Peugeot 106 GTI Low Compression Causes

[Locke]

For the past 3 weeks or so my 106 GTi has been making a knocking noise on idle which could be heard most from underneath the car from around the sump area and a very slight rattle at low rpm, it did drive fine though and didn't feel to be lacking in power.

A couple of days ago I was going along and within the space of a few hundred yards my engine started to sound horrible and I felt a severe loss in power at this time so I pulled over, My water temp wasn't hot (below half way) so I didn't think it was the head gasket.

I drove the car home as it did run but was misfiring really badly (it had such little power I couldn't use 4th gear even on flat)

I was hoping it was just a faulty coil pack or spark plugs but I changed both of them and it made no difference.

The other night I did a compression test and the readings that I got were: 55, 55, 210, and 210 (from left to right)

So what I’m now wondering is...

What has caused this? Could it be head gasket failure even though I drove my car 8 miles home without it over-heating?

Could the knocking I was experiencing prior to this be linked to what’s happened now?

Basically what do you thinks happened if you were to have guess?

I would have posted this in the French Bred section but you get very little replys.

Thanks in advance.

[Locke]

PHuzzy said:

The 16v engine works on a wasted spark ignition system, it fires two cylinders at a time but still sparks the other two. Which would lead me to believe an ignition problem of sorts.
You could also assume with such a low compression on two cylinders it could well be a valve problem?
I take it your engine management light is on? Best bet is run it through diagnostic check to find your answer, although it could be less than helpful and say misfire on cylinder 1&2!

A list of things that I'm only guessing on could be:
Crank bearing(s)
Electrical Fault
Dodgy plugs
Bent valve(s)
HGF

I'll leave the floor open to some other PHers to pull apart or confirm my guesses.

Surprisingly I have no warning lights on my dash which I can't understand. I changed my spark plugs and borrowed a friends coil pack which made no difference at all.

Could an electrical fault cause low compression? I though I'd pretty much ruled out it being anything electrical.

[Locke]

JimGTxx said:

shalmaneser said:

Low compression is either going to be...

Valves not seated right
Head gasket
knackered rings.

Given that two cylinders next to each other have gone, HG seems the likely culprit.

Either way you'll have to pull the head to find out. Get the spanners out.

However, this still leaves you with a potentially fked bottom end, might be easier just to drop a new block in.

Unfortunately, what he said.

Drain the coolant out, drain the oil out, pull the head off and inspect, drop the sump off and inspect.
replace and rebuild as necessary.
Do you know what to look for on the cyl head and gasket? Do you know how to check the main and big end bearing, crank journals etc?

No, what do i look out for? I got told to look out for glitter in the oil as this would indicate shaved bearings. Is this correct?

[Locke]

Locke said:

JimGTxx said:

shalmaneser said:

Low compression is either going to be...

Valves not seated right
Head gasket
knackered rings.

Given that two cylinders next to each other have gone, HG seems the likely culprit.

Either way you'll have to pull the head to find out. Get the spanners out.

However, this still leaves you with a potentially fked bottom end, might be easier just to drop a new block in.

Unfortunately, what he said.

Drain the coolant out, drain the oil out, pull the head off and inspect, drop the sump off and inspect.
replace and rebuild as necessary.
Do you know what to look for on the cyl head and gasket? Do you know how to check the main and big end bearing, crank journals etc?

No, what do i look out for? I got told to look out for glitter in the oil as this would indicate shaved bearings. Is this correct?

How do I spot a fked bottom end?

[Locke]

Kitchski said:

Just checked your profile.....long way from me! Go to a local decent garage that have a leak-down tester first. See if you can highlight exactly where your wasted compression is going!

Ok thanks, I didn't think the knocking I was experiencing prior to my HGF was linked but just wanted an idea of what the knocking might be as it would be a waste to spend money on a new head gasket if I have a fked bottom end.

My engine would only knocked when warm whilst on idle it never did it on start up and the knocking didn't get faster when reved. Its a really tricky one.

I could somtimes here a very slight noise when driving along at a low rpm that sounded similar to a heat sheld vibrating but it wasn't because I checked and double checked and found nothing to be lose. It seemed to do this more when going up hills aswell. It was making this noise slighly louder than usual right before my HG failure also.

Edited by Locke on Saturday 22 January 01:46

[Locke]

oakdale said:

Why are you worrying about the crank bearings?

You've got low compressions on two adjacent cylinders most likely caused by a head gasket failure, (this can cause some horrible combustion knock noises).

Whatever the cause, the head needs to come off but I haven't read anything here that suggests crankshaft or bearing failure.

Is it possible then that just simply doing the head gasket may cure some of the knocking I was experiencing prior to it going. Could the knocking I was getting before be linked to the head gasket being on it way out?

[Locke]

oakdale said:

Why are you worrying about the crank bearings?

You've got low compressions on two adjacent cylinders most likely caused by a head gasket failure, (this can cause some horrible combustion knock noises).

Whatever the cause, the head needs to come off but I haven't read anything here that suggests crankshaft or bearing failure.

Could the knocking I was experiencing the few weeks before be linked to the head gasket being on its way out then? As I was getting the knocking before I lost compression. Could it be possible that by doing the head gasket I may get rid of the knocking? Or is there a good chance it will still knock?

(I understand its hard to say as you've not heard it yourself, but thanks all the same )

Edited by Locke on Saturday 22 January 02:09

[Locke]

Old Merc said:

I`ve worked on Peugeot engines for years and have seen a number of head gaskets fail between 2&3 cylinders on this 16v Tu engine,in most cases this was due to overheating at some stage in its past?This TU is a tuff little engine and rarely gives trouble.Big ends and pistons never go,and will only fail if the engine has run short of oil.I would go for a headgasket job and have the head skimmed at a machine shop.

Thank you.