VT V6 Supercharged Mystery Overheating Problem

[Co-Pilot]

Co-Pilot

Hi Guys Hope this helps you. My supercharged VT had similar overheating problems it was easily fixed in my case. I found that the hose to the overflow tank had gone brittle and broken off just where the hose enters the overflow tank neck but just inside the overflow tank neck, this looked fine from the outside but was stuffed. This broken hose worked fine whilst water got hot and therefore expanded and emptied into the overflow tank. But when the water in the radiator cooled and therefore contracted and tried to suck coolant back from the overflow tank it just sucked air as the broken hose in the overflow tank neck was not immersed in the coolant fluid of the overflow tank - end result nothing to suck back and overheating due to low coolant level in radiator. I removed the overflow tank and got the old bits of hose out of it, reinstalled it, replaced the damaged hose and made sure that the replacement hose reached the bottom of the overflow tank. I made sure I cut the bottom end of the hose at a sharp angle (about 70degress) to stop the hose sucking on the bottom of the overflow tank which, if it did this would also not suck back coolant. This new hose worked a treat and I have had no problems since. P)

 

[brooom]

I'm going to dare say that your initial problem might be in the overflow, and the constant overheating is leading to other problems in your radiator (like little bubbles of air getting stuck in the tiny radiator tubes). When bubbles get stuck in radiator itself the radiator can't work efficiently, and needs more air than normal blowing through it to work. This would explain why it overheats at idle, but not on highways.

The same thing can be caused by the drive belt being a little bit loose, or the radiator fins being obscured. The loss of fluid without leaks may be as simple as the coolant is getting so hot it's simply evaporating when it hits the overflow. Either way you've still probably got air in your system, making things worse.

I'd suggest having a good look at the overflow and check for cracks or leaks, and it never hurts to check your belt tension and give it a tighten, and check your radiator's non-obscured anyway (and clean away any dirt, dust, small animals...). As for any air stuck in there, I'd recommend completely draining the system from the bottom hose *with* the radiator cap still on, so all the bubbles get sucked back out from the pressure, and then purging the radiator with a *clean* air compressor at no more than 75kpa from the top of the radiator (from the top hose is best, cap still on) to push the more stubborn bubbles out through the bottom. I recommend draining the block too, as if there's air that's found its way into a convenient corner it will stay there no matter how much fluid is flowing past.

When you re-fill the system, fill the radiator first, and then remove the top hose from the radiator side and pour coolant directly into the engine block this way.

When you bleed it, check a manual for the correct procedure, and be anal retentive about it. I'd say to bleed it the old way (with a funnel) too just to be sure, and rev the engine a few times once the fans have engaged to force any tiny bubbles out before finishing.

 

[Brett_jjj]

Hi Guys Hope this helps you. My supercharged VT had similar overheating problems it was easily fixed in my case. I found that the hose to the overflow tank had gone brittle and broken off just where the hose enters the overflow tank neck but just inside the overflow tank neck, this looked fine from the outside but was stuffed. This broken hose worked fine whilst water got hot and therefore expanded and emptied into the overflow tank. But when the water in the radiator cooled and therefore contracted and tried to suck coolant back from the overflow tank it just sucked air as the broken hose in the overflow tank neck was not immersed in the coolant fluid of the overflow tank - end result nothing to suck back and overheating due to low coolant level in radiator. I removed the overflow tank and got the old bits of hose out of it, reinstalled it, replaced the damaged hose and made sure that the replacement hose reached the bottom of the overflow tank. I made sure I cut the bottom end of the hose at a sharp angle (about 70degress) to stop the hose sucking on the bottom of the overflow tank which, if it did this would also not suck back coolant. This new hose worked a treat and I have had no problems since. P)

I also had this happen to my VY when I first got it. Someone had cut off the hose inside the bottle, it was only about an inch or two long from where it entered the sealing grommet in the bottle, so it couldnt even reach down to the coolant . . I ordered a new overflow hose and problem fixed, no more loss of coolant from the radiator.

 

[brooom]

By chance, I happened to fix a problem on my old man's Statesman today who had almost exactly the same problem:

- Coolant mysteriously disappearing
- Overheating when idle
- Running at higher than normal temp
- Creamy color to coolant in the reservoir, regular green in the radiator and engine block

What was making the car do this was the pressure valve between the reservoir and the engine block was gunked up and blocked. As the pressure built in the radiator, overflow was going into the reservoir alright, but nothing was coming back in, so the next pressure release would be just steam. More or less, it was pretty much just vapor on his coolant system, as nothing could get back in.

What caused this to happen (current theory) is he decided to try putting Stop-Leak in his system but put it in the reservoir rather than directly into the radiator, so the stuff started coagulating around the outside of the reservoir bottle and on the valve rather than inside the coolant system.

I just cleaned the valve off, scrubbed the bottle and re-installed it, putting some fresh coolant in it while I was there.

Might be what's happening with your car. Hope that helps.

 

[Shebang]

Thank you for the help guys.

I checked the overflow hose and it is in good condition not blocked or split. It is currently losing 1 litre of coolant per trip trip but still with no sign of coolant under the car anywhere and the coolant reservoir never seems to change its level, it is always full to the top. I am filling it via the radiator cap and bleeding before every trip.

I just have no idea where the coolant is going and neither do the mechanics. It passes pressure testing no problem, the oil is clean and they done chemical test to check head gasket which came back fine and no smoke or coolant coming from exhaust

No idea what to do :bang:

 

[The1]

are you getting oil in the coolant? even some pressure tests wont find intake gaskets as it's only while the engine cools that oil gets sucked into the coolant, Some of the coolant may also be going in the intake and burnt without any sign of it at the exhaust. Especially if you have the plastic intake gaskets i would be replacing them with the alloy type.

If you want to come up for a drive i can check all the sensors, tune etc, have tech2 and all the tuning gear.

 

[chargedvx6]

Thank you for the help guys.

I checked the overflow hose and it is in good condition not blocked or split. It is currently losing 1 litre of coolant per trip trip but still with no sign of coolant under the car anywhere and the coolant reservoir never seems to change its level, it is always full to the top. I am filling it via the radiator cap and bleeding before every trip.

I just have no idea where the coolant is going and neither do the mechanics. It passes pressure testing no problem, the oil is clean and they done chemical test to check head gasket which came back fine and no smoke or coolant coming from exhaust

No idea what to do :bang:

Intake manifold gaskets!!! Change them, that is all Inlet Manifold Gaskets - Mace Engineering Group

 

[Shebang]

The1, Thank you for the offer but I am a bit far away from Toowoomba. There does not seem to be any oil in the coolant, I believe they tested for that.

How much do you guys think a fair price would be to have a mechanic do the intake manifold gaskets? I am not mechanically minded enough to do them myself.

Cheers.

 

[Schwuppes]

should be around the $600 mark if you use the alloy type gasket (dont let them put the crappy plastic gasket on again)


Btw, your radiator fans are working, right?

 

[Shebang]

Yes fans come on as soon as the temp hits 96c, both of them, and then the temp falls IF the coolant level is good.

I will buy the alloy gaskets and supply them to make it cheaper.

Is it easy to replace the thermostat at the same time? Bear in mind it is the supercharged engine. If so, would I just buy the thermostat in the link below or do I need to buy a gasket seperately?

82 DEGREE THERMOSTAT TO SUIT ECOTEC, L67 & BUICK ENGINES - Mace Engineering Group

Thanks.