Engine overheating

[masta]

Hi all!

I own a T25 D-CAT, and I'm having troubles lately. On the road the temperature is ok, but the radiator fans are on, even with the temperature ok. And when I'm driving on the highway at around 90 mph, the temperature  is ok, but if I drive up a slope at the same speed, then the temperature increases suddenly around one or two bars in the dashboard. I have changed the thermostat but with no changes.

Does anyone have any idea about what is happening? A blown head gasket? 

Thanks for your comments!

[Duggerz]

A blown head gasket would certainly be a possibility, as would a blocked radiator. Given that it's a 2.2 I'd say the head gasket is more likely. If it is, it will definitely be pressurising the coolant. When the engine has cooled there will be a hiss if you remove the coolant cap as the gas escapes. Can be confirmed using a sniffer. As far as I know these aren't prone to blockages in the cooling system, but if coolant has never been changed it's possible. If the coolant is discolored that's a clue. Failure to change the coolant also makes head gasket failure more likely with aluminum heads due to corrosion. Hope this helps

[masta]

Thanks Duggerz!

The coolant has been well serviced, and the old was always clean when I changed it. The water pump was leaking a couple of months ago so I changed it. There's a small amount of pressure when cooled, but I thought it was normal.

If the head gasket is faulty, I don't understand why the coolant is not dirty with oil, or why the temperature only increases when driving uphill.

[Notoyboy]

Are you saying the fans are on with the temperature gauge showing normal?  Sounds odd to me.  Are the fans on all the time?

 

[Duggerz]

Hi Masta, thanks for your reply; uphill driving puts loads more pressure on the engine, and it may be that the leak is slight and at the moment is only acting the vehicle on inclines. You have changed the water pump so that is eliminated. Coolant has been changed so unlikely there are blockages. Really though there should be no pressure in the rad when cold any any appreciable hissing or pop when you remove the cap indicates a leak. I'd have it checked with a sniffer asap.

[Heidfirst]

could also possibly be an airlock

[masta]

Notoyboy: yes, the fans are on even with the gauge showing correct temp. And thats weird, I want to change the sensor, any hints about where to buy it online?

Duggerz: I still think that it's normal to hear a pop sound when removing the cap, any hot liquid expands when hot. And I agree with you, there may be a leak and it is showing slightly, at the moment only uphills.

Heidfirst: I understand airlock as some blockage in the radiator, I checked and the fins are free.

[alan333]

I'm pretty sure the fans come on with the air con too.

[masta]

Yes you are right, they come on and stay on until you switch off the air con. In this case, the air con is off.

[Duggerz]

Heidfirst has a good point about airlock, but that would normally happen only when the coolant is changed. You mentioned that the coolant has been maintained, when was it changed, recently?

[masta]

the water pump was changed two months ago, it was leaking, and the thermostat has been changed last weekend together with the coolant.

I've been to the dealer, and he says it's the head gasket, even worse, he says the block or the head may be deformed and the solution is to install a reconditioned engine..... around 3k euros. I'm still shocked.

Next thing I'll check is the cleanliness of the fins of the rad, and then the rad inside itself.

[Heidfirst]

13 hours ago, masta said:

Heidfirst: I understand airlock as some blockage in the radiator, I checked and the fins are free.

No, it is when essentially a large air bubble exists in the system somewhere & prevents the coolant from flowing around properly. This can actually lead to a failed head/head gasket from localised overheating.

Did this only occur since you changed the water pump (I presume that you lost coolant & had to top up)?

[masta]

Nops, the level of coolant has always been perfect.

I had to change the water pump because it was leaking, and now I think it was for the extra pressure there was in the system. It was after changing the pump that I have been experiencing this ups and downs in temp, it never happened before.

[Duggerz]

Even though the coolant level looks fine in the catch tank, there could still be an airlock in the system that would cause that localised overheating. Having seen your comment about the overheating only happening since the water pump was changed I'm inclined to believe this was the case here. It's true that if the head gasket failed because of carbon buildup then the block and head would be damaged and require an engine swap, but in this case I'm not so sure. Certainly the head would need to have the tiniest amount possible skinned off to ensure it's flat, or a replacement found Do you see characteristic white marks around the coolant finger cap area on the engine cover that are indicative of head gasket failure?

It sounds like the failure is at an early stage.

[masta]

Sorry but I don't get your question. What do you mean by white marks around the coolant area? 

About an airlock, I'm sure there was none, as I did what I always do when changing the coolant, start the engine and wait until the fans get on twice.

Now I consider two options: one is a head failure, and the other is a radiator partial blockage.

[thom1983]

The head is a known fault on the 2.2 and with the white goo and would expect head gasket failure

Sent from my iPhone using Tapatalk

[Konrad C]

When I change coolant or replace the radiator a couple of years back (old Avensis), I remove the airlocks by squeezing as much of the hoses, including the heater hoses. I do this during warm up and a little after the thermostat has opened. Then I replace the filler cap and make sure the coolant is topped up in the expansion tank. After a journey and when the car is cold, I check the coolant level in the expansion tank, which normally drops a little. Top up as required.

The point is, that by squeezing as many hoses as possible, there is a good chance of removing air locks.

Masta (Pempin), Duggerz question - Is there any mayonnaise like substance on the inside of the oil filler cap? This means that there is moisture mixing with the engine oil. Normally it occurs if the vehicle is used a lot for very short journeys and the oil has not been changed, but is one of the signs of head gasket failure.

If the car is going up hill and the temperature rises, but the facing downhill the temperature drops, then the system has an airlock or blockage. May be a collapsed hose! 

As mentioned by others, the AD diesel engine is known for head gasket problems.

Edited November 3, 2016 by Konrad C
Additional info.

[masta]

Thom1983, that information has been already mention in the post, sorry.

Konrad C, the coolant is cristal clear, no oil signs, no mayonnaise like substance. It also appears to me like a blockage somewhere, the question is where and why, as the coolant has been well serviced and I can't picture where that blockage comes from.

I also think that if there were a deformed block or head, the problem should be there, but I don't know if it also possible that the problem shows only uphills and then normal. I mean, I drive at 80-90 even 100 mph with no problem, but when driving uphill at, let's say, 90, the problems shows up. And the coolant is clean, no oil signs, there is a pressure built up after driving uphill, but nothing remarkable after driving along plains and no temperature rise.

[Heidfirst]

12 hours ago, masta said:

Sorry but I don't get your question. What do you mean by white marks around the coolant area? 

if the head/head gasket has gone then the coolant system will be pressurized more than it should be & the pressure relief valve in the expansion tank should release, spraying coolant over the area around it - the Toyota coolant is pink but dries to a whitish residue mark.

[masta]

I've been checking the car a minute ago and the results are quite bad. I turned on the engine from cold, and took it to driving temperature. The bad news is that I can see some bubbles coming out of a small tube which goes from the middle level of the rad to the expansion vessel (don't know the term for that tank on top of the rad), and although the coolant is clean, I assume there's some "air" coming from the cilinders to the radiatior through the refrigeration circuit.

So it looks like I have a faulty cilinder head!! Frustrated is how I feel.

[funcaul]

Hello masta. I am currently having the same problem with my Avensis 2004 T25. Please how did you finally solve this problem?