Engine Rebuild?

[chrisjcoe]

I've had major battery problems (another thing I need to change but it's not at the top of my list). After charging for over a day, I was finally ready to test. I think I'll buy a decent Ctek charger when I'm paid!

Do dry compression tests first as this tests the valves and rings

On a cold engine, from front to back - 180, 176, 165, 177. Each reading was taken after about 5-6 cranks. Resting the 3rd chamber showed 170 after 8 cranks, and later again showed only 152 after 5 cranks.

pour a little engine oil into each chamber so it seals the rings and do it again

From front to back - 170, 177, 173, 186. I was going to retest the 1st chamber again as I thought the figure should increase, but I'd already hit new territory with the battery life so didn't want to push it too far.

Hissing sound after the engine has stopped could also be simply the compression in one cylinder near the top of the compression stroke leaking to atmosphere, possibly through a slightly-open valve.

This was still noticeable once the plugs were back in and I'd run the engine for 10 minutes to get rid of the oil in the chamber. I'm sure my neighbours loved the oily smoke but what the hell, they're noisily having a bathroom fitted (estimated 2 week job) so I'm just repaying the favour.

If it ever stops raining here, I will do another dry test to see how accurate my first readings were and also get the details on the type of plugs used. What is the ideal compression figure for a perfect engine? What would you expect to see from a 23 year old car?

 

[Hilux]

ORIGINAL: chrisjcoe

I've had major battery problems (another thing I need to change but it's not at the top of my list). After charging for over a day, I was finally ready to test. I think I'll buy a decent Ctek charger when I'm paid!

Do dry compression tests first as this tests the valves and rings

On a cold engine, from front to back - 180, 176, 165, 177. Each reading was taken after about 5-6 cranks. Resting the 3rd chamber showed 170 after 8 cranks, and later again showed only 152 after 5 cranks.

pour a little engine oil into each chamber so it seals the rings and do it again

From front to back - 170, 177, 173, 186. I was going to retest the 1st chamber again as I thought the figure should increase, but I'd already hit new territory with the battery life so didn't want to push it too far.

Hissing sound after the engine has stopped could also be simply the compression in one cylinder near the top of the compression stroke leaking to atmosphere, possibly through a slightly-open valve.

This was still noticeable once the plugs were back in and I'd run the engine for 10 minutes to get rid of the oil in the chamber. I'm sure my neighbours loved the oily smoke but what the hell, they're noisily having a bathroom fitted (estimated 2 week job) so I'm just repaying the favour.

If it ever stops raining here, I will do another dry test to see how accurate my first readings were and also get the details on the type of plugs used. What is the ideal compression figure for a perfect engine? What would you expect to see from a 23 year old car?

I dont know what they should be but I am surprised that number 1 was a lower reading with oil than without as thats now a big difference compared to dry.

 

[chrisjcoe]

I'm going to do another dry test on all of them and wet on 1 again

 

[zcacogp]

As Paul said, I don't know what the figures should be either but that's not that relevant - the more relevant point is the relative readings across the engine. They shouldn't vary by more than 10%, and there shouldn't be more than 5% variation across adjacent cylinders. Your figures seem a little uncertain (due to the battery problems), but those do vary a bit more than this; cylinder 3 when dry shows more than 5% difference to #2 and #4 as well. The fact that things improve when you put oil in there suggests the problem is with the cylinders and bores than the valves.

I'll bow to the (much) greater wisdom of others, but I'd be thinking about taking the head off for a more detailed inspection. (And I am aware that this conflicts with that I have said before!)


Oli.

 

[chrisjcoe]

I'll bow to the (much) greater wisdom of others, but I'd be thinking about taking the head off for a more detailed inspection. (And I am aware that this conflicts with that I have said before!)

Lol! I thought I'd be doing this anyway to be honest, but I seriously cannot afford the bits and pieces for a month or two. Do you think the car is drivable once or twice a week without risking head damage as I don't want to leave it sat for months while I can scrape up the money to get investigating? I don't want to take the head off until I have a gasket waiting to be fitted, and if the head is off I may as well go the whole hog and do as much as I can.

I'm over-cautious here due to a past experience that saw my car being pushed up the M25 Clacketts Lane services slip road by a group of German hikers after my head gasket went. It was a great day. Not only had we just picked the car up from the airport parking after a 9 hour evening flight in which I hadn't slept, but we had to wait for 6 hours for someone to pick us up. All in all it was about 36 hours without sleep, stupidly expensive services food, and the knowledge that my broken car was a 2 hour drive away from my house. All because I had ignored a smoking exhaust for a few weeks.

The fact that things improve when you put oil in there suggests the problem is with the cylinders and bores than the valves.

Bearing in mind my limited mechanical experience, this strikes me as on the more expensive side of engine repair than just replacing a few seals and gaskets. Should I start crying and fingering through the yellow pages?

 

[zcacogp]

Chris,

My thoughts are that if I took some compression readings like that from my S2 then I'd be wanting a reliable opinion from someone who knows what he is talking about. The internet is full of self-proclaimed experts whose advice can only be educated guesswork when they can't see the thing for real. Is it OK to drive the car with those compression readings? Yes, I'm sure it is. I can't think you will do any damage to what is already there, the problems are that it won't perform well, may be thirsty on juice and may use a bit of oil. It's not an ideal situation, but it's also not a tragedy; many thousands of people are doubtless running cars in much ropier states of health without a care in the world. But compression readings like that suggest that something isn't right and if you want the car to run as it should then it's worth having it seen to.

