Why prone to overheating?

[nominous]

I keep reading threads about overheating and blown HG's, so it seems it's just "the thing" to repeatedly fix on the XUD's.

But why ?
What makes the engines prone to overheating?
Is it a build up of crud in the water galleries that you cannot clean out?
Pump worn or over speed so cavitation?
The air lock issue when filling & air getting in somehow over time?

Anyone tried Evans coolants ? Supposed to be good for especially localized heat spots (I haven't I haven't had a problem with this)

Just not looking forward to modifying then having to keep doing HG's or a special eye on temps.
I won't be able to run a constant flow cockpit heater/radiator either, so more concerning (but have read about flow restrictions to overcome that).

[Danny2009]

Headgaskets are the main culprit of over heating
They use a fiber gasket from factory and these engines are 12 years old if not older

If it goes replace it with a multi layer steel (MLS) gasket and have head skimmed ect and you should have any more issues

[ozonehostile]

The inefficiency of indirect injection technology is the main culprit...

Chronic amounts of heat produced for very little gains compared to direct injection

[Ruan]

XUDs have a bad reputation due to people not being able to follow simple instructions and motorfactors supplying incorrect parts, looking for a quick buck.

They were supplied from the factory with multi layer steel headgaskets, PSA recommended that the coolant be changed every few years or so (fair enough, ally head, steel block, good practice) and garages didn't bleed them correctly due to the header tank being lower than the level of the bleed points (they didn't follow the manual that would have said to make it higher than the bleed points, or pressure bleed it), then gave it back to the customer who didn't notice the temperature gauge pinging off the "f*cking hot" mark, drove it back to the garage with no water, warped the head... Then the garage changes the head gasket, because it's guaranteed to be blown after getting that hot...With some shitty fibre gasket from the motorfactor, doesn't skim the head to keep costs down, then it's just a recipe for the gasket going AGAIN!

They are quite sensitive to heat, if you allow them to get hot, they will start blowing gaskets, that's just the joys of having an ally head on a steel block with precombustion chambers - they put an incredible amount of heat into the cylinder head and have to be kept cool, if you don't keep it cool, it'll just warp the head and blow the gasket, the localised heating is so intense. They don't give the same instant obvious issues of a petrol with no water in, i.e. power dropping off, instant boiling over of the coolant... That all happens with such vigor... An XUD will plod along, with water boiled off in the cylinder head, airlocked to shit, with no cooling, but won't spray everything out the header tank, but by that time it's too late and you've f*cked the head gasket.

The real problem is that people assume the temperature gauge is just a reading of how hot the entire engine is, not an average thing - if the engine was actually still filled with coolant around all of the bits in the head when the gauge is reading 100*C and not boiled off, it would actually run fine, it's just that generally if the gauge is reading 100*C then there is a serious problem and it'll have boiled off the coolant - meaning that probably inside the head it's coming on 150*C with essentially no cooling, but the gauge is happily reading an average of 100*C...

Also people driving round with corroded radiators doesn't help at all, the stock radiators do corrode out - essentially they end up driving round with no cooling system.

I've had an XUD for ~ 6 years now, I've never *blown* a head gasket, I've stretched head studs, had coolant blowing out the header tank, but never actually destroyed the gasket as such, every time you retighten the studs, it's fine again... Essentially an XUD is unbreakable if you don't overheat it.

TL;DR: Do not let them get hot, they don't give much warning and are a bit sensitive to people who assume they're unbreakable.

[welshpug]

yeah, that.

not prone at all, just old and neglected.

[nominous]

Fair game. RTFM advised
Thanks for the info folks.

I was thinking about CHT's as well as EGT and manifold pressures. More monitoring is usually better than less.
Especially if you run it into an arduino or something to get a warning rather than monitoring gauges as the sensors are dirty cheap just the gauges that get pricey, and a mate of mine is building a multi-channel EGT monitor.

Is the stock temp sensor in the head or the block ?


Speaking of incorrectly following guides, I got a CRX from a Honda dealer once with a suspect "broken head" due to snapped timing belt.
Turned out they hadn't followed the Honda workshop manual when fitting the new belt, else they'd have diagnosed a seized Distributor.
Luckily I had one on the shelf. Just wish I'd fitted it at the dealer and driven away

[Paul Baldwin]

Ruan's pretty comprehensively covered that! Especially agree with the rotting rads point, they always end up leaking in the bottom corner or thereabouts. That's been the end of many a 306 and ZX after a half arsed repair and then people weigh them in when they fail again soon afterwards.
If you look after the coolant system they tend to look after you pretty well. My mothers 306 is testament to that with 250,000 miles on it and counting
Even with the gasket gone they can keep going for ages. A mates been running his over 7 months now. He's just drilled a few holes in the rad cap to release the pressure and tops up regularly.

