I'm hoping someone can share some insight on an issue happening with my dad's truck (01 QX4 189,000 miles)...

A couple weeks ago, his truck was overheating and leaking coolant. We had it towed to his house for him to inspect the next morning when there was light out. My dad was stumped and did not see any obvious leak (he's not a mechanic by any means) and spoke to a nearby mechanic shop. They recommended that he top off his coolant and since the shop was less than 5 minutes away, to drive it to them.

After keeping the car for a couple days, they replaced the radiator (Denso), radiator cap, thermostat, added coolant, labor (almost $850 for parts, labor, taxes which I still think seems high). The tech mentioned he was concerned about the head gaskets due to the way the previous radiator had blown pressure cracks into the radiator. Apparently, they did some "basic" tests and confirmed the head gasket was fine prior to replacement.

Fast forward 50~ miles later and my dad noticed the truck was blowing cold and was leaking coolant again. He had the car driven back (not far from shop) and the mechanic kept the truck for another couple days. Only this time, they are saying the truck has a blown head gasket (ran additional tests?) and they would credit my dad for some labor (not sure how much, but will be determined).

the shop proposed 2 scenarios:

1) replace headgaskets, machine heads, ~$4000 for labor and parts
2) swap engine with another low mileage engine ~$5500

Is this shop outrageous? Any other possible causes to his issues? Also, at 189,000 miles, what are some possible causes for head gaskets. I will update additional info as I find out more. Right now, my dad is thinking he needs to start car/truck shopping.

Any advice is greatly appreciated!

Over ten years on this forum, and I can't recall any issues being raised about head gaskets on the 3.5 engine.
If it's blown, then it's very unusual for this engine.
$4,000 to replace head gaskets seems awfully high. I'm guessing your mechanic is not that familiar with this vehicle and engine, and is inflating the price to cover his butt.
I'd get a few other quotes, maybe even one from a dealer.

Yep, that's WAY high to swap HGs. However, if the head or heads are warped, that's about right, because they have to be resurfaced or replaced.

Head gasket goes bad typically from overheating. So, a compromised cooling system can certainly cause a bad HG.

The tech comment: "concerned about the head gaskets due to the way the previous radiator had blown pressure cracks into the radiator" is basically crap. At 189k miles a stock radiator should have been replaced at least once. They simply don't last long. A failed HG on't "blow out" a radiator - radiators fail, THEN the head gasket blows (from overheating).

A simple test would have been a pressure test and compression test after replacing the radiator. Typically, a bad HG will have one of two symptoms: water in the oil (oil will look like melted chocolate ice cream) or oil in the coolant (less common) or the exhaust will blow white smoke, and plugs will typically be whitish and crusty.

A low mileage takeout engine for that truck can be had for around $1500, but the R&R is usually another $1500, plus little parts here and there.

What part of the country are you in?

I appreciate the responses. Out in Denver, CO.

Are there any common issues that duplicate the head gasket/cooling system issues. I'm hoping these mechanics don't know this model well and it could be something easy to fix.

Not knowing just how the radiator failed, and a proper radiator cap should relieve pressure, but a blown head gasket can produce high pressure in the cooling system. So a bad head gasket could damage a old and tired radiator, but if it was that bad the shop should have figured that out. Maybe not before they replaced the radiator, but before they returned it to your Dad. The price sounds high, but not crazy high. And until they pull the heads, assuming it is the problem, they won't know if they can be surfaced or if they need to be replaced or if the deck of the block is warped. I'm neither defending or criticizing the shop, but until they get in there they can't really give a firm price, except for a replacement engine.

My discussion below is based on experience with the 3.5 engine, but could you clarify if you have that one or the 3.3?


Yes, it's possible that any one of the causes of overheating could end up tweaking the block/head interface and leaking from that head gasket area.
Some overheating causes are:

• Thermostat
• Water control valve (rear thermostat)
• Accessory belt system
• Water pump
• Radiator fan shroud
• Cooling fan clutch
• Cooling fan blades
• Radiator. Cracking plastic or the metal crimp coming apart
• Radiator cap
• Head gasket. Which is technically a result of overheating...unless the head gasket has already been worked on.
• Other coolant leaks, which includes weak or damaged hoses

Of those, the ones I would focus most in an R50 are the cooling fan blades, radiator, cap, water pump seals.
In my experience, a properly working radiator and cap will not be damaged by a bad head gasket; however the reverse is very likely.

