Compression Test - Impending Doom, Options/Advice?

Hi all,

Fairly new to the forum but first post. Usual spiel of hoping I’m in the correct section, and I have searched the forum and the internet for answers but am still not certain of what to do. So here goes…

I’ve got a '93 1.8 Eunos and a few months back had a fairly rapid overheating issue whilst driving, with the gauge increasing and decreases loosely with revs (suspected water pump issue) before rocketing up off the gauge. Soon after, I saw steam from the bonnet and with a minute was able to safely pull over. Fast forward a few months of not driving and I have narrowed the coolant leak to the water pump and oil cooler pipe, as well as a bad radiator cap seal.
Before I forked out to get the parts (waterpump, pipes, gaskets etc. as well as extra bits that should be done at the same time) I thought I’d better carry out a compression test as the car did get very hot. There are no indications to head gasket failure, but car has been idling slightly rough since I’ve had the car (almost a year).
Results were -
First compression - 50 25 25 50
Peak compression - 160 150 125 150
Wet - 195 175 165 180

Noticeably the third cylinder is poor, but I’m not too sure on how to take these results, or what the issue may narrow down to, which is where I’m seeking advice.
I did notice a ‘puff’ on each compression of the 3rd cylinder, sounding as if it went through the exhaust…

The engine is only on 75k miles which is a shame, but I’m also wondering whether it’s worth a re-build as it looks like significant work may need to be carried out, and I intend on keeping this car for a long time.

Sorry for the long post - tried to get my last months’ thoughts and ramblings down in words and seek advice on the compression results and next steps.

Cheers! James.

I’d suggest you now move on to having a leakdown test carried out. That should help pinpoint where the problem lies.

But even then, unless you find the car unpleasant to drive eg simply not pulling properly or something really noticeable like that, I wouldn’t worry too much and just carry on as before.

It’s kind of a catch 22, as I dont have the gear to do the leak down test, and it gets hot quickly due to the leaks so I cant really drive it to do one. But as you say, it pulled well before the leaks/overheating so maybe it is worth spending the £170 ish on parts and get it done. The only thing on my mind was spending the time and money to fix it, and then the engine deteriorating quicker than I’d like. But whether that’s a matter of months or years, I dont have a clue!

Thank you for your reply, much appreciated.

It’s a bit worrying that there’s such a wide spread of results but if it can’t be resolved by a head gasket change, you’ll almost certainly find a swap for another used engine is cheaper than a rebuild of the original.

True, but I’m wondering if I were to go down that path, it could be worth spending the extra to know that the engine will be good as new with a re-build, as opposed to trusting that the swapped engine is in good condition. Maybe getting some quotes are in order for a re-build, and that might put me off!

I would only rebuild and engine if you wanted to know its exact condition. The market will be awash with used engines which are usually in good condition.

1 Like

I guess you’ve gotta trust them and the people selling them that they’re in good condition, as with anything second hand. It might be the best option, besides repairing the engine that’s already in the car. I may do the work on this one and drive it 'til it gives up the ghost…!

Had this as well around 5 years back with my Mk1, which I still have.
Difficult as it was than to pin down over-run smoke, and initial start up puffing, it turned out to be cracked oil rings, for which these mills are known. Your mileage however is so low, it makes me wonder about the valve stem seals first.
To be 100% clear, I am not saying that is your issue, but something only to consider.
I had my head off, sent to of all people a local Honda bike engine business to made a superb job of renewing the head. To no avail. That’s when we knew the oil control piston rings were shot.
The result was, I bought a mill from a well respected source, one of the last production year 1840cc Mk1 mills, and thankfully known to have a proven 50-odd thousand on that had been rear-ended. 2 hours out, 4 in with the renewed head and it’s been an epic mill for years now.
We exchanged the heads. There was no chance I was going to give up essentially and expertly £300.00 revalved & ported head. I’ve no idea what performance advantage if any I’m getting now, but suffice to say, as an Auto, it is quite capable of playing keepy-uppy with any manual of the same vintage …on kick-down with HOLD on and if circa 18-odd mpg is…ok…for a few gallons.

