$1500, Still Overheating!

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4 years 7 months ago - 4 years 7 months ago #134761 by PatriotSpade
$1500, Still Overheating! was created by PatriotSpade
2001 Infiniti QX4 4WD
3.5L V6 (VQ35DE) 190k miles
United States

Things which have been replaced:
Thermostat, Water Control Valve (second thermostat), Water Pump, Radiator Cap

Tests ran:
Chemical Block, Cooling System Pressure, Compression, Leak-Down

I bought the vehicle after inspecting it personally and finding no major issues outside of a coil pack issue. A couple days later the vehicle overheats after being on the interstate for 2 miles. Vehicle will idle without overheating, and can be driven less than 35 mph without overheating. I replaced the main thermostat, did not resolve the problem. I was afraid I did not bleed the system correctly, took it to a local mechanic. No change after bleeding cooling system, so he did a block test which "failed" but he was perplexed due to no coolant leaking and no mixture of oil/coolant. Suggested I take it to a Nissan specialty shop. The specialty shop ran chemical block test and vehicle passed. The specialty shop stated that after bleeding cooling system using Varajet system, the vehicle would get approximately 5 miles interstate and overheat. They manually bled the system and found major air pockets. They then ran coolant system pressure test and compression test, both passing with flying colors. We replaced the water pump, did not fix the issue. Decided to replace the water control valve (second thermostat for the block). The water control valve sits underneath the intake manifold. They found dog food underneath the upper and lower intake manifolds. It was then obvious the vehicle had been sitting for a while. They also found a leak at the block water outlet (see attached picture). They cleaned that mess up and replaced the block water outlet gasket, water control valve, and bypass pipe gaskets. Still overheating. The specialty shop is perplexed.

EDIT: Also adding pictures of the cooling circuit for reference since it's an odd system.






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Last edit: 4 years 7 months ago by PatriotSpade.

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4 years 7 months ago #134771 by cap269
Replied by cap269 on topic $1500, Still Overheating!
Ok, let's start with the basics. How is the fan clutch? Blades on the cooling fan all ok? Radiator shroud(s) in place? What happens if you collect some of the oil and drip it onto a very hot surface? Does it sizzle or just roll around and smoke? Next, since the vehicle was sitting "for a while" there could be foreign material or corrosion plugging the radiator, or the radiator could have rotted inside. There could be corrosion or foreign material inside the engine restricting flow, maybe even just in one area causing an isolated hot spot. Why was the vehicle parked so long? Maybe this is an old problem that caused it to be parked in the first place (in this case you have no history of cause and previous repair attempts).

Current vehicles:
'88 Toyota Truck 2.4L I4 (22RE)
'05 Hyundai Accent, 1.6L I4
'06 Volvo S60 2.5T I5

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Too many to list

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4 years 7 months ago #134777 by PatriotSpade
Replied by PatriotSpade on topic $1500, Still Overheating!
✔ Fan Clutch
✔ Fan Blades
✔ Fan Shroud

There was no antifreeze in the oil or visa versa according to the shop. Old oil has been disposed of so cannot be tested further.

Radiator is clear, and I actually flushed it myself when changing the thermostat before ever taking it anywhere. The old antifreeze looked good and there was no residue in the radiator. The flush was fairly clean, and water flowed very well. I tested it by plugging the lower hose port, filling it with water, and unplugging the port. With gravity only, water flowed out of the lower port very well.

I do not know why the car was parked and do not have contact with the previous owner. Honestly, the car being parked is only speculation based on the evidence of a rodent/animal making itself a home under the intake manifold. However, I've heard stories of techs finding the same thing in a car with 5,000 miles on it, so take that for what it's worth.

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4 years 7 months ago #134784 by college man
Replied by college man on topic $1500, Still Overheating!
When you drive the car is there good hot heat?

Believe it or not Iam trying to help you.

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Mobil1 New Jersey highway tested everyday.

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4 years 7 months ago - 4 years 7 months ago #134785 by PatriotSpade
Replied by PatriotSpade on topic $1500, Still Overheating!

college man wrote: When you drive the car is there good hot heat?


Heat is great at idle and up until the vehicle begins to overheat. As soon as the temperature starts climbing the heat plummets from scalding to lukewarm. Keep in mind it will idle and can be driven less than 35 mph all day long. It only overheats at higher speeds than 35 mph.
Last edit: 4 years 7 months ago by PatriotSpade.

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4 years 7 months ago #134790 by college man
Replied by college man on topic $1500, Still Overheating!
I would try and bleed the system again following this procedure.
If you don't have the spill free funnel put a pan under the car to
catch any spillage. The cooling fan must cycle.Follow the video on
how to bleed a cooling system.

www.ericthecarguy.com/faq/what-to-do-when-your-engine-overheats

Believe it or not Iam trying to help you.

Proud to be Eric The Car Guy Certified.

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Mobil1 New Jersey highway tested everyday.

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4 years 7 months ago #134793 by ukrkoz
Replied by ukrkoz on topic $1500, Still Overheating!
I bet you have exhaust leak into the coolant causing overheat. That it happens past 35 mph tells me it's a pinhole that gets worse as exhaust/combustion pressure increases.
I donno, I normally simply look for a beer foam type stuff in radiator neck but in nowadays cars you sometimes don't even have that option. So maybe do exhaust test. They sell things for that in parts stores.

Don't fix it if it ain't brok
If it's brok, fix it right away.

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4 years 7 months ago #134796 by barneyb
Replied by barneyb on topic $1500, Still Overheating!
Yeah, sounds like that first failed block test was giving the correct answer.

They say dream big. Well, my dream is seeing a C-5A acrobatic team doing the star burst with smoke.

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4 years 7 months ago - 4 years 7 months ago #134797 by PatriotSpade
Replied by PatriotSpade on topic $1500, Still Overheating!
After the first block test, a second block test, compression test and a leak-down test were both done and it passed all with flying colors. Also, there seems to be no loss of coolant.
Last edit: 4 years 7 months ago by PatriotSpade.

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4 years 7 months ago - 4 years 7 months ago #134807 by barneyb
Replied by barneyb on topic $1500, Still Overheating!
When you write overheating what do you mean? If the only symptom is a high reading on the dash gauge what does the ECU report as engine temperature?

Another possible route is to buy your own block test kit. Sniff the reservoir after driving 35+ mph.

Losing heater output usually means the core has ingested a chunk of air or combustion gas.

They say dream big. Well, my dream is seeing a C-5A acrobatic team doing the star burst with smoke.
Last edit: 4 years 7 months ago by barneyb.

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