Where am I losing oil?

[V7 SLR]

Suggestions please.

 

Until this year V7 used no oil. Each oil change exactly the same amount of oil came out as was put in. It never ran low and never needed a top up.

 

Over the Winter I had the head off again, to fit new cams primarily. The valves were the same as last year and although I did pop them out to give them another quick lap (doesn't hurt), they were replaced without any problems.

 

I've never had the bottom end apart but the engine was left "topless" for a few months, during which time it was kept dry and free from dirt.

 

This year I was initially caught out by the amount of oil I appear to be using. The Spa gauges are so accurate that I became alarmed when at idle the oil pressure dropped very low. This happened a few times until I checked the oil level and discovered it to be low. Since then I've topped it up a good number of times, so I know I'm losing it somewhere. I fill it up and the oil pressure returns, even at hot idle, for a while at which time I must have lost oil somewhere and the oil pressure starts to go down at hot idle. This happens alarmingly quickly. Over a period of 200 miles or so.

 

In other words, on the forthcoming Italian tour I will probably use over a litre per day... or a litre per tank of fuel. Gulp.

 

Observations:

 

1. I can find no evidence of oil in the cooling system.

2. I can't see any evidence of oil burning (the exhaust fumes are clean).

3. I can't find any leaks.

 

Given the first and last observations, it must be burning oil right? If so, how is it getting through to the cylinders? I would guess one of the following:

 

Valve guide seals

Piston rings

Head gasket breach between oilway and cylinder.

 

If it was the latter, I would expect problems with the oil system (wouldn't I?) like excessive pressure venting from the dry sump breather, or my cam cover breather cover (I haven't uncovered the breather yet) would pop off). I still have net vacuum in the head as indicated when I remove the vent cover, so I don't think it's the latter problem.

 

I had a leakdown test last time I was at DVA's. It showed V7 to be in the "normal" range but at the upper end of it. Compression is high and consistent across all the cylinders.

 

Help please.

 

Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours

 

[Myles]

Oh bugger! ☹️

 

Can't help obviously - but glad the SPAs are accurate 😬

 

Not coming out of the remote pressure kit I hope (just found out that I probably have the bespoke Caterham item - as an Academy car - and therefore the hoses etc. are not necessarily necessary.)

 

Hope you fix it. Ordered the LEDs BTW...

 

REgds,

Myles

[V7 SLR]

Not coming out of the remote pressure kit, no. No leaks at all.

 

Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours

 

[SLR No.77]

Nig,

 

Go through everything carefully in an analitical manner - it can only be lost through a finite number of routes:

1. You're burning it

2. It's going into the coolant system

3. It's leaking out somewhere

 

3 is easily covered - check everything and everywhere - including inside the timing belt cover, underneath, on top, around the starter entry to the bellhousing etc etc.

 

2 is assessed more easily over time - if it is going into the coolant system then it isn't going to get out. The longer you leave it the more contaminated it will become.

 

Therefore the conclusion - assuming you've covered 2 & 3 - is that you must be burning it. If it is a slow but steady loss, then it could be possible that it would be hardly noticed - do or the usual checks on the rings, valve stem seals etc - drop down from a good speed in top gear with your foot off, then dip the clutch and boot it - does it chuck out blue smoke. You need to determine whether the burning is intermittent such as blue smoke on the over-run, or steady - no real evidence of burning at all. If there is no obvious burning then you are likely to have a "steady" leak from something such as the cam carrier, which I'm sure you are aware can be a bugger to seal.

 

There's nothing here you don't know - sometimes it just wants re-stating

 

BTW, the paint on your old rear wings came off really easily with Nitromors - 1 application for the blue, 1 for the primer, then a 3rd applied and scrubbed with a nylon brush to remove any deposits from the weave. If your cf nose is the same water-based paint it would easily be stripped in an evening 😬

 

Stu.

[V7 SLR]

Stu,

 

Must be burning. No drops on the garage floor and coolant fine.

 

However, nothing noticeable from the exhaust. I'll ask the Italian tourers to keep their eyes on it. If it is the bottom end I'll probably go for a full rebuild this Winter, including a Scholar monoblock/liner set and new pistons. Mine are SLR-standard which means they're not fully floating. I'll also go for uprated bearings wherever possible and a steel oil pump rotor.