Anecdotal
I had a 2002 Qx4 with 313,000 miles and an original radiator. However, it does not surprise me to have to replace a 2000-2006 era Calsonic radiator when the vehicle has approx 150K miles. It was a weird time for Nissan radiators.
At the same time, I had another Qx4 that constantly overheated, but we came to find out that whoever had replaced the engine the first time had done a crap job of keeping the head and block surfaces smooth while rebuilding it.
*Oh, that radiator was good and was used when the engine was replaced.
Most times I prefer buying a warrantied engine to rebuilding a damaged engine.

Problem vs. Symptoms
All along, it does not seem like the source of the leak has been identified. I assume it's external, right?
There is another possibility. On the rear surface of the heads, there is a crossover tube that might leak right where the ends mate to the heads.

My recommendation is to test it again, whether yourself or a different shop. I mean the thing has already overheated and thrown up, right?
Drive the vehicle long enough to warm it up then leave it running in park and when coolant starts to drip, look in the engine bay (remember the back side of the heads).
P.S. The engine heats up way faster with the cooling fan decoupled, but I'd only recommend it for brave hearts.
OR
Put some UV dye in the system and when it leaks, trace the source. UV tracer kits can be had for cheap from most auto parts stores
P.S. I usually run distilled water in testing. Coolant can get expensive, especially if it keeps leaking out; but that is personal preference.
OR
Have them (or yourself, or other shop) use a pressure test kit to try and find the leak.

The testing might show some interesting results.
I'm not saying that you certainly don't have a bad head gasket, but I would sure gamble another $50 in testing if it has the potential to save me $4000+
At this point, I think the shop's proposals are akin to burning your house down when you see a spider in your bedroom. Yeah, the problem will go away, but in the end you wonder if you could have achieved the same result with less disruption.

Legend11 wrote: ↑

Tue Dec 18, 2018 4:23 pm

the shop proposed 2 scenarios:

1) replace headgaskets, machine heads, ~$4000 for labor and parts
2) swap engine with another low mileage engine ~$5500

Is this shop outrageous? Any other possible causes to his issues? Also, at 189,000 miles, what are some possible causes for head gaskets. I will update additional info as I find out more. Right now, my dad is thinking he needs to start car/truck shopping.

Any advice is greatly appreciated!

I'd say both scenarios are too expensive for your truck with that many miles and then what if something else expensive flares up, like the trans or ???. The labor cost is a killer and it's just not worth it unless you can do that kind of work yourself.

If it were me, I'd determine for sure it is the head gasket that's leaking and fix the cause of the overheating, then add a bottle of the best rated (youtube reviews) "head gasket sealant" you can find and see how that works. Drive it easy and hopefully you will get a few more miles out of it, maybe even a few thousand. Consider every mile driven to be a bonus.

Cheapest and easiest is a coolant combustion contamination test. It's a test strip you dip in the coolant and it will tell you if there is combustion elements in the coolant and is a pretty good quick test for a blown head gasket or a hole in the cylinder wall (a diesel thing). Next easiest way is to use a compression tester hooked to an air compressor to find which cylinder has blown because the coolant will bubble when you find it. Go shopping for a small enthusiast shop, your cost should be around 2K for the gasket repair. Funny enough its usually faster to pull the entire engine than pull a head with it installed.

Update:

My dad went ahead and purchased a used Honda Accord. He's going to put a pin in the QX4 project until Spring/Summer (currently parked at this house).
As planned, we are going to try to get a second opinon on the blown-head gasket diagnosis. If the head gasket is in fact blown, we would prefer to pursue an engine swap vs dealing with the head gasket repair.

I've been checking around on Ebay and pleasantly surprised to see low-mileage VQ35DE engines around the $1000-$1500 range. Are there any recommended companies with any guarantees/warranties on the replacement engine?

We will need to shop around for a mechanic to do the swap. Based on the previous comment, should we expect to pay around $1500 for the labor portion?

The truck is in relatively great shape (no rust) and worth the effort. My dad would feel much better dumping $2500-$3k in an engine swap rather than finding another SUV for the same amount of money. We've also had a bad experience with a head gasket repair on another vehicle a long time ago; I just don't have confidence in the quality of work being done to repair a head gasket. It feels like a swap is more reliable method to resolve this issue.

