Coolant Leak

Tiny
FILMLESS
  • MEMBER
  • 1999 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 339,911 MILES
I have a 1999 Chevy Silverado 1500 3 door 4x4 (Z71) with 339,911 miles on it. The truck has developed a coolant leak which I believe may be related to the heater core. Coolant drips down from behind the firewall when viewing from the engine compartment. The location (standing at the front of the truck) is to the left of the engine, behind where the heater core would be located. Inside the truck there is NO visual signs of a leak. The AC and Heat both work. No interior smells (of coolant) or visual fogs, etc. That is normally associated with a heater core failure. Is there a connection in that location that could product this? Thanks.
Do you
have the same problem?
Yes
No
Saturday, August 6th, 2011 AT 8:31 PM

52 Replies

Tiny
CADIEMAN
  • MEMBER
This is a heater core your right but to be sure this guide will help us find it

https://www.2carpros.com/articles/car-is-leaking-coolant

Please run down this guide and report back.
Was this
answer
helpful?
Yes
No
+1
Saturday, August 6th, 2011 AT 8:55 PM
Tiny
FILMLESS
  • MEMBER
Any chance this could just be a connection considering the heat still works. At this point anyway.
Was this
answer
helpful?
Yes
No
-1
Saturday, August 6th, 2011 AT 9:03 PM
Tiny
WRENCHER1
  • MEMBER
You will need to inspect it a little more closely and determine exactly where the coolant is coming from. If it is coming out of the condensation drain, then yes, it could be a heater core but you also have a number of hoses, pipes and connectors in that area that could also be to blame.
Was this
answer
helpful?
Yes
No
Saturday, August 6th, 2011 AT 9:03 PM
Tiny
FILMLESS
  • MEMBER
Just crawled under the truck. Leak appears to be coming from between the firewall, i.E: the firewall has a seam, two pieces bolted together.
LOGICALLY this would indicate the leak is coming from the heater core area. Guess I will have to pull the dash and inspect the inside.
Thanks
Was this
answer
helpful?
Yes
No
Saturday, August 6th, 2011 AT 9:14 PM
Tiny
AQUEMINILOVE
  • MEMBER
  • 1999 CHEVROLET SILVERADO
Engine Cooling problem
1999 Chevy Silverado 6 cyl Front Wheel Drive Automatic 200K+ miles

Last week my truck was towed and now were having this issue.

There is water/coolant leaking from a hose with a rubber adapter/connector piece against the engine firewall area. It seems to me a hose should have been connected to the piece, but theres no sign of a hose anywhere. The adapter slips on and off the hose easily, therefore I assume the missing hose would have the same.

I also noted that the top hose closest to the coolant cap isnt connected to anything either, and it was running under the air filter box but it does not reach the adapter and doesnt seem like the same guage anyway.
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:20 PM (Merged)
Tiny
CEMENT HEAD
  • MEMBER
The hose you speak that is closest to the radiator cap is for your coolant reservoir the hose runs along the wheel well and into the bottom of reservoir. The other hose coming out on top of reservoir is yet another over flow which this hose does not connect to any thing. You may have had coolant come from that hose due to the angle the vehicle was towed. I would say your reservoir must have been full.
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:20 PM (Merged)
Tiny
AQUEMINILOVE
  • MEMBER
What about the hose by the firewall with the black adapter end? Is something supposed to be attached to it? Because thats where it is leaking from.

Is that where the heater core or water pump connects perhaps?
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:21 PM (Merged)
Tiny
SONOBOB
  • MEMBER
If I correctly understand your description, the hose at your firewall sounds like it is one of the two heater core hoses that attach to a pair of plastic firewall bushings/couplers that step down from one diameter to another. One of these cracked on my '99 Silverado 2500 a little less than a year ago. I remember having to use an AC/fuel line disconnect tool to get the broken hose-end coupler off the firewall coupler. I can't remember the details, but will take a look at my repair and if I can get a photo of it, I'll include that when I get back to you with some more info.

