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Low Compression

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klmorrell

Original Poster:

18 posts

60 months

Tuesday 3rd October
quotequote all
Hello

This is my first post after several years of lurking, unfortunately it is a post of woe and stupidity.

3 weeks ago I set off with my Mondeo 2.5t and caravan towards Sherwood forest from near warrington. my intention was to go m6-a500 ect however the m6 was at a standstill so I ended up going over the Pennines via buxton, which was something I really didn't want to do.

Just after leaving chesterfield the car died without warning. upon opening the bonnet I discovered the expansion cap sat beside the tank, where I had forgot to put it back on after doing all my pre caravanning car checks (stupidty)

The temp gauge however never went over normal in all the journey so I had no idea of what I had done.

the car is now with a friendly mechanic who was done a compression test, using a brand new 800amp battery. he says that 4 cylinders are reading 25 and the 5th (nearest cambelt is about 45 psi. he said no water came out of the spark plug holes during the test. However the oil level has gone up over max but doesn't look contaminated.

my issue is with the value of the car, it has a trade in of £2000, retail about £4000 however its easy to say that but if no one wants to buy it then its irrelevant.

So, best case is head/head gasket = £600-£700 but my question is how likely is it that something other or as well as the head is goosed?

Thanks




GreenV8S

24,745 posts

206 months

Tuesday 3rd October
quotequote all
If the head gasket has gone sufficiently to affect the compression test by that extent then it will be easy to detect by a cylinder leakdown test. However, it does seem strange that you have had such a dramatic failure with no warning just from leaving the cooling system unpressurised, and based on what you have said so far I don't see any reason to assume that the cooling system or head gasket are what stopped the engine. They might be, but you haven't proved it yet imo.

HustleRussell

12,938 posts

82 months

Tuesday 3rd October
quotequote all
Kind of odd, Your coolant would’ve been slowly boiling off and you didn’t smell it or see any steam?

Was there any coolant in the tank by the time you stopped?

What actually caused the car to stop, did the engine simply stop running? What happened afterwards?

P.S. your compression test figures must be incorrect, either that or all of your cylinders are making a fraction of the compression that would be expected. 25psi is far too low and so is 45psi. Have you missed a ‘1’ off the front of your numbers?

Further diagnosis required.

klmorrell

Original Poster:

18 posts

60 months

Tuesday 3rd October
quotequote all
Another thing that I thought unusual at the time of engine failure was , the battery low light came on, this is on a 12mth old silver series 800amp battery that was fully charged only days before. I know it could just be coincidence that the battery also died at the same time, but never-the-less it seems strange.

i don't know how likely a head gasket is to blow across all 5 cylinders? i can imagine that the journey over the Pennines with a caravan is very strenuous on an engine and as the cap was not on then over the course of 50 miles it would of evaporated much of its water, however when opening the bonnet the expansion tank was still about a third full or 2 inches below min.

What i am trying to find out is how likely something else has gone round as regards to the bottom end ?

.

klmorrell

Original Poster:

18 posts

60 months

Tuesday 3rd October
quotequote all
The car just lost power over say a couple of hundred yards then stopped, those psi figures are correct 25 on 4 cylinders 45 on the 5th, we redid it this morning on the brand new battery.

and yes there was still water in the tank.

once home, I refilled the tank but since doing a couple of compression test the tank is now empty
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GreenV8S

24,745 posts

206 months

Tuesday 3rd October
quotequote all
klmorrell said:
those psi figures are correct 25 on 4 cylinders 45 on the 5th, we redid it this morning on the brand new battery.
Exactly how did you do the test?

Boosted LS1

16,404 posts

182 months

Tuesday 3rd October
quotequote all
Are you taking the compression reading with the throttle wide open?

HustleRussell

12,938 posts

82 months

Tuesday 3rd October
quotequote all
I imagine that engine should have a compression reading of more like 150psi or more so I have to question your method.

If the engine stopped, you have uneven compression readings and your coolant is disappearing then it is looking rather like it’s been cooked to death. Assuming the engine lost coolant and airlocked, the gasket will have blown and / or head warped and the next thing to have happened will be the pistons picking upon the bore and starting to seize, buggering the bottom end. Often the best solution if this is the case is a carefully sourced used replacement engine.

DuraAce

2,241 posts

82 months

Tuesday 3rd October
quotequote all
Explain how you are doing your testing...

Do it for all cylinders...

Cylinder leak down test would be useful. Cooling system pressure test would also show if water was getting into cylinders.

Something amiss with your methods/diagnosis IMHO...

klmorrell

Original Poster:

18 posts

60 months

Tuesday 3rd October
quotequote all
the compression test was done on wot.

I am not sure what a healthy engine should be producing in psi but I'm pretty sure it should be more than what it is atm.




TooMany2cvs

18,135 posts

48 months

Tuesday 3rd October
quotequote all
klmorrell said:
Another thing that I thought unusual at the time of engine failure was , the battery low light came on, this is on a 12mth old silver series 800amp battery that was fully charged only days before. I know it could just be coincidence that the battery also died at the same time, but never-the-less it seems strange.
It's not a "battery low" light. It's a lack-of-charging light.

If the alternator belt was covered in coolant, and the belt was slipping, then that'd do it. Or if the alternator was full of coolant...