 

Seems like a good way to waste even more money on V7. The paint job will have to wait... or do it myself (now there's a thought).

 

Glad the wings came up OK. I'll have a go with the nose over the Winter too I reckon. Do you need to sand it once you've wire brushed it or is that the last job? What abou t finishing it then? Does it need relacquering once it's stripped? If so, what do you recommend? I'm a total novice at painting and finishing.

 

Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours

 

[Simos]

A litre per tank ?! That's a two stroke !

 

You'd see a litre/200m physically leaking.

 

Only thought, is there any witness oil underneath the car, if it were a vapour emission from low down on the engine it could coat the bottom of the car without being directly visible. I'm actually assuming you've looked and that said would leave drips on your garage floor, but we are at wits end here...

 

If you're burning it at alow rate so it's not directly visible try the sunglasses test for breathing. Place something white close to the exhaust outlet and run the engine for a while. If there's a litre of oil per tank in it, it should soon leave a very dirty oily mark I would have thought ?

 

Good Luck, Simon.

[Peter Carmichael]

Have you ruled out a wormhole in space-time...?

 

My guess would be rings, which might also show up as excessive breathing out at the catch tank.

[R2D2]

 

Oil use to this extent with highish compression is quite confusing.

 

I would do another compression test as soon as possible. If you get a low reading with a dry test put some paraffin in each cylinder and try again. If the compression rises you probably have valve trouble, if it is still low probably bores.

 

Are you sure that the engine hasn't been over fuelling and suffered from bore wash?

 

Does the oil in the tank seem contaminated with fuel?

 

 

[V7 SLR]

Chris, it is entirely possible that the map is out. It was mapped when I had bad cam timing. Now that it's sorted, the map is definitely out a little, although I suspect not a lot judging from the performance. It has a thrumming sound at constant speed/low load site which I take to be incorrect fuelling. During the mapping session Karl had to take out a lot of fuelling. It is possible that now the cam timing is right thatmore has to come out.

 

Could bore wash really be the reason why I'm using so much oil?

 

I am of the opinion that the bores/rings ought not to be the cause because they haven't changed since it was running so well last year. The only reason I can think of for bore/ring problems is that the bottom half of the engine was open all Winter while I sorted the head out. That said, I kept it clean and dry.

 

There isn't any difference between the breathing now and before so PC's comment about rings is encouraging.

 

The head ought to be OK too. It's had enough care and attention lavished upon it.

 

I'll do some tests when I'm back from Italy. Am I likely to damage the engine by running it under these circumstances for 4000 miles? I'll make sure it is kept topped up with oil at all times.

 

Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours

 

[owelly]

I'm sorry to disagree with Chris, but if a dry comp test is low and a squirt of oil/parafin gets a higher reading, then I'd be looking at rings/bores. if a wet test makes no difference, look at top end (head gasket/valve gear etc.)

[Rob Walker]

Nig,

 

Did you replace the inlet valve guides when you had the head ported ? If not there could be as little as 19mm of the original 32mm length remaining.

 

Should be no need to replace your pistons to make them fully floating, its the end of the rod that needs bushing or replace the rods. The pistons should have circlip grooves machined in on the SLR.

[R2D2]

Owelly,

 

Quite right - brain fade.

[oilyhands]

The compression test gave good results dry and the leakdown test showed consistent and good results. The head had 16 new Colsibro guides fitted when ported, its now standard practice for the guides to be replaced, or removed before porting and replaced after. My guess is that the oil control rings are no longer up to the job.

 

The standard spec. VHPD pistons dont have circlip grooves and removing them cleanly from the rods can be a problem, re-ringing can be successful but there are no fewer than three (and with the latest pistons four) different ring sets. Getting the correct ones is not easy.

 

Oily

[SLR No.77]

Nig, if your doing a rebuild over the winter and want to part with the pistons, liners etc (ideally with the rods intact) I could well be interested in the lot. Let me know if you have any more thoughts on it.

 

Did I mention wire brush with respect to the nose I meant nylon brush. Wire wool with a little Nytromors should remove any last evidence of paint, then a light sanding with a very very fine paper. And yes it will need lacquering!

 

Stu.

[V7 SLR]

I really want to remedy the oil problem. If this can be done cheaply, i.e. with new rings and whatever honing might be required of the liners, then I'll probably stick with that. I want to inspect the bottom end bearings, simply because I've never done so. If they