As has been said, there will be plenty decent mills out there…but please do exercise extreme caution source wise. Lots of good guys, lots of cowboys who just stream clean them as " rebuilt". While spare engines are reasonably available still, I really do not think the expense, time, and general angst can justify a rebuild unless…matching numbers are crucial to you.

I’ve never had any issues with it starting, or excess smoke. Just a puff of air through the exhaust whilst carrying out the test which I thought was odd.

To take the engine out, hopefully fix the issue and put it back in must’ve been a nightmare for you! At least you got there in the end though. At least by getting a trusted replacement engine or complete rebuild (although expensive) you know the problem should go away…

Due to not narrowing down exactly what it is, I’m still thinking fix the leaks for around £170, and get it back on the road for the time being. I’m going to make a few calls to engine shops just to see what prices are like for repairs first, as second hand 1.8 engines seem quite sparse at the minute.

Thanks for your reply!

James, I was not the industrious clever one!
I’m afraid I just wrote cheques, but at least to a proper bunch of time-served old school engineers.
The mill was £150.00 delivered, add the ported head @ £300.00, then £400.00 in labour. However, I did recover some costs by flogging ancillieries.
Come to think of it, I got a bit mixed up earlier…ended up with two ported heads!
Bought another one which had also been renewed & ported…it was a busy period in my life!
Long story…moving along now!

The difference in your compression readings are a little worrying but it’s a low mileage engine and it’s not been smoking or anything like that which would indicate you’ve got a decent mill.

I would be thinking head gasket particularly if it’s over heated, sitting won’t have helped either.

If it were me I’d take that off and have a machinist take a look at it. You can then decide on refurb or just clean and reseal with a new gasket and studs and recheck the compression.

It’s a total lottery with used engines unless you can get one out of a running car that’s either rusty or been bumped.

If you trust the engine you have id be inclined to put the cash into it as it will likely need less effort putting into it than completing a full swap

Thanks for the response Montana. I think that’s a good shout. Now I’ve got a bit of time off I’ll start stripping it down so I can have a closer look. If things get too bad, I’m already well in there to rip it out anyway! All I’ve got is time, and I’ve never done anything this involved before so will be good to learn something.

No worries, just takes abit of patience and confidence. The Mk1 is a nice little car to learn on. Work clean and be methodical in your strip down to remember where everything goes and don’t skimp on the quality of your parts.

Definitely keep us posted how you get on!

Yeh I already plan on getting genuine parts. Cheers for the advice, and I’ll definitely let you know how I get on. Nothing worse than reading threads and never knowing how it turned out!

Take lots of photos before and as you strip it down, mainly as an aide mémoire for re-assembly; you don’t need to post them here, but we’d still be interested.

This is where I’m at at the moment. No obvious sign of head gasket failure, going to check if all the valves seal when I turn the cams tomorrow. Long old process, this!

1 Like

Nothing like getting stuck in, well done!

1 Like

Cheers! Did the test where I put spark plugs in (only cylinders 1 and 3 so far), and put some fuel in the flipped over head, to check the valve seals, and whaddya know… Number 1 held nicely, number 3 (low compression cylinder) poured straight out of the exhaust valves and through the manifold port. Gonna test 2 and 4 tomorrow, but looks like I’ve found the culprit. Will be sending to an engine shop to check the head, and get them to do valves (and stem seals whilst it’s there).


Been there.
Recommend OEM head gasket only…expensive.
Please don’t ask how I know!
Cambelt & water-pump ( Gates belts are good, but OEM pump) optional.

1 Like

That shouldn’t be too bad cost wise and least you know it should be good for a good few miles when it’s sorted.
Glad you seem to have found the cause!