Bad Radiator Signs? Here Are 7 Sure Symptoms to Look Out For

Before I could explain what I meant by ‘bad radiator symptoms’, she fired again: ‘But I only just bought this car—and you assured me that the Lexus is not only reliable, but this one was well taken care of, and there was nothing to worry about!’

Now, I knew, without being expressly told, that a lot was coming my way and I needed to handle it with the utmost care and tact.

I asked Jane where she was and taking the keys of my vehicle, started off to see what her challenge was.

When I got to where she was had been stranded, I saw the vehicle, parked and looking miserable. Jane was sweating by it and I’m sure, regretting why she opted to buy a vehicle in the first place.

Quietly, I opened the hood (she still had it closed shut) and took a look: I had never seen such a coolant mess in my entire life as an auto DIY mechanic.

1. A Jump in Your Temperature Guage

The instrument cluster of modern vehicles (including Jane’s Lexus) is quite an engineering feat: it is meticulously engineered in a near-perfect manner.

Being the near-perfect machine that it is, if something goes wrong (and it’s an important issue), the instrument cluster illuminates – and relays the issue to you back in your view as the pilot driver.

This vehicle design logic holds for things as critical as the temperature of your vehicle, largely controlled by the radiator housing the coolant responsible for regulating the engine temperature.

If you’re looking for bad radiator signs (like I indicated to Jane and innocently provoked her to anger), this is where you need to start.

A compromised radiator won’t be able to hold the right amount of coolant necessary to keep an engine at optimal operating temperature and as a result, the temperature gauge is going to spike up – without warning, causing the gauge on the cluster to shoot up, correspondingly.

Usually, the temperature gauge needle of most modern vehicles rests in the middle of the gauge – after a few minutes of driving. This is known as the optimum operating temperature. At this temperature, the best fuel efficiency is achieved and generally, the motor runs at its best within this range.

A bit more and the fans kick in to keep things back in the middle; a bit lower and the fans go off to bring things up to the expected range. This temperature spectrum ranges from 190 – 220 F (90 – 104 C) and is largely manufacturer and engine dependent.

A sudden jump in the temperature gauge, unfortunately, may be caused by other issues (such as a compromised cooling fan, low coolant levels, a bad radiator cap, etc).

However, because the radiator holds the principal cooling means of a vehicle (coolant), it makes sense to inspect it first (and make sure that it’s okay) in the event of a sudden spike in the temperature gauge of an ICE vehicle.

2. Coolant Mess

The second of the bad radiator signs to watch out for is a coolant mess. This appears counterintuitive – but allow me to explain: it’ll make sense when I’m done (promise).

A vehicle’s radiator can do its engine cooling job because it actively holds coolant – and acts as a reservoir from which coolant launches, circulates, and returns to it.

Unfortunately, like all wear and tear items on a vehicle, the radiator (mainly through its fins) loses integrity (due to many cycles of expansion and contraction) and compromises this coolant.

Instead of being channeled properly into hoses and maintaining the neatness (and focus) it ought to, the coolant begins to find its way outside – and randomly below its leak points.

These leak points, sometimes, align with the rotation of the cooling fans – which completes the mess to areas such as the compressor and ABS pump – if they’re close.

The net result? A bazaar of red, orange, pink, green (or whatever color your coolant is), everywhere in the engine bay!

The good thing is that this doesn’t happen overnight: it usually starts with a small leak that degenerates into something massive and challenging to the eye (if not tackled on time).

Leaking coolant, especially on the body of the radiator itself, is a positive symptom of a bad car radiator (and conclusive for that matter).

You should attempt to catch this at the earliest possible time – something I believe Jane missed.

This is also a good reason to always use coolant (even in the summer/tropics) – as water simply dries off, leaving no residue to point out what’s happening.

3. Poor Heating

On cold winter (or harmattan) mornings, when you turn on the heat in the cabin of your vehicle, what happens is that the hot coolant, passing through the heater core is how you manage to get heat in the cabin.

For your heating system in the vehicle to work flawlessly, you must have a way to retain the hot coolant (coolant at operating temperature, that is) in the radiator (after it travels around the engine, cools things off, and returns to the radiator to be cooled itself).

A bad radiator won’t be able to hold this coolant anymore – and not only will it fail at this, but because of the failure, there won’t be enough heat flowing into the cabin as you’d expect (or as you usually experience).

If you ever experience a lackluster performance from your cabin vents when you power on the heat, don’t hesitate to check on the radiator to be sure that it has sufficient coolant flowing from it.

If it doesn’t you’ve found your culprit: your next challenge would be to figure out where the coolant is going, instead of remaining in the system and doing its cooling job.

4. Increased Heat in the Cabin

Closely related to the above, one of the bad radiator signs, right after a failure of the cabin heater to function as intended, is general increased cabin heat.

This bad radiator symptom is a very tricky one, however, so you need to pay attention here to catch it very early.

You see, a vehicle’s cabin (running AC, heat, or nothing), usually has a temperature range that you get used to, after a while.

However, if you’re paying attention to your surroundings and are sensitive to changes, sometimes, the vents offer poor cooling with the AC, below what you expect.

If you’re using heat, this happens when you power on the heat and things are taken to the next level, over and above what your settings should have ensured.

Or, generally, you experience the cabin suddenly getting warmer than it should, when it otherwise has no business doing so.

