On the radiator cap there is light brown pudding/paste deposit.

In Nissan model year 2005-2010 Pathfinder, Xterra and Frontier SUVs have defective radiators. There was settlement about a defect that permits cross-contamination of engine coolant and transmission fluid, ultimately causing the radiator and transmission to need substantial repairs or fail entirely.

I bought my 2006 Nissan Pathfinder on 3/15. Within one month it needed a new transmission and new radiator. I rarely check the coolant but one month ago I notice the reservoir was low and I checked the radiator cap. The cap has a light brown soft paste on it. Should I get a engine coolant flush

Experienced mechanics share their insights in answering this question :
Hello Daniel, thank you for writing in. While these issues are frustrating, it may be as simple as needing to flush the system. Yes when you flush the entire system, you should be able to flush the water pockets as well. This all depends on how clogged the system is and how well the system is flushed. You will also want to make sure you are using a quality coolant when you replace it after flushing it. Keep an eye on the engine for any signs that the head gasket is damaged. If you suspect the sludge is oil contamination, then this is where it would be coming from. For any further diagnostic help, contact our service department to schedule an appointment.

How to Identify and Fix Common car Problems ?

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The brown sludge you are referring to is often caused by rust or breakdown of the metallic and rubber components that comprise your cooling system.
What does discoloured water mean? If the water is brown in colour, that is an indication that you have sludge in the system. This is a build-up of rust and dirt from inside the pipes and over time it will not only compromise the performance of the system but can cause significant damage.
If your coolant is dark, looks brown, or you see particles floating around, it`s time to for a flush and fill. Save at your local NAPA AUTO PARTS store.
Coolant that appears to be chocolate milk contains some kind of oil. It is possible that transmission fluid leaked from the cooling system. Oil can also enter the coolant through the oil cooler located beneath the intake manifold.
If your head gasket is damaged or blown, engine coolant can leak into the passages for the oil and mix with it, which results in a milky oil cap. If left untreated, a blown head gasket can damage the cylinder heads and bearings and crack the engine block.
Coolant in an unhealthy engine is milky-looking. Milky coolant can appear grey, dull, dark, or white. Coolant that is milky and dull in color can indicate a significant issue with the head gasket that needs immediate attention. A vehicle`s head gasket is fitted between the engine block and cylinder head.
Remove the radiator cap and pour distilled water into the radiator until full. Replace the cap, then start up the vehicle and let it run for 10 to 15 minutes. This will work the distilled water into the engine, flushing out any loose debris or corrosion along with the last of the old antifreeze.
Rust in the cooling system can also be caused by air getting into the radiator when the engine cools down. As the coolant cools down, it contracts which can cause an air pocket.
Milky, frothy oil on the dipstick could mean you have coolant leaking into your oil pan, but doesn`t necessarily mean a bad head gasket. This symptom is too often mis-diagnosed as a bad head gasket with unneeded repairs performed. There are many other things that can also cause this and it is rarely a headgasket.
Oil and coolant leaks are common issues on many vehicles. Just because you see a leak doesn`t mean you have a blown head gasket. If you see the majority of the oil or coolant seeping out from the engine block though, it could be an indication that the head gasket is no longer maintaining a seal.
Normally it`s either a cracked head or a cracked block, usually caused by cold weather with improper antifreeze or by running the vehicle without proper amount of coolant or engine cooling fan issues.
It sounds crazy, but Coca-Cola works great for cleaning radiators. One or two fills with the coke (let it sit for 2-4 minutes) and rinse thoroughly with distilled water. The acidity of the coke removes the gunk in the radiator as well as a fair amount of loose rust.
Radiator Hose Troubles:

Another symptom of a clogged or faulty radiator is if the radiator hoses are hot to touch. The hoses carry the car coolant from the radiator to the engine. If the hoses are hot, it means that the coolant is not flowing correctly and the engine is overheating.

Sludge can block the valves of radiators, and even block the pipes themselves. When this happens less water can flow through, and the entire system is therefore far less efficient. This has knock-on effects, the most serious being its effect on pressure.
The good news is that you can keep your engine cool by conducting a coolant flush on your own. Even if you`re not super knowledgeable about cars, it`s easy enough to replace your old coolant with a fresh supply.
For this, you need a container (large enough to accommodate the reservoir), fill it with bleach, dishwashing liquid, and water. Now place the reservoir into the container and allow it to sit for a few hours, and you can also let it stay overnight.
Besides removing the used antifreeze from your radiator, other benefits to flushing your radiator can include removing the rust and scaling that has built up on the radiator as a result of the old coolant, as well as lubricating and lengthening the life of your water pump.
If coolant is leaking into your motor oil, it will turn the oil tan or milky on the dipstick or underneath the oil cap. Leaky coolant can build up underneath the oil cap, too, so check that monthly.
If you discover a milky brownish-yellow substance that is similar to the thickness of a milkshake, you probably have a gasket leak. The milky substance is oil mixed with coolant that has seeped past the head gasket contaminating the engine oil.
If you have an older car, say that came with green coolant, you can flush it all out and put the newer style coolant in and then change it every five years or 150,000 miles. It`s perfectly backwards compatible if you want to do that.
The main difference between coolant & antifreeze is their purpose. Coolant regulates overall engine temperature, while antifreeze is used to protect the coolant from the cold. Both mixtures are vital for keeping your car running correctly, so check radiator fluid levels and top them off when required.
The answer to this is a firm `no`. Because coolants are no longer classified by colour, it`s impossible to tell if two products will mix safely within the system. Get it wrong, and it could cause a blockage that will wreck the cooling system and lead to significant repair bills.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

