vintage air and overheating issue (LS engine)

[rodstored-72]

hi, I have '86 C10 swb with '13 5.3 gen iv DOD delete LS factory ecm and wiring harness, I installed a gen iv fact. replacement VA A.C. system. my problem is the engine gets too hot with the HCV closed. talking with V.A. and installed the "sometimes recommended" H-PIPE (recommended on "some LS and coyote engines). I am wondering if anyone else had to install a "H-pipe" to adjust for the HCV when closed?

[SilverGT3RS]

Originally Posted by rodstored-72

hi, I have '86 C10 swb with '13 5.3 gen iv DOD delete LS factory ecm and wiring harness, I installed a gen iv fact. replacement VA A.C. system. my problem is the engine gets too hot with the HCV closed. talking with V.A. and installed the "sometimes recommended" H-PIPE (recommended on "some LS and coyote engines). I am wondering if anyone else had to install a "H-pipe" to adjust for the HCV when closed?

I run an H pipe on my Classic Auto Air system for my 6.0 LQ9 I installed in my 67 C10. I did it because I converted the 6.0 to electric fans and it helped cool the truck in hot SC weather after reading about adding an H cross over.

[Joyridin]

I would think it is a good idea. I forget where i read how the coolant flows on an LS engine and you should never plug off the heater hoses. The heater coolant circuit passes over the thermostat to open it. So, the heater ports need a U-hose bypass to allow flow to open the thermostat and cool the engine.

[rodstored-72]

silver, thanks for the reply, did you use the H-pipe recommended?? or did you make your own? if bought, would you be able to list where purchased or the part no. ?

joyridin, thanks, I learned this as well after VA recommended their "fix". I guess it is not a very "common" issue - just ever so often.....

[rodstored-72]

well I installed the recommended H-pipe as directed by VA and..... no worky!! about 5 minutes after switching the AC on, the temp began to rise & I switched back to the heater when temp got to 240.....
so now I am really at a loss I will email VA again.. and see what Justin has to say again. this is very frustrating, I know this is a "custom" install (LS swap) but I don't understand why it seems to not be a regular issue & that VA could find a solution.... just my normal "luck"

[Joyridin]

Are you sure your fans are coming on when the A/C is engaged or the compressor kicks on? How old is the radiator?

This sounds like more of an issue than the H-pipe.

[rodstored-72]

the fans come on per the ECM fact. setting (203degrees) the radiator is brand new alum with fans CFM more than factory for the '13 engine. when the heater switched to heat the engine runs a cool 212-217 degrees, as soon as AC switched (HCV closes) the temp begins to rise (within 5min.). the heating issue began after (while) the VA A.C. install.
thanks

[LS short box]

So what are you running for engine thermostat? Stock? On my stock 20 Silverado with a 6.2 per the temp gauge it runs day in day out at 210 ish. But as soon as I turn on the AC the fans come on and stay on until the AC is off. On my 6.2 LS swapped 80 Camaro I used a 180 degree thermostat. Drilled some 1/8" holes in the flange to get some coolant flow even on startup. Fan set to go on at 205 and off at 195 via the ECM.
The other thing to consider as you are moving the heater hoses on and off you may have created a air block on/in the steam tube.

[kglowacky]

really a long shot but it happened to me via a bad mechanic. Fans running backwards.

[RustyPile]

New Radiator, but is it large enough?? The freon going through the condenser is very hot. Air passes through it first, then through the radiator.. If the ambient air temperature is already above 100 degrees, it is well over that exiting the condenser. Air that hot hitting a radiator that's already too small doesn't offer much cooling effect.

[mongocanfly]

My 6.0 swap has a 165deg stat in it.. fan1 kicks on at 175, fan2 kicks on at 185
I've never seen mine go over 185..and that's pulling some 10k loads..
You are correct on the H pipe...you don't need to impede the flow to the thermostat
or it will run hot
Does the H pipe switch to bypass when you turn on AC?

[rodstored-72]

well I had a shop look at it & it appears that the head gasket might be the issue. there is no indication of a leak into the rad. the engine stays cool until you switch the AC on or under a load (my luck!!) the shop feels the driver's gasket was not installed correctly - fairly easy to install upside down or backwards??? and would still "seal" right, but would block passages and keep from good flow??? so i guess now back to the engine guy for warr. work... aarrggg

[SilverGT3RS]

Originally Posted by rodstored-72

well I had a shop look at it & it appears that the head gasket might be the issue. there is no indication of a leak into the rad. the engine stays cool until you switch the AC on or under a load (my luck!!) the shop feels the driver's gasket was not installed correctly - fairly easy to install upside down or backwards??? and would still "seal" right, but would block passages and keep from good flow??? so i guess now back to the engine guy for warr. work... aarrggg

Definitely make sure you have the pump going the right direction and into the right port too.

I had that issue when I first installed the H pipe. When it was pumping the wrong direction my truck would overheat shortly after switching the AC on. Also, it took several tries to get all the air out of my system…the temps ran high until that was rectified too.

My 6.0 runs very cool, even idling in 100 degree weather the temp never goes over 190-200 degrees.

[rodstored-72]

thanks for the info. I believe the pump is right (water pump?) after trying the "H-pipe" the issue did not change. the engine guy indicated that the radiator flow test showed to be weak, so he is replacing gaskets to see if fixes????

[MalibuSSwagon]

I used this pressure bypass valve on my Vintage Air setup. It's basically an H-pipe except it's got a spring loaded valve in the middle. When the upstream heater valve is closed the coolant pressure pushes the valve open to bypass.

Four Seasons 74882 Pressure Bypass Open Heater Valve

[rodstored-72]

malibu, (and all).... thank you for the replies and suggestions. I took the truck to a "high end shop" and they did some diag on it , they determined that it was for sure mechanical. I took the truck to the engine builder and he agreed to revisit the engine. after his own diagnostics he agreed that it was mechanical, long story short it turned out to be a bad water pump (which was new from engine rebuild) replaced with a new auto store pump and it stays cool!!! now the truck runs at 190-200 with the AC on and in the latest temps ( phx AZ) of 105-112degrees! the history of the engine made it seem like it had to be a different issue than engine related - hence the run around with AC system, it was kinda a perfect storm of multiple things being installed and the temps still on the cooler side (mid 70's at time) so AC was not ran all time and not driving it real far.... this has been a very challenging build, but is starting to show signs of being worth it...