides...if you notice a change in the idle... U got a leak...

1 people found this helpful.
10

Rebuild.....all the answers are pretty much right. I had a blown gasket in my nine 7 burban about 5 years back, did what chevy guys do rebuild-cooked- problem solved

1 people found this helpful.

I have a 1998 Chevy 1500 and have antifreeze running out towards the back of the engine. I think it's at bottom of the head but can't tell for sure. Any thoughts before I assume a head gasket?

140

Russ429 : when engine is cool, I would put an ounce of coolant dye in the cooling system, fill it to full, put cap back on, start and run for about 10 minutes so it can circulate throughout the cooling system, get the special yellow glasses and light (about 10$) then try and find a dark spot or wait until dark then go under your vehicle with light and glasses and look for the leak, it will show up as fluorescent. most likely u will have a hose leaking or even the manifold. report back with what u find,

J: I see it pour out from underneath the truck but I can't see it from above so well because of parts in the way. Also it doesn't pour out just because it warms up, it pours out when I get the rpm up. I'll look into the dye as well thanks for the input.

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