GreenV8S

24,745 posts

206 months

Tuesday 3rd October
quotequote all
klmorrell said:
the compression test was done on wot.
That's encouraging, but you would need to give a lot more detail for anyone to confirm that the test was done correctly. From the point you opened the bonnet to the point you wrote the results down, what did you actually do?

Look at it this way: the results you're describing don't indicate the engine is knackered - they indicate it isn't an engine. Either something went spectacularly wrong in that engine with almost no warning and no major symptoms, or you measured the compression wrongly. Which it is will make a huge difference to your situation.

Also you do need to carry out the leakdown tests and cooling system pressure test that were described earlier. If the compression test results are accurate it will definitely show up in the other tests and they will give you some idea of where the damage is..

klmorrell

Original Poster:

18 posts

60 months

Tuesday 3rd October
quotequote all
I'm confident the mechanic performed the compression test correctly, I am no mechanic but I can do a compression test correctly on my old lotus, so I am happy that those readings are correct.

I helped him this morning retest the highest psi cylinder, and he showed me through the windscreen as I cranked the engine over and it was barely 50 psi.

My conundrum is, removing the head @ about £200 might not answer all the questions, realistically it is an engine out job, to check bottom end ?

this is my reason for coming here, to see how likely the bottom end is also knackered based on the info I have provided. I am already assuming the head is warped and head gasket blown.

Thank you all for your responses

GreenV8S

24,745 posts

206 months

Tuesday 3rd October
quotequote all
I don't see any direct evidence of bottom end damage in what you're described so far, but it's a definite possibility. I don't know what caused the oil level rise and that may be due to coolant in the sump, which could damage bearings throughout the engine if it went through the pump. It's also possible for overheating to lead to low oil pressure leading to bearing damage. If the bearings were damaged sufficiently to write off the engine, an experienced mechanic would probably have recognised the resulting knock during the compression test. If the engine appeared to tighten up before you switched off that might be a sign that it had hydrauliced on the coolant when you took the load off and that might have damaged a piston or rod. I don't know how easy it is to drop the sump on that engine, but if you can do that you would know for sure.

TooMany2cvs

18,135 posts

48 months

Tuesday 3rd October
quotequote all
klmorrell said:
My conundrum is, removing the head @ about £200 might not answer all the questions, realistically it is an engine out job, to check bottom end ?

this is my reason for coming here, to see how likely the bottom end is also knackered based on the info I have provided.
Is there any knocking coming from the bottom end? If not, why do you think there might be a bottom end problem?

You had cooling system issues, not lubrication system ones. Has he drained the oil yet, see how badly it got coolant-contaminated?

Pulling the head will not only show if the HG's gone, but will show any bore problems.

stevieturbo

12,647 posts

169 months

Tuesday 3rd October
quotequote all
Some clarity, as this doesnt make sense.

The car stopped on you, with no other symptoms of an issue.....if this is accurate and true, clearly it cannot of overheated.

You say the battery light had came on.....so was the batter in good order, or not.

You dont say whether the car is now dead, or what any actual symptoms are other than some water loss ?

Does it run ? Does it turn over ? How does it sound turning over ? Does it attempt to start? etc etc

As others say, those compression test numbers do not make any sense. Either the test is not being done correctly, or the gauge is faulty.

But a 40psi reading on all cylinders for a car that had no problems or symptoms whatsoever prior to an instant stoppage....is just nonsense.


klmorrell

Original Poster:

18 posts

60 months

Tuesday 3rd October
quotequote all
I think you might of missed the bit about me towing a 1.4 tonne caravan from warrington to chesterfield over the peninnes without the expansion tank cap on.

That is why I think the engine just died.,

There was no warning signs, ie the temp gauge sat on normal all the way, it didn't smell and there was no obvious steaming from the engine.

now we have only 25psi on 4 cylinders and 45 on the fifth. the car obviously turns over but will not start

All I am trying to figure out is how likely this might have damaged more than just the head and head gasket.

bearing in mind the trade in value of £2000, , is there not an known issue with these engines and liners cracking ?

Anyway thanks again smile

liner33

6,101 posts

124 months

Tuesday 3rd October
quotequote all
I would be looking for a new engine before committing to removing the head personally

Water in the oil + compression this low means you could chuck a whole lot of money at it and still have to write the engine off

GreenV8S

24,745 posts

206 months

Tuesday 3rd October
quotequote all
The thing is, either it suddenly and catastrophically damaged all cylinders simultaneously, or it happened gradually with such mild symptoms up to the last moment that you weren't aware there was anything at all wrong, it drove perfectly normally, no sign of overheating, no warning lights, no oil contamination. Neither of these options feel particularly likely to me.

I can see how the engine could have overheated due to lack of pressurisation, but the experience you describe doesn't include any of the normal symptoms. There are plenty of reasons for an engine to stop not related to head gaskets etc.

You have some extremely unusual compression test results and that's worth following up. Despite your confidence, I'm still wary about taking those figures at face value. You have already had suggestions for other tests which would help pin down the type of faults which might cause those compression test results, and a relatively inexpensive way to check for bottom end damage if you're concerned about that.

paintman

3,969 posts

112 months

Tuesday 3rd October
quotequote all
My guess?
Overheated.
Warped head.
Remove & examine. Don't forget to check block face as well.


Edited by paintman on Tuesday 3rd October 20:04