If any of these signs occur while driving, you’re likely dealing with an overheating issue of the engine and the radiator failure remains a major culprit when it comes to the reality of overheating engines.

5. Unexplained Coolant Loss

This is one of the most straightforward bad radiator signs to watch out for: it’s also usually non-complicated and quite easy to decipher.

Most modern vehicles have a clear coolant reservoir that houses coolant overflow, much like a traditional expansion tank. From this reservoir, coolant is ‘sucked’ back into the radiator to fill it up, as the vehicle is parked and general temperatures in the engine fall.

However, the coolant reservoir doesn’t only act as a reservoir, it also functions as a ‘receptacle’. By receptacle, I mean it’s where you traditionally ‘top’ up the radiator, if you need to, without necessarily disturbing the peace of the radiator cap.

The only challenge here is that a radiator, traditionally, doesn’t need to be topped off periodically.

What this means is simple: your radiator coolant is good for its time in the radiator – which can range anywhere from two to five years.

However, when the coolant reservoir begins to drop below the safety levels periodically, then, there are only a few reasons for this with the major one being a compromised radiator.

Note, however, that a burst hose, a compromised water pump seal, etc. can also cause this manner of leak. In my many years as a DIY mechanic, the radiator is always, almost the culprit in most of the cases I’ve taken a look at, even if it appears innocent (and the leak isn’t immediately obvious) because of its positioning and general orientation in the vehicle.

6. Strange, ‘Windy’ Noises

The 6th of the bad radiator signs you need to specifically watch out for and take seriously is a sudden, strange, ‘windy’ sounding noise coming from the engine bay.

A caveat here: you’re likely not going to hear this if you’re the type of vehicle owner who loves to maximize the use of their sound systems whenever they’re driving.

However, if you’re like me and prefer to listen to your engine note instead as you drive, you’re going to catch this one sooner rather than later. The point is also going to make the greatest sense to you.

If it makes sense for you to continue with this point, the whole essence is to pay attention to the cooling fan, especially when using the air conditioner or when the fan comes on.

Normally, the fan will work without any incident and stop, in a traditional start and stop manner (or how it was designed).

However, if the coming up of the fan coincides with a ‘windy’ sound (as you get when you cover a rotating standing fan with nylon), you’re likely dealing with a compromised car radiator, leaking into the cooling fan blades and the blades, in turn, splashing away the fluid unto different components as shown in most of the photos I’ve shared on this article already.

The smartest thing to do, should this happen, is to recognize it as a bad radiator sign, pull over, and inspect.

This is what Jane failed to do and this is why, without question, her situation got that messy and challenging in the first place.

Let’s proceed to bad radiator sign number 7!

7. Coolant Contamination & Discoloration

A vehicle’s radiator is generally a closed and sealed-up unit, without any interference from outside. However, for some strange reason, if you find out that you have debris or residue present in the coolant reservoir, then, without question, you have a compromised radiator that had led up dirt into the system.

I’ve attached a photo to show what I mean by this.

Unfortunately, many car owners today don’t bother with opening the radiator reservoir to take a look at the quality of their coolant, especially since the unit is transparent on most models and opening isn’t necessary to see what is inside.

Unfortunately, this dirt isn’t visible from the outside.

However, occasionally doing this will open you up to potential radiator challenges even before they happen, preventing any sort of mishap along the way as you drive and try to make your vehicle serve you faithfully, reliability-wise.

Debris in the cooling system as evidenced by dirt in the coolant reservoir could also be as a result of rust, building up in the system.

Either an outrightly compromised radiator or one that has begun to rust slowly from the inside will lead to overheating – and this is what you don’t ever want for your vehicle!

How to Stay Ahead of the Game Like a Boss

This article has covered 7 bad radiator signs to watch out for to avoid the challenge Jane found herself in: being stranded with a steaming vehicle by the roadside instead of honoring an appointment she had.

So, how do you prevent all these from happening, in the first place? It’s simple. Here’s how:

1. Pay Attention

Jane was angry with me for not paying enough attention when I inspected her Lexus and gave it the nod of approval.

I understand that she was frustrated but that much detail is outside the scope of an inspection (it isn’t a deal breaker, BTW, only a negotiating leverage that may only take off a few hundred dollars).

The real attention that needs to be paid, however, is to the routine inspections that need to be taken periodically, the looking around the engine bay from time to time, the taking a look at the coolant reservoir, and generally, the taking of any coolant debris seriously.

2. Handle Repairs Promptly

Because most radiator related issues don’t immediately escalate to something demanding right away, it’s tempting to leave them on and keep postponing the repairs as time ticks by.

Don’t!

If you choose to postpone repairs related to the radiator (or cooling system generally), you’re going to be stranded sooner than later – a situation no one truly wants for themselves.

3. Watch Your Cluster!

Finally, the best thing you can start doing right away to stay in charge of your cooling system like a true boss is to watch your cluster at all times.

This is one mistake newbies commit now and then that leads to costly repairs, down the road.

Assume that you ignore all the points above; however, if you keep an eye on your cluster and immediately pull over when the temperature gauge begins to shoot past the midpoint, you’ll be fine – with the worst-case scenario resulting in your being stranded, nothing more.

However, your engine will be fine and immediately after the challenge is positively identified, you’ll be good again and on your way.

Paying attention helps, after all. Do not forget/ignore this (even if you forget/ignore everything else).

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