CD5 Temperature rises on hills

[SeeMeRollin']

Hay guise.

When rolling down the freeway to and from Newcastle to Sydney, my CD5 temperature gauge rises when going up the large hills...normally it doesn't raise over 1/2 way but when going up these hills it rises up to 3/4...sometimes getting close to crossing the max into the red on the longer ones. It always settles back down after the hill...doesn't appear to overheat significantly...never have problems with it on shorter journeys, only on the freeway. Does this sound normal?

The manual said that its normal for it to rise above half way during hills/hot weather but I'm just not happy with it, makes me feel uneasy.

[bennjamin]

whens the last time the thermostat was replaced ?

Go to HONDA , purchase a brand new thermostat + gasket to suit your car and a 5l container of coolant. Install yourself or get a professional to do it , and that should fix this issue.

[Riviera]

and the radiator cap, check thats still good.

thermostats and caps make the radiator lose pressure causing it to boil

well so do hoses but thats not the problem

[JohnL]

The cooling system is marginal, possibly because of:

Internal blockage in the rad tubes.

External blockage of the rad tubes (debris in front of the rad or the AC condensor).

Fin rot. Some significant area of the copper (or aluminium) fins through which the rad tubes pass in the core are corroded and are no longer adequately radiating heat, which can sometimes be the case even if the affected fins look OK (this is more likely if the rad core has been painted, i.e. the paint holds the fin shape, but under the paint the fins can be nothing but oxide). You may need to pull the rad and have a good look at it.

Worst case scenario would be the begginings of a head gasket problem...maybe. Have you checked the coolant level?

I somehow doubt it's likely to be a rad cap or thermostat problem. The problem doesn't appear to be boiling fluid (doesn't sound like it's getting hot enough to boil even if the system pressure were atmospheric), simply a temp rise when the engine is working a bit harder than usual (and thus producing more heat), which suggests that the system simply can't get rid of enough heat in these conditions, whereas normally when less heat is being created it can.

[SeeMeRollin']

Coolant level is good, its not been boiling or leaking. Colour is good. There is a lot of K's on the car, 240K and I'm pretty sure its the original radiator. It's not a huge surprise that the radiator might be on its way out. I was just hoping...because the manual says this can happen in hot climates climbing hills...that I could keep my money and not worry about it. I guess I should ignore that and have it looked at by the sounds of things...Thanks for the tips!

I've also read that you can see if its a head gasket problem by starting it up cold without the radiator cap on and watch for bubbles...try this?

[Vinnie]

like john alluded to, those symptoms sound similar to the old falcon we used to have, all it needed was a proper radiator flush. after many years and k's the radiator had simply become clogged with rubbish and was only operating at 30% efficiency. it was not a drastically expensive procedure to get it flushed and it didnt require a new radiator. just another possibility i guess.

[JohnL]

My gut feeling is that it's more likely that the cooling system isn't up to par rather than the gasket starting to go, but I wouldn't rule it out. Check for bubbles (don't take the cap off a hot radiator!), but also check for rad hoses that seem to become more pressurised than normal by squeezing the one of the main rad hoses when the engine is fullly at temp.

I'd be more interested in the condition of the cooling fins on the rad core at this stage. If the inside of the rad looks clean and the coolant looks OK then it's less likely that the rad is blocked internally, but again nothing should be ruled out. If it were my car I'd pull the rad out to have a good look at the cooling fins, and while it was out I'd give it a good reverse flushing with a hose.

[SeeMeRollin']

No bubbles. No oil milkshakes found under/around/in the oil cap. *phew*

I did notice small amounts of chalky residue around the bottom of the coolant cap, on top of the radiator, with small encrustations of it down the back between the fan housing and radiator itself...not heaps, and I haven't even noticed a drop in the coolant level...so hopefully I just need a new cap?! When the engines under heavy load, freeway speeds, uphill for extended periods, maybe its just losing pressure through the semi-dodgy cap, enough to get the heat up but not enough for it to catch fire...?

Or could this still be attributed to blocks and gunk and corrosion of the core you think?

[FAT VTI]

any milky residue in your engine bay is prob a leak of coolant which has burnt (it looks like a white chalky mark).
So long as your coolant level is fine then it should be okay. Are your hoses still stiff? or are they really soft. Somebody can probably provide better details, but a softer radiator pipe can prob present leaks at the connections more than stiffer newer piping.

[SeeMeRollin']

Hoses are medium soft, squeezable but there is no residue around any of the connections or the hoses themselves, the only residue is under/around the rad cap which could even be spillage from filling it last time? The rad fans are fine I checked those, they blow a healthy strong current.

I just went for a cruise then to check the pressure in the rad hoses afterwards, they seemed equal...but very hot. Nearly burnt my finger squeezing them. No appreciable difference in either hose, they definitely felt more pressurised after driving then they did when cold though...

I guess I better just goto natrad and get an inspection done. That should only be about 100 bucks eh?

[JohnL]

I'd say you need a new cap, but it only sounds like it's seal is seeping slightly, no big deal (though it will only get worse, so I'd change it now just in case).

The cap pressurises the coolant, but this in itself doesn't cause the engine to run cooler, only raises the coolant boiling point so that when the temp rises above 100° it won't boil. Boiling is bad...

The pressure in the entire cooling system will be uniform, so you won't see any difference in hose 'hardness', they will all be the same.

The fins may be shot, or may not. But how much air the fan draws through the core isn't really any indication. The rad on my CB7 has some areas where the fins are rotten, but not enough area that the rad doesn't work fine (even on hot days with AC on). To check for fin rot this you really need to take the rad out and have a good look.

Pull the rad and run your fingers firmly over the fins (but don't be too rough on it, even good fins aren't all that tough). Rotten fins will collapse and either crumble or fold up easily, or both. Typically fin rot will ocur in an 'area' of the core, and there may be more than one area. usually a small area of rot won't cause a problem since a good core has more heat transfer capacity than really needed, but a large area will definitely cause the sort of symptoms you have (been there a few times over the years).

The only cure for this is a replacement rad, though they can be recored. However, if the core is shot then the top tank is likely to be on the way out as well because over time (years) the plastic that the tank is made from becomes brittle and cracks (never seems to happen to the bottom tank as it doesn't get as hot as the top tank).

While you have the rad out check for fins that are folded over at the very front or rear of the core, this adversely affects air flw through the core. If you find such bent fins then pry them apart to open up the pathway for the air flow. 'Flow test' the rad with a hose while it's out, the rad should be able to flow all the water from a hose on full bore, i.e. stick the hose in the rad inlet (packed with a bit of rag in the orifice), and all the water should be able to flow through from inlet to outlet without creating too much pressure anywhere in the rad.

Hope this helps, but if not then I think you need to take it to someone.

[Spoon-Accord]

bring it to a radiator shop, get it flushed

try taking off the top radiator hose and see if any residue

also remove the thermo to see if it still functions properly,

check if the fans come on at the right time aswell, faulty fan sensor