Coolant problems, the sequel. FFS..

[roadboy]

I haven't met anyone who put a Honda in then had no issues....

Dan@JPS

[mckeann]

I haven't met anyone who put a Honda in then had no issues....

Dan@JPS

On your car maybe, but surely some of your customers must have had teething problems

[roadboy]

I didn't say that I hadn't had any problems with any of the conversions I have carried out. Read Cambell's quote again.

Dan@JPS

[tut]

It actually reads that everybody has had issues with Honda conversions.

However virtually none of them have been with the engine or gearbox, which are virtually bullet proof as long as you change the oil now and again, but driveshafts and CV joints have been a PITA, as have brake discs unless you pay more than I can justify for oversized AP racing ones.

tut

[fd]

The car is only as reliable as the weakest link, so the reliability of the engine is irrelevant if the driveshafts are continual failure items . . . how many driveshaft failures he you had in how many miles Tut ?

Fd

[tut]

Two snapped early driveshafts on N1 Fergus and around four CV joints. Would have been less without the Sprint and Hillclimb standing starts, and the tyre warming that I later gave up was lethal to the drive train. That was in around 50,000 miles. Plus one clutch.

Not sure of the total mileage on N3 since it was converted, but I have done around 15K in the past year. No driveshafts so far, but an outer CV and an inner tripod joint have gone.

Fairly confident of the driveshafts now, and hopefully the left side as that has just had a complete upgraded Sinclaire assembly fitted, but a CV joint on the right side will probably be the next to go.

tut

[roadboy]

It actually reads that everybody has had issues with Honda conversions.

Yes it does Tut and I was simply stating that in the numerous trackdays and several thousand road miles that mine has covered since the conversion I have not had a single issue.

I think it would be interesting to compare how many K-series cars putting out the same power/torque as the Honda, being used in the same circumstances, have had CV issues.

I'm not a Honda fanboy by any stretch of the imagination so not sticking up for the conversions here, just trying to put it into perspective.

From a personal perspective my car has been no more or less reliable with the Honda in than it was with the K-series in, its just a hell of a lot faster and nicer to drive.

Dan@JPS

[robin]

Anyway, let's stay on topic and try and get the K sorted, unless John is seriously thinking about the Honda conversion as a fix, in which case fair enough, it's on topic

Or is this just a moaning session, in which case I'll move it to general drivel^h^h^h^h^h chat and be done with it

Happy Easter all

Robin

[Victor Meldrew]

Anyway, let's stay on topic and try and get the K sorted, unless John is seriously thinking about the Honda conversion as a fix, in which case fair enough, it's on topic

Or is this just a moaning session, in which case I'll move it to general drivel^h^h^h^h^h chat and be done with it

Happy Easter all

Robin

If I ever do an engine swap... it wont be a Honda ... Dan knows what I am thinking about.. would be the first in Scotland if I did go for it...

But as the budget doesnt stretch that far for now.... (it only just about streaches to a rebuild.....) the engine swap will have to wait.

[Mike Scib]

If I ever do an engine swap... it wont be a Honda ... Dan knows what I am thinking about.. would be the first in Scotland if I did go for it...

But as the budget doesnt stretch that far for now.... (it only just about streaches to a rebuild.....) the engine swap will have to wait.

You could always by my S3

[Victor Meldrew]

Done the fast Audi. I had an S6 for seven years.

Just want to get the car running for Donny and I can worry about a donor engine later in the year.

Will need to get a better understanding of the engine regs before I dive in and end up with one that 20cc to big for my chosen class.

[BiggestNizzy]

Engine swop ?

kaboom

[robin]

Fair enough. So do you have any answers for the questions in my earlier post? If you're just posting to keep us up to date with what's happening to the car, you don't need this thread in technical any more I think?

Cheers,
Robin

[Victor Meldrew]

BTW, you can achieve a similar load on the engine by keeping the left foot on the brake whilst the right foot is flat on the accelerator. Just do it somewhere sensible (empty motorway) - it means you can keep the tuts the right side of 90

But what actually happens? I assume you're seeing high temperatures on the dash, but what else? Does the expansion tank blow its lid/vent steam, is the radiator actually hot when you pull over? After the event is there any gas in the cooling system that needs to be bled out?

The car temp normally sits about 87-89deg The first indicator is a rise in temp about 5mins before it kicks off properly, up to about 95-97. The temp then starts to climb rapidly to about 107. When the temp goes over the 100deg, you can smell the coolant venting from the header tank (confirmed when you stop) the radiator is cold at this point...

If you pull over and leave the engine running, does the temperature return to normal, or does it keep rising/stay very high.
If you leave it running it climbs to 120 and stays there...

If it does return to normal on the idle, what about if you pull over, but keep the engine revving at say 3,000 RPM?
Never had the bottle to keep the revs up....

Do you know for sure that it's not just a dodgy temperature sensor/wire to the dash? Have you verified >100C temperature at the coolant elbow using a IR thermometer or thermocouple thingmy? When it overheats and you pull over, while the dash is showing >100C temperatures, is the radiator fan running?
The fan runs when its showing over 100.


