Overheating issues

[Jackthelemming]

Hi all,

So I’ve got a slight issue with overheating. I’ve just changed my fan switch sensor, Ect sensor and the gauge sensor (the two below the distributor and the one to the rear of the thermostat housing) and have replaced the thermostat housing after I snapped off the bleed nipple from the previous one. Now I’ve bled the radiator and I have a good clear stream of coolant coming out the nipple so I’m confident it’s been bled fine. The car will sit at the right temperature for about 15 minutes and is fine when I drive it however when I stop the temperature goes about 2 notches above the correct temperature. Previously my fans weren’t working - I grounded and tested the fans and the relay is all good and they both work now that I’ve changed the sensor but they only come on for about 15 seconds when I’m idling hot. Bizarrely the ac fan does not come on at all when I switch the ac on? The previous owner removed the condenser but I’m sure the fan should come on when I turn on ac despite there actually being no air conditioning or condenser. To clarify - both of the fans engage for about 15 seconds when the car is idling hot and the temperature does drop very slightly but not to the correct temperature. I’m at a loss what could be causing this. Did an oil change less than 3 weeks ago so there’s the right amount of oil in the engine! Any ideas what could be causing this? Any help is greatly appreciated!

[Scott560]

Generally, cooling issues are only down to 2 things.

1) coolant cannot be cooled because the rad is missing half its fins or is clogged.
2) coolant isn't flowing (because either the water pump is nackered, air in system caused by a leak, sticky thermostat, etc).

Generally, I find there is no need to use the bleed nipple. After any drain/refill, simply massage the large pipes and you can burp most of the air out of the system with the rad cap off, then run it with the rad cap off, then let it cool, top it up and usually your done (one finaly top up the next day after its got to full temp and cooled down overnight).

Overheating generally doesn't tend to be electronic related. Only the fan switch is used to control the rad fans, the other 2 are for the gauge and the ECU which do not control the additional cooling. The AC fan may not activate since you have your AC rad removed from the other post - if there is no pressure in the system, the system will most likely not activate, including the ac fan). If you still have them, your better off with the genuine OE sensors rather than replacements (unless they are OE), but generally I don't believe they need replacing ever.

I presume you have already:

1) flushed the entire cooling system cold with a hose pipe and the heater matrix, then run it on some water and special cooling flush agent for a few journeys, then replace with the correct antifreeze mix.
2) Check physically the rad (either by removing, or with a torch) that the fins are all in tact and firmly in place (give them a gentle prod). at face value some rads can look fine. Its only in the light of day outside the engine bay you see they are actually totally shot.

If all that tests good, the next most common item is the thermostat itself or the rad cap, they can't be much so make sure you replace it with a known good one of the correct rating. You should be able to get a genuine honda one for not much. use AMAYAMA.COM to get the right part number.

If after flushing/refilling/new thermostat/checked rad is all good, then you most likely have a flow issue. Worth checking the overflow tank spill off pipe isn't blocked, and give the tank a good clean out also whilst your there. Flow issues can be caused by water pump impeller rusting away or coming off its spindle (unlikely in this car), or problems with flow caused by head gasket issues (also rare, but given age and mileage of cars now, if all else checks out this could be a possibility, but generally the car will not cool down once it starts to overheat in my experience of this).

a few questions:

1) Is the car lowered at all? Any other work done recently? Still got your undertray?
2) has anyone used any stop leak or similar additive to the coolant?
3) where did you get the thermostat housing / thermostat from?

Generally we get very few overheating posts on here. I've only seen it once on my car in the dead of summer when pushed very hard (and even then its only just above half way).

[Jackthelemming]

Thanks for the reply!

I haven’t flushed it nor used any additives I just topped up the coolant replacing what was lost when removing thermostat - but I did actually find it was much easier to not use the nipple at all! Originally my temp gauge wasn’t working until I changed the sensor.
That’s interesting about the AC, I will probably get a condenser for it and take it from there but does the ac fan automatically come on when the engine cooling fan comes on?
Not lowered, still have undertray and no recent work done except by myself replacing the sensors and the thermostat which came off a prelude with the same engine.
I think it’s probably my radiator - it’s been steaming a bit but i just assumed that was the coolant from where I had spilt some? I bought a new thermostat before I bought the housing but I haven’t changed it - I’ve been to two places for a new thermostat but I took the first one back because it was smaller than the oem one so I looked elsewhere. When I was sent the same size again I assumed it would work, but I have not put it in yet as I’m unsure if I can use this one still?

[Scott560]

That’s interesting about the AC, I will probably get a condenser for it and take it from there but does the ac fan automatically come on when the engine cooling fan comes on?

I believe so, overheat is bad, so both fans are best. For AC, only one fan blows for quietness i believe.

I think it’s probably my radiator - it’s been steaming a bit but i just assumed that was the coolant from where I had spilt some?

