Intercooler understanding

MikeT · Post by **MikeT** » 26 Jun 2007, 10:47

Please correct me if I'm wrong but from my understanding, an intercooler is a radiator for the hot compressed inlet gases.

If the intercooler was leaking, would there be any indication?

Before I tightened all jubilee clips, I noticed oily drips would seep from the inlet joints, indicating the presence of oil (from the breather?) in the air inlet ducting.

Is this bad for the engine? If so, can the breather be baffled better to stop it's ingress into the ducting?

Is it possible this oil could also enter the intercooler? What are the implications of this? Thanks, Mike

Post by **RichardW** » 26 Jun 2007, 11:04

"Please correct me if I'm wrong but from my understanding, an intercooler is a radiator for the hot compressed inlet gases. "

No correction required, that's correct

"If the intercooler was leaking, would there be any indication? "

It would probably whistle, and performance might be down

"Before I tightened all jubilee clips, I noticed oily drips would seep from the inlet joints, indicating the presence of oil (from the breather?) in the air inlet ducting. "

Normal - you get oil from the crank breather and also sometimes a bit weeps from the turbo seals

"Is this bad for the engine? If so, can the breather be baffled better to stop it's ingress into the ducting? "

No and no

"Is it possible this oil could also enter the intercooler? What are the implications of this?"

Yes; none - it's normal. Providing the engine is not breathing too much and causing oil burning problems, I'd say everything was normal on your car. 8)

MikeT · Post by **MikeT** » 26 Jun 2007, 14:11

Thanks for the reassurances RichardW

steelcityuk · Post by **steelcityuk** » 27 Jun 2007, 08:51

Some manufacturers recommend flushing out the intercooler at high mileage to clean out the gunk and bring it back to 'full' efficiency. I did this on the 405 TD I had. I used paraffin and allowed it to drain thoroughly.

Steve.

jeremy · Post by **jeremy** » 27 Jun 2007, 09:09

Steve - as you make no comment can we assume that flushing your 405 intercooler made no difference?

Just a word of caution - solvent left in the intercooler after flushing could wreck your engine.

Post by **CitroJim** » 27 Jun 2007, 10:01

jeremy wrote: Just a word of caution - solvent left in the intercooler after flushing could wreck your engine.

I guess if you wanted to do this, the best stuff to use would be diesel?

If there was a lot of liquid of any description left in the intercooler I presume mechanical damage to the turbo impeller could be caused as well as a risk of the engine overspeeding from running on a source of unmetered fuel.

MikeT · Post by **MikeT** » 27 Jun 2007, 10:54

steelcityuk wrote:Some manufacturers recommend flushing out the intercooler at high mileage to clean out the gunk and bring it back to 'full' efficiency. I did this on the 405 TD I had. I used paraffin and allowed it to drain thoroughly.

Indeed, the Haynes BOL states that failing turbo seals will allow oil into the intercooler and it should therefore be flushed with solvent. I'm wondering what effect an oily intercooler has on performance and reliability and how bad it can get if left unchecked.

Post by **CitroJim** » 27 Jun 2007, 11:19

MikeT wrote: I'm wondering what effect an oily intercooler has on performance and reliability and how bad it can get if left unchecked.

Quite significantly on performance Mike. If the intercooler is internally blocked this will reduce airflow through it and reduce efficiency by lowering effective boost. The boot generated is dissipated in trying to blow through a partially clogged intercooler.

The intercooler can also suffer if it has not got a clear external airflow through it. Xanta Intercoolers are terrible for getting all sorts of bebris trapped between them, the coolant rad and the A/C condenser, even dead birds. So do check that aspect.

Take the intercooler out (the coolant rad will have to come out too) and tip it and see if any liquid oil runs out. Going on what you say about the BoL, if the Turbo seals were iffy, you'd be seeing blue smoke out of the exhaust before the intercooler got really contaminated, I would have thought. Normally there is a light oil mist passing through it from the engine crankcase breather.

A good demo of how much a good intercooler helps a TD is to drive a 405 with the top mounted one. Stop in traffic on a hot day with a hot engine and the intercooler will suffer heat-soak as it absorbs a lot of engine heat. The engine will not then pull your hat off until the intercooler is once again cooled by moving air. Xantias with the front mounted one don't suffer quite as badly but the effect can still be felt. Shows the importance of keeping it clean and clear of external dirt and debris.

jeremy · Post by **jeremy** » 27 Jun 2007, 11:32

As Jim has said the purpose of the thing is to cool the charge - so ideally you want contact between the air and clean metal. Oil is not a particularly good conductor of heat so the metal/oil and oil /air junctions as well as the oil itself will reduce its efficiency - but I've never heard of anyone improving things by fitting decent oil traps.

The problem with solvent will be getting it all out. I suppose a high volume low pressure air source would be best - but who has one of those. The problem with simply blowing it out is that the air will probably take the shortest route and not reach the corners - so solvent lurks until full boost is achieved.

steelcityuk · Post by **steelcityuk** » 27 Jun 2007, 13:19

As noted in my post I used paraffin which being very close to diesel is a good solvent to use, also drained THOROUGHLY, it should also be noted that due to the way intercoolers work they don't have to be blocked to reduce their efficiency, it's not just airflow that matters it's heat transfere so if the insides are coated with gunk it will reduce the intercoolers efficiency. Yes it worked very well. The gunk that came out of it was unbelievable. I did it at the same time as I changed the cambelt, water pump, 2 tensioners, flushed the rad, etc. Would some like to find fault with that too? Far too pedantic at times forums.

Steve.

Post by **CitroJim** » 27 Jun 2007, 13:54

Excellent Steve

steelcityuk wrote: Would some like to find fault with that too? Far too pedantic at times forums.

No finding fault, simply lively debate to tease out all the points

You think this forum is pedantic. Try some others. This one is really quite gentle...

MikeT · Post by **MikeT** » 27 Jun 2007, 14:56

I did wonder about the breather mist too... so even with sound turbo oil seals, there will be gunk going into the intercooler

and from what you're all saying, it's detrimental and mine probably needs to be cleaned. Paraffin sounds like an ideal solvent to use in this case

I did hinge the rad forward and saw a little bit of debris between, nothing drastic. But I thought there was just the rad and then intercooler. Where does the condensor live exactly?

Post by **CitroJim** » 27 Jun 2007, 15:07

MikeT wrote: Where does the condensor live exactly?

just behind the intercooler Mike,

The rad, intercooler and condenser make up a sandwich.

MikeT · Post by **MikeT** » 27 Jun 2007, 15:13

So the double fans I see through the grill are attached to the condensor, not the intercooler as I presumed?.... I see....

Sandwich indeed! Frontal collisions must be comparatively costly then.

That's why they put the handbrake on the front wheels... to stop any fast thinkers from broadsiding unavoidable accidents.

Post by **admiral51** » 27 Jun 2007, 15:37

mike t wrote

So the double fans I see through the grill are attached to the condensor, not the intercooler as I presumed?.... I see....

i had to replace the complete fan housing as it was well and truly shot on my 1.9d xantia
had bumper and slam panel off to gain access but had an awful lot of crud between condensor and rad.
condensoer was real grimy/dusty needed a wash off with light hose pressure.
rad/intercooler/condensor will sit on bottom lip of fan housing and be extra careful if moving condensor- pipes in a block l/h bottom of condensor as you look from outside very expensive to replace and held into fan housing by a couple of PITA screws- allen key heads on mine
colin