Have you measured the temperature across the radiator immediately after it fails?
Never had the digitherm in the car with me when its failed...but its cold to the touch.

I cannot help but think that rather than Dan ripping it to pieces again, it would be more fruitful to have you test drive it at Dan's, break it, pull over, Dan jumps out and checks the temperature in various places with the thermometer; indeed with a willing accomplice that could have been done here and saved Dan another trip.
Well Dan has the car just now... and I am sure he will try to re-create it himself before he rips it to pieces...... but he did put over 300miles on it without re-occurance..

There are, as I see it, only three root causes of the overheating:

(1) The engine is gassing into the coolant, which would probably be combustion gasses; there is a theoretical possibility of the opposite - coolant->engine with no reverse flow of gas. Either way, the cooling system could then lose pressure and boil; it'll take a while to return to normal. If the engine->coolant case you would expect a block check to show up HC in the expansion tank. In the (hypothetical) coolant->engine case you would expect the coolant level to drop after each event.

The head was off and pressure tested, all ok.. I dont know if he has done a sniffer test.. So its either the head or the liners in this scenario? The head has been checked in a heated bath. The liners looked in good condition.... There has been no water detected in the oil at any time, so its re-do the sniffer test and take it from there.. the coolant drops but I was putting that down to the cap venting loads all over the deck. I have tried more than one cap. At rest the car idles the temp rises and falls with the fan kicking in/out as any other normal car would with no loss through the cap or any visible leaks anywhere

(2) The coolant flow is not travelling through the radiator. This can be because there is an easier path (e.g. the run through the heater matrix or bypass type circuits is easier than the run through the radiator), or because the stat is blocking the egress from the radiator or because the pump is no longer pumping coolant.

The car has a PRT fitted. This is what we thought was causing the problems initially. The PRT has been out and bench tested. A restrictor has been fitted on the bypass loop to assist the flow to go through the radiator.

(3) There is nothing wrong with the system at all and it's just a dodgy coolant temperature sensor.
Oh I think we say for sure that there is still something wrong...

I'm pretty sure you've ruled out (1) by now, as it's what we would all suspect first!

We thought that we had ruled that out with a pressure test on the head.. possibly not.. [/i]

[robin]

Excellent data, ta.

So, we know the engine really is getting hot - it's not just an electrical fault (the fan wouldn't run in this case).

The fact that the radiator is stone cold when the engine is 100+ is pretty indicative of a thermostat or coolant circulation problem, rather than a head/block problem.

If the pump had failed then you would see no flow back into the header tank either.

Airlocks in the radiator are a possibility but that would probably be caused by gassing into the coolant (by now the system has been bled a lot, so any trapped air would surely have come out); also airlocks tend to cause problems at low revs; at high revs they are usually overcome by the pressure differential across the radiator.

A blocked radiator could be an issue, but then you would find no flow through it on idle either. I'm guessing the system heats up and works normally when not thrashed to death?

It seems to me that the thermostat is the most likely cause of these symptoms.

The PRT operates using both temperature and pressure. There are three pipes - the one from the rad, the one from the bypass and the one to the pump inlet.

The radiator return feeds the backside of the stat (this comes from the alloy pipe on the pax side chassis rail). Exactly opposite it, the bypass feeds the front side of the stat (this comes from the coolant elbow on the head). At an acute angle to the bypass, there is a pipe that feeds back to the original thermostat housing to allow the coolant back into the engine.

The main chamber acts like a mixing pot, blending together hot and cold coolant from the bypass and the radiator. The stat has a valve at each end and slides back and forth; i.e. it opens at one flow as it closes off the other. The stat is measuring the temperature of the coolant in the chamber; too hot and the stat shuffles across a bit to allow in more flow from the radiator and less through the bypass; too cold and it shuffles the other way to allow more flow through the bypass and less through the rad. But it has an extra trick; when the pressure differential between the bypass and the oulet increases, the valve that closes the bypass opens again, even if the stat is shuffled across to open up flow from the rad and close flow through the bypass. This mechanism works alongside the wider pipework in the bypass to make the pump work better at higher speeds (on the normal setup, the pump just creates a big pressure differential; on the PRT, it spins loads off coolant through the bypass loop).

In the end, the temperature regulation side of the stat is supposed to dominate the pressure relief function. So when temp reaches nearly 100C, the stat will shuffle so far over towards the bypass side, that even the extra opening allowed by the pressure relief valve doesn't allow any flow through the bypass.

Now, I'm assuming your PRT is plumbed in as described above (awaits correction from Dan if I've got the wrong pipes connected to the wrong ports on the stat housing!).

I can see there could be some failure modes that you can only induce by nailing it from very cold or very hot - perhaps this is the difference between your testing and Dan's?

It's also pretty clear that if you plumb it in any other way, the system will behave somewhat strangely, though it might actually work!

Finally, the system does rely on flow through the bypass being the primary bypass. If you restrict it, or if there is another bypass that is easier to flow through then the whole thing will not work properly.

Cheers,
Robin