Its normal for a bit of steam if you've been pouring and doing work etc. If you've driven it up to temp and back home and its still doing it, its probably a leak. The problem with small leaks is the super hot fluid evaporates off and doesn't leave much of a trace. I find using the green antifreeze in highest concentration will help show the leaks through the coloured dye it leaves behind (also, if you go over 40% mix, the liquid becomes very thin and will leak much more easily than lower concentration, it also holds less heat ironically). If you were overheating due to a leak, you should have noticed a drop in level by now. However, it takes a few heat up and cool downs to completely expel all air in the system and for the level to settle in the expansion tank. When the car cools and the coolant shrinks, it should suck it back out of the expansion tank, but you can get air in the pipe and all sorts so it takes a few journeys and cool downs to absolutely understand the level. Top up from the rad right to the top if you have to refill (not in the expansion tank, although keep that topped up too).

Regarding the thermostat, some parts on hondas just never go wrong, so they are not well catered for in the aftermarket. In these cases, you are just better off going straight to Honda for official OEM part. Ok it might be a fraction more expensive, but the assurance of quality and OE fitment are worth the £10 or £20 premium (if at all, some parts are surprisingly the same price as random linglong dingdong parts), especially when you have to re-do work and replenish expensive fluids.

For my car at least, 2000 year, h22a8 VTi, this is the page:

https://www.amayama.com/en/genuine-cata ... ne/E__1500

There is a different thermostat housing for the F series engine, hence the confusion over parts I suspect (shown bottom left of the image, the numbered items do not highlight the parts list on the right).

You can then search ebay/internet for the part number (strangely, 2 are listed with no explanation) 19301P13305 and 19301P13306 (more often stylised 19301-P13-305 and 19301-P13-306)

Some thermostats also come in a range of temperatures for differing climates, so buying parts on line, this information can sometimes get lost.

From the service manual:

Screenshot 2024-08-09 182034.png

testing thermostat:

Screenshot 2024-08-09 182234.png

Normally the temperature is stamped onto the bottom of the brass bulb, but in this case it doesn't say what it would actually be rated at...


One other part I wouldn't have expected, bleed/toggle valve/pin should be at the top to help air get past:

Screenshot 2024-08-09 182348.png

I think I replaced my rad cap as a matter of course - worth checking it visually on the seal, and that the spring loaded part moves freely and isn't seized, this is crucial for maintaining temperature and level in the system.

[Vtecmec]

Once you've run the car up to temp and let it cool back down, where is the level in the expansion bottle? Most likely you've still got air in the system.

[Jackthelemming]

The level is full on the bottle and I’ve had it up to temp a few times topping it up until it wouldn’t take anymore. Think it’s probably the rad so gonna replace that and take it from there!

[Vtecmec]

Does the expansion bottle level rise with a warm engine and drop back down when it cools off?

[RattyMcClelland]

With the Lude, jack up the front drivers side as far as you can and then bleed the coolant squeezing the top and bottom hoses. Then take it for a drive and repeat the process again. Always get an airlock when I think I've sussed it.

[wurlycorner]

Generally, I find there is no need to use the bleed nipple. After any drain/refill, simply massage the large pipes and you can burp most of the air out of the system with the rad cap off,

You've been lucky then - they're normally an arse to get the air properly out of!

To clarify - both of the fans engage for about 15 seconds when the car is idling hot and the temperature does drop very slightly but not to the correct temperature.

That's about normal they should only need to run for that long when idling hot, to bring it down to temp - that indicates that cooling system is working ok and that the car thinks it's running the coolant at the right temperature (else it wouldn't switch the fans off). That suggests a gauge/indication issue rather than anything else - yet you say you've changed the sensor that runs the gauge. Question: does the gauge show the same problem as before you changed the sensor for the gauge, or does it show a different problem?

A few more questions:
What rad cap are you running on the rad?
Did the car previously run ok and this problem just started 'recently'?
Was any work done before the problem reared its head or did it just appear of its own accord?
And just to check - there's no sign of the coolant and oil mixing, is there? (oil isn't milky inside the oil filler cap/rocker cover/on the dipstick etc.?)

[Scott560]

I find the best way is to fill the rad up to the absolute max.

Squeeze with 2 hands, the large rubber pipe going over the gearbox, you'll lose a little coolant, but hopefully air will come out mostly.

If you do this slowly, eventually you will make more space than you spilt. I think the trick is to release your squeeze slowly. This will allow the system to backfill through that tiny little toggle valve in the thermostat housing.

It takes a good 10 mins of squeezing/releasing/refilling, but you can normally burp all of the air out of the system. I've never had to touch the bleed screw on either prelude (and they both had coolant flushes at least once). I use 40% antifreeze mix which is very thin.

Helps to run the car up from cold also, with the cap off whilst doing a bit of the squeezing, only for a minute or so, then put the cap on - eventually you should be able to feel that the lower pipe is completely full. Once its a warmed up a bit and the top rad hose has some heat in it , you can let it cool down and then top up the level. That's all i've ever needed, its a slight faff but having snapped off more than enough bleed nipples/valves in my time, i take the slow and steady approach these days (Still end up breaking something lol).