Yes, if the problems are with the bottom of the engine then it will be more expensive than just having the top end rebuilt. But, as I said, find someone who actually knows what they are talking about and show the car to them. You are in Colchester and someone will be able to recommend a good indie near you.


Oli.

 

[chrisjcoe]

Thanks Oli. I had planned to drop the car round my regular mechanic for a check over at some point, so will give him a call to see what he'll charge for it! I did think that if the HG isn't shot then driving would be ok, so glad I have a more knowledgable 2nd opinion to back me up.

 

[edh]

The readings are a bit erratic - your first set (on page 1) looked just fine.

There are a number of possible explanations for oily plugs & smoke - might be worth leaving it with a proper mechanic first.

I still wonder if it's not something simple - ignition related for example. How long since the car had leads/distributor etc.. checked?

 

[chrisjcoe]

I've had the car since July, didn't get much information about it from the previous owner. I think I'll replace the plugs at least, but the £100 for the leads will wait a bit. I think you're all right though, the car needs to be tested on a decent power source instead of my ropey battery. I also wondered if the oily plugs could be because of a prior and recent wet compression test. I'm going to call my local, tame mechanic and see what he has to say!

 

[PSH]

Hi Chris

If I was you I'd ask your local mechanic to do a leak down test as compression tests can for many reasons vary . If your results are correct at 175 that seems pretty low, however they are good in as far as all 4 cylinders have similar readings but IMHO something needs looking at.
Now before I get called an armchair mechanic which to some extent will be true I do my best to research first before speaking, this question has been raised a number of times on the web for the 944 and when talking about the S2 in particular others have reported test readings of around 210psi some higher with others recording approx 190, so from that I'm concluding that yours are below these findings from fellow S2 owners and hence why I say 'get a leak down test done'.
However if money is tight just now and you need the car it's unlikely that any extra damage will be caused due to continued use although your running costs will be higher, do get that leak down test done though, it shouldn't cost much and can answer many questions.

Regards

Pete

 

[chrisjcoe]

do get that leak down test done though, it shouldn't cost much and can answer many questions.

Excellent idea, I'm sure a mechanics tools will be a lot more accurate than mine too!

 

[PSH]

ORIGINAL: chrisjcoe

do get that leak down test done though, it shouldn't cost much and can answer many questions.

Excellent idea, I'm sure a mechanics tools will be a lot more accurate than mine too!

Without insulting the mechanic check that his testing equipment has an orifice fitted in-line, not all makes do ( cheap variants) which then relies on the regulator which is not the way to do things...

good luck

Pete

 

[chrisjcoe]

£25 for compression and/or leak-down tests, reckons it will take him 1/2 hour. I'm happy with that, so will book it in when I'm paid!

 

[PSH]

ORIGINAL: chrisjcoe

£25 for compression and/or leak-down tests, reckons it will take him 1/2 hour. I'm happy with that, so will book it in when I'm paid!

That sounds a very fair price to me.... I'd insist on just the leak down test though, no point in doing the compression test.

regards

Pete

 

[chrisjcoe]

I did wonder that. Leak-down will test loss of compression, but didn't know if testing the build-up of compression was important or not. He'll know what to do though.

 

[PSH]

ORIGINAL: chrisjcoe

I did wonder that. Leak-down will test loss of compression, but didn't know if testing the build-up of compression was important or not. He'll know what to do though.

Leak down can show many things, can show if your valves are sealing properly and if not whether it's the exhaust,inlet or both, can show if HG has failed or beginning too, whether the rings are ok and any leaks can be detected by listening for the compressed air escaping etc, etc

Pete

 

[chrisjcoe]

That sounds pretty helpful. I might tout myself around Ipswich docks for the £25 tonight so I can get it booked in ASAP. It's been a very expensive month with 2 services and MOTs, car insurance and a paying for some poorly done concreting!

 

[chrisjcoe]

Just had about 40 minutes of tests run on the engine. Warm, compression was between 200-210 on 3 of the 4 chambers, the other was about 180-190, so not as bad as my tests suggested. Also there were no hydrocarbons in the coolant. So the advice is that the HG is ok and the engine is relatively healthy. So, until I decide to strip it for a full gasket change and clean probably late next year, I'll leave it well alone. All this and he charged me £0, a bit of a bargain I think. It is booked in wednesday to check out the odd grumbling noise when steering left under power, but he agreed that it wasn't the steering rack. So all in all some quite positive news!

Also stopped by my restoration friend, who will strip off the bodge sill repairs and do them properly for about £250, I thought he meant each side but he meant in total. Currently it has an awful black stone-chip layer on, and he'll put that back over the proper repairs until I can afford a full respray. I took the black vents out and he looked around, the sills inside look fine so that's a big relief. One of the front wings is rusty at the back behind the wheel arch though, and he's suggesting picking up an old wing or panel for that. I'm going to have a quick google for them.