Last night drove to my RV parking lot and saw 2 leaky spots on the asphalt under the rv. Spot number one is in front of engine and spot number 2 is right under the torque converter.I have put a bucket to try to collect something which was a few drops of a red color liquid which my its look and smell looks like coolant.Radiator, and hoses are all dry. Seems that the leak could be in the front and go slowly to back of engine.Note that there is no leak if the engine is running and only does this when it cools down.Apparently there is a known problem on all Vortec engines doing exactly that, leak when cooling down and that the leak is the from part of the manifold intake gaskets.Anybody had this issue? Or any ideas?

Look closely from under the rig at the water pump vent hole. You may only see a small rust track.

The 5.7 Vortec were prone to leaking from the coolant passages between the lower intake manifold and the heads. Cause was reduced number of bolts that held the intake to the head (not the fact that it is DexCool). I had a small block so I'm familiar with them, I never got real familiar with the 454 since I didn't have one.The remedy was to replace the intake manifold gaskets and use an RTV called 'The Right Stuff' or 'The Good Stuff', I can't remember which. It is a black sealant in a pressurized can. Can be bought at Autozone/Oriellys and similar places.I had the leak on my '97 GMC. I had to replace a head at 207k mi and the above is what I used. My leak had never returned at 244k when I sold the truck.

Most likely it's the intake gasket leaking. Not a hard fix and it is a common issue. Put in the Felpro gaskets and torque down the bolts slowly and evenly. Do not over tighten use the torque spec and a torque wrench. I've done a lot of these. My own RV with the 454 Vortec went bad at 30K miles. Dave

Any idea how much time my Chevy dealership should be taking for such a job?Thanks

I've fixed 3 of these. They were all leaking on the right front corner of the intake gasket. (Passenger side). Fluids seek their own level. So the coolant level inside the radiator should be at the same level as the leaking area. They tend to leak when cooling down. I guess the heat expands and tightens everything up.A upper gasket kit used to be in the $100 range. The hard part of the job is pulling and getting the distributor back in the right spot. I could probably do one on a pickup in days time. A MH, I have no idea. I would think a shop could do it in a day but they always have scheduling problems and other things to work on. So I'd figure on at least 3 days in the shop.

7.4 Vortec coolant leak | Good Sam Community

C350amg
Explorer
Oct 08, 2013
Just got a quote for this today. Small garage says its leaking by the left head gasket right in from of engine on the passenger side. They quoted 6397$ to change both head gaskets and my fuel injectors (the injectors really leak that i know)

That's way too much , tomorrow am it's going back to my trusted chevy dealer for a second advice!
Argosy24
Explorer
Oct 08, 2013
That's the cost of an engine not head gaskets. Somebody didn't want the job, it's a motor home. And something got twisted around, the left head gasket is on the driver's side.
C350amg
Explorer
Oct 10, 2013
Got a second diagnostic today from my regular Chevy truck dealer and the story is the same. Head gasket needs to be changed. The one thing which I liked is although their hourly rate is much higher than the 1st place I went to the total cost is way down. 1200$ in time 300$ in parts + another 300 for cleaning and resurfacing the heads.

Anyhow I will use this time to change my leaky injectors at the same time and those in Canada are ridiculously priced (200$ minimum each). I have ordered Lucas replacement from Fiveomotorsport, anybody tried these injectors on a 7.4

Thanks
Captain_Obvious
Explorer
Oct 10, 2013
I have the same problem with my 454. I replaced the upper gasket and that didn't help. For now, I just buy coolant. Eventually I may try a leak stopping agent.
prism
Explorer
Oct 10, 2013
C350amg wrote:
Got a second diagnostic today from my regular Chevy truck dealer and the story is the same. Head gasket needs to be changed. The one thing which I liked is although their hourly rate is much higher than the 1st place I went to the total cost is way down. 1200$ in time 300$ in parts + another 300 for cleaning and resurfacing the heads.

Anyhow I will use this time to change my leaky injectors at the same time and those in Canada are ridiculously priced (200$ minimum each). I have ordered Lucas replacement from Fiveomotorsport, anybody tried these injectors on a 7.4

Thanks

the $300 to resurface heads is way way out of line
C350amg
Explorer
Oct 10, 2013
Captain Obvious wrote:
I have the same problem with my 454. I replaced the upper gasket and that didn't help. For now, I just buy coolant. Eventually I may try a leak stopping agent.

As in you have changed both head gasket and intake gasket and this have a leak?
C350amg
Explorer
Oct 10, 2013
C350amg wrote:
Captain Obvious wrote:
I have the same problem with my 454. I replaced the upper gasket and that didn't help. For now, I just buy coolant. Eventually I may try a leak stopping agent.

As in you have changed both head gasket and intake gasket and this have a leak?

That's 150$ per head with the cleaning...too expensive?

Thanks
prism
Explorer
Oct 10, 2013
C350amg wrote:
C350amg wrote:
Captain Obvious wrote:
I have the same problem with my 454. I replaced the upper gasket and that didn't help. For now, I just buy coolant. Eventually I may try a leak stopping agent.

As in you have changed both head gasket and intake gasket and this have a leak?

That's 150$ per head with the cleaning...too expensive?

Thanks

Ok.Tell me what they mean by cleaning? If they disassemble the heads and clean the valves and chambers etc and install new seals then that sounds ok.Just to resurface the head can be done totally assembled
no need to disassemble

Forum Discussion

7.4 Vortec coolant leak

About Motorhome Group

Related Content

Coolant leak

Coolant leak

Coolant leak

Coolant leak

5.7L Vortec vs. 5.3L Vortec