[Ruan]

Fair game. RTFM advised
Thanks for the info folks.

I was thinking about CHT's as well as EGT and manifold pressures. More monitoring is usually better than less.
Especially if you run it into an arduino or something to get a warning rather than monitoring gauges as the sensors are dirty cheap just the gauges that get pricey, and a mate of mine is building a multi-channel EGT monitor.

Is the stock temp sensor in the head or the block ?

Be warned of using an Arduino for accurate temperature measurement - you have to be very conscious of ground reference points - if you assume that the entire electrical system is a good common ground, you're going to get massively funky readings - you have to really have well shielded wires using their own seperate ground and good filtering on the power circuit... Problem being that the electrical system deals with hundreds of amps and fairly crude uncontrolled 6-pulse bridge rectifier with very little filtering - meaning that you get quite a bit of ripple, not to mention the other stuff that's on the electrical system!

The stock temperature sensor is in the thermostat housing after all the coolant has been round the block... Meaning if there's nothing in the head, there can still be water happily coming out the block waterways.

You may be best off placing another sensor in the actual waterways in the cylinder head - infact a great way of seeing if the head is aired is to keep the heaters blowing hot at your hands - that way when they go cold, you know it's got air in and to pull over immediately!

[jammapic]

Just my 2p, and it goes with what these guys have said.

I ran my XUD at 180+hp! sometimes over 200hp with very little cooling problems for 2 years.

The key is, to KEEP it cool, and as Ruan says, not to overheat it.

I found that with the stock rad, and oil cooler, it would get hot straight away pretty much. I then found the rad was old and knackered, so replaced it with a nissens one.. Better, but still overheated.

No chance of doing 5 minutes of full on track time, let alone a full 15 minute session.

I then decided to spend some money, and had a huge 4 core, 10l radiator custom made, and rebuilt the front end with a 16 row oil cooler.

This was waaaayyy better. Could do a full 15 minute session without the temperature even coming up from the 80c mark.

As the guys have said, indirect injection engines makes heat... Simple as. The stock cooling system in good form can just about keep a 90hp xud cool for sustained periods of foot to the floor, but throw in more fuel, more boost and an intercooler partially blocking the rad, along with crusty old radiators and it's a recipe for disaster.

As Ruan said, a decent, fresh cooling system, with decent coolant and some mechanical sympathy should be right enough, but drive it like a tool and you will overheat the head.... Then bye bye gasket.

If you want to do long, sustained periods of high power outputs, you really need to be looking at oil coolers (to take some heat away from the water cooler), and a bigger rad. This, completely, cures XUD overheating and you can give it full whack on a track, for 15 minutes at a time and it'll be fine.

The last thing to watch is EGT. I made sure my car didn't smoke too much under full load, and with the above mods it never overheated and NEVER did a gasket.

Maybe I wasn't trying hard enough

JP

[Daniel306]

I found that at 110* the head will warp, was regular to see 100* and survive. I just needed to learn to watch the gauge


Iv got a 307 136 hdi, just had a new radiator but when the trailer is on it sits about 90-100* what is safe on the Hdi?

[jammapic]

I've never seen a hdi go over about 85c tbh...

[Toms306]

My estate hit 100c while the rad cap was off (didn't want to pressurise the system due to the broken sensor housing), Id guess you're losing pressure somewhere Dan. Either that or your fans aren't coming on, but I can't think of the last time I had fans come on in the HDi while stationary let alone while driving lol.

[Daniel306]

Never seen the fans on either, im sure there was some setting in PP that said twin fans when my car only has a large single fitted. this engine is a 2.0 16v but im sure it should not get that hot

[nominous]

Ruan, I don't know the specifics (just saying ardunio as it's common speak, like Dyson for a hoover ) but that will certainly be covered. Taking a leaf outta Honda's ECU wiring, all the signals are shielded and the whole engine management system is referenced to one ground on the engine block. Every time I've done ECU interfacing, I always do power and GND from the ECU (such as widebands or real time programmers). Power would be switch mode and some big caps, not just a linear reg.

Good point on the bigger rad. I'm doing something similar having chopped the front panel off on a Honda and using the whole space to fit IC and rads which will take on the job of being the slam panel and bumper mounts too.

It's never going on a track (never say never) just spirited driving and mainly motorway slogging at 3rd lane speeds.