Like cement head wrote, the hose at your coolant cap is an overflow that just runs along your fender well with an open-end termination.
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:21 PM (Merged)
Tiny
JACKSHAFTOE
  • MEMBER
  • 1998 CHEVROLET SILVERADO
  • V8
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
Coolant leak at the back of the engine near the distributor. Cannot see any source, but slow drip underneath at the area where engine meets transmission. Truck runs fine. Overnight puddle about the size of a dinner plate. Water pump area is dry.
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:21 PM (Merged)
Tiny
ELECTRICLOTT
  • MEMBER
More than likely it is the intake gasket if it is leaking in the back. Could be a freeze plug too. Check around the intake by the distributor area first. Its not always obvious, and can sometimes be hard to see, but usually that is the culprit. I have seen many problems with the Intake gasket on these models as they are supposed to be reusable. I"m just a shade tree guy, but I've owned 3 of these and had to replace the intake gasket on all 3. Good luck.
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:21 PM (Merged)
Tiny
CHAS.
  • MEMBER
  • 1998 CHEVROLET SILVERADO
  • V8
  • 2WD
  • AUTOMATIC
  • 79,000 MILES
I AM LOSING MY COOLANT, DO NOT SEE ANY ON THE GROUND, WHAT IS HAPPENING?
THANK YOU FOR YOUR ANSWER.
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:21 PM (Merged)
Tiny
MASTERTECHTIM
  • MEMBER
The most common leak is the intake manifold gaskets leaking in the front or rear of the intake manifold, also water pumps are very common for leaking. Use a mirror to look at the weep hole under the water pump for leakage
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:21 PM (Merged)
Tiny
OBXAUTOMEDIC
  • EXPERT
Hi Chas,

When did you notice the lose of coolant and how much ruffly are you loosing?

How is the vehicle running?

Have you checked your oil to see if it over full, looks milky or frothy? I it has any of these it is most likely a blown head gasket or intake gasket. Also is there more steam or white smoke as some people call it, coming out the exhaust.

Post findings here in forum.

.
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:21 PM (Merged)
Tiny
DCS1998
  • MEMBER
  • 1998 CHEVROLET SILVERADO
Engine Performance problem
1998 Chevy Silverado V8 Two Wheel Drive Automatic 132K+ miles

This is the first of several questions that I will Prob. Ask of you over time about this truck.
First a little history. This truck started leaking coolant at the quick connect for the heater and has been hot before.
A year ago, it started losing coolant (found it coming out the tail pipe. Used some Bar's Leak (for head gaskets and such) and it stopped using coolant. A day after this long and drawn out deal of the Bar's Leak, engine started idling pretty high (2000-2500 and now 3000). I still drove it a little just had to ride the brake when in a 30mph zone.
Had a fuel pump quit and replaced that.

Now to the meat:
I had read (by you I think)about spraying TB cleaner around the intake to check for leaks. I did that, and the engine sped up. That means there is a leak, correct? It was on both sides from front to back. I figure it burnt up the o-ring looking gasket when it got hot.
I went today and got a complet set of gaskets for the intake (top and bottom).

Im getting 4 codes (btw thanks for everything about code readers, their a great thing to have around) P0300, P0300pendind, P0507 and P0507pending.

Do you think all this trouble (random mis fires and high idle) could be caused by bad gaskets? Or do I need to get the gaskets in place and plain on making other repairs also?
David
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:21 PM (Merged)
Tiny
2CEXPT
  • MEMBER
Try erasing the codes again

Do you think all this trouble (random mis fires and high idle) could be caused by bad gaskets? Its leaking vacuum and the xtra air is not being measured by the MAF sensor.

Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

A Random Misfire code usually indicates a vacuum leak or bad gas.
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:21 PM (Merged)
Tiny
DCS1998
  • MEMBER
Side question and statment:
You mentioned "bad gas".
My Father had a small engine repair guy tell him, "Dont use gasoline with 10% Ethanol in it! Weedeaters, chainsaws and lawnmowers aint made for it!"

Could the same be true for trucks and cars as old as mine? Could that have helped mess up my fuel pump and get the last life out of that o-ring lookin plentum gasket? Just wonderin.
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:21 PM (Merged)
Tiny
2CEXPT
  • MEMBER
Could the same be true for trucks and cars as old as mine? Could that have helped mess up my fuel pump and get the last life out of that o-ring lookin plentum gasket? Just wonderin. I don't think it wiil affect the fuel pump-I'm concern about the gasket you mentioned get that squared away and then we'll go from there.
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:21 PM (Merged)
Tiny
DCS1998
  • MEMBER
Ras Dude,
Im not quite finished removing the intake and all yet, but wondering if you have the torque values for the intake, plentum and TB handy?
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:21 PM (Merged)
Tiny
2CEXPT
  • MEMBER
What engine is this 5.0 or 5.7?
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:21 PM (Merged)
Tiny
DCS1998
  • MEMBER
5.0L (305cid)
Was this
answer
helpful?
Yes
No
Tuesday, July 7th, 2020 AT 1:21 PM (Merged)

Please login or register to post a reply.

Sponsored links