Any other advice on this project? As mentioned, we won't mess with it for a few months. My dad is currently enjoying his new Accord
As always, I appreciate the help and advice on this forum.

Since your dad has a new car and is resolved to scrapping the engine I'd still suggest trying the head gasket sealant in a can. There's a few Youtuber's that have had good results and some not but only cost is about $30 to try it.

My dad's truck has been parked since I originally posted this thread and it's now time to diagnose it.

We tried to take it to another mechanic yesterday.
Coolant is pouring out of the overflow reservoir after only 2 miles of driving. We had to turn back.
At this point, the following has been replaced:
Radiator (Aftermarket Denso)
Radiator Cap (Aftermarket)
Thermostat (main one) (Aftermarket)

Based on these symptoms, do you recommend I try to replace the Water Control Valve (OEM) and Water Pump (OEM) next? Anything else? Before we even begin to explore an engine swap, I want a 100% guarantee that there is a bad head gasket and I'm just not feeling confident with the original diagnosis.

What other parts could be causing coolant to pour out of overflow reservoir like it is. I want to try the simple stuff first. The original mechanic may not know this car like this forum. Thank you for any info.

Below is what you need to go back to. There may be tricks for Nissans I don't know about, but the following pretty much covers all engines. Follow what he says and you should be able to make a pretty conclusive diagnosis. Change parts later, do diagnostics first.

anyonebutme wrote: ↑

Sat Dec 22, 2018 9:37 am

Cheapest and easiest is a coolant combustion contamination test. It's a test strip you dip in the coolant and it will tell you if there is combustion elements in the coolant and is a pretty good quick test for a blown head gasket or a hole in the cylinder wall (a diesel thing). Next easiest way is to use a compression tester hooked to an air compressor to find which cylinder has blown because the coolant will bubble when you find it. Go shopping for a small enthusiast shop, your cost should be around 2K for the gasket repair. Funny enough its usually faster to pull the entire engine than pull a head with it installed.

UPDATE:
I stopped by my parents tonight and re-bled my dad's cooling system with my lisle funnel. I did this once before and his issues came back shortly after so I wanted to throw something slightly different at it tonight. I re-inspected the new radiator cap (provided from mechanic) and it seemed like an odd fitment; I original wrote it off as an odd fit because the cap and radiator were new, but tonight I wasn't convinced. It took it in the house and compared it to pics online of QX4/Pathfinder caps and it was completely different cap. The QX4/Pathfinder one pictured is a complete round circle with 2 round notches on the side and a deeper valve, the one on there was had a more shallow valve (which possibly explains why coolant was so easy to flow into the overflow) and was more "oval like". I went to Advance Auto to pick it up and amazed at the difference in person between the two radiator caps.The install fit much better and didn't feel as forced. The plan is if this works (so far 6 miles of driving and no symptoms), I will buy an OEM one. Time will tell, but the feeling is great that this might be a permanent fix.

At this point I believe there are 2 reasons this cap was incorrect:
1) An honest mistake (although ridiculous). Why wouldn't a professional mechanic compare the original and replacement part?
2) A deliberate attempt to generate an "overheat" symptom to try and scam my dad out of a headgasket/engine replacement.

I always use OEM parts for my preventative maintenance and repairs. Not to mention the costs of labor and markup of parts, this is the biggest reason why I don't like going to mechanics is because they throw whatever aftermarket parts they can get their hands on in the vehicle and you have to second guess the quality of the work.

Wish me luck? Hopefully the original "blown radiator" issue has been resolved. Will keep everyone posted.

My dad has driven a total of 15 miles and so far, no overheating or coolant coming out of the overflow. I'm making my dad keep the heater on while he drives to see how it handles that. He did mention that the condensation tube was dripping which I find unusual because the heater was the only thing on (no AC). I'm going to get into the Climate Control diagnostic mode to see if any sensors/actuators are out. I will most likely consider pulling the fuse from the AC for the time being. What's most important is having an operational truck; the AC isn't as a priority as of now.

Not sure if the compressor running is the most likely cause of stress on the cooling system. At this point, it's just a theory. Please let me know if there are any other ideas. I'm also going to bleed it again with the lisle funnel just to be 100% all the air is out.