On the radiator cap there is light brown pudding/paste deposit.
ANSWER : Hello Daniel, thank you for writing in. While these issues are frustrating, it may be as simple as needing to flush the system. Yes when you flush the entire system, you should be able to flush the water pockets as well. This all depends on how clogged the system is and how well the system is flushed. You will also want to make sure you are using a quality coolant when you replace it after flushing it. Keep an eye on the engine for any signs that the head gasket is damaged. If you suspect the sludge is oil contamination, then this is where it would be coming from. For any further diagnostic help, contact our service department to schedule an appointment.

No dash lights, back right tail light is out, no parking lights. Brake lights work though as does head lights.
ANSWER : Hi there. In many cases, when you have electrical problems like you’re describing, it’s caused by multiple electrical component failure. It’s likely that a few electrical relays are not working; especially if you have systems that utilize the same components (such as your brake light and tail lights). I would recommend having a professional mobile mechanic come to your location to complete an electrical problems inspection first, so they can pinpoint what is damaged and recommend the right repairs.

Abs light, emergency brake light, steering wheel assist light, engine light, EPC light, traction control light
ANSWER : Hello, thank you for writing in. The vehicle does utilize a lot of the same sensors for these systems. Are there any other codes that are coming up when this code appears? If so you will want to take these into consideration when processing the repair and making a diagnosis. The module may be bad, and replacing it should fix the problem. The lights should turn off once the main computer recognizes the new module and the sensors sync up. If you believe the sensors need to be cleaned you may do so. Do as minimal as possible to make sure you are not damaging the sensor or disrupting the wiring inside. A bad connection would make the lights stay on. With so many lights that are effected by the module being illuminated, the module is likely bad or does not have a connection. Check the connection first and then resort to replacing the unit. For more help with these electrical tests, contact our service department.

Radiator hose from cap to coolant reservoir broke off just below cap on radiator. Can repairs bbeen done without changing radiator? 2010 Nissan Armada
ANSWER : Hello – although this cooling system hose looks much like an octopus, it can be changed without removing the radiator. It does require small hands and a bit of "technique". For assistance, I would recommend a radiator hose service by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

Battery light goes on when I start car then turns off, if I rev engine light comes back until rpms go down. Abs goes comes on/off
ANSWER : Batteries can die due to faults in the charging system so ideally a suspected "faulty" battery should be load tested before a decision is made to condemn it. The only exception to this rule is if the battery is already clearly "old" (greater than 5 years) but even then once you put a new battery in, as a replacement for a "dead" battery, you have to comprehensively check out the charging system. Diagnostic Trouble Code P0460 will result in disruption of the dashboard fuel gauge’s ability to accurately report your tank’s fuel levels. The fuel gauge readings may be erratic, or read somewhere off scale. Vehicles equipped with a low fuel warning light feature may also suffer from erratic low fuel warnings in the event of a code P0460. Unless the P0460 code has been reported alongside other trouble code, all of the vehicle’s essential systems should otherwise function normally. I would recommend that you request a check engine light diagnostic to first resolve the fault causing the P0460 code to set. The check gas cap light warning light could be due a faulty gas cap and/or small leaks in the EVAP system.

2012 equinox reduced power light engine light and traction light came on. Lost a lot of power got home and all light except engine
ANSWER : Your car has what is called a "safe mode" that will be engaged by the computer when it detects that something critical has gone wrong related to any of the major components in your engine chassis or power train. This may be related to a number of things, most of which should have been registered in the computer when the check engine light came on. I recommend having an expert from YourMechanic come to your location to inspect your check engine light and diagnose any codes registered by your vehicle’s computer.

ABS light on, ESP light on,Traction OFF light on, engine light on, rides perfectly OBDI reads only Front Right Wheel Speed Sensor
ANSWER : If a faulty component is still in place, the fault codes will return almost immediately after clearing them. ABS, ESP, and traction control systems all rely on input from wheel speed sensors to determine as the name implies, the speed of each wheel. When a wheel, or wheels are spinning faster than others due to wheel slip or the vehicle is sliding, the ABS and ESP systems can reduce throttle input as well as apply braking to an individual wheel or all of them if needed. With a wheel speed sensor fault code stored, these systems cannot determine the rate that all 4 wheels are spinning and sets a fault. That is why the abs/esp light is on. The system should be scanned by a certified technician and the wheel speed sensor replaced if found to be the cause. The warning lights will stay on and these systems will not function as designed until the fault is corrected. These lights do not come on to indicate a need for routine service. Rather they only come on when a component in the system is at fault.

signals, daytime running lights are not working, park brake light on dash is on steady and chime is dinging steady 4×4 wont engage
ANSWER : This is likely a brake light switch problem. I would suggest testing the brake light switch which should be located down by the brake pedal. This may also be a computer problem as well as indicated by the other lights on in the dash. I would recommend having an expert from YourMechanic come to your home to possibly replace the brake light switch and diagnose with a scanning tool which will download useful data from the truck’s computer indicating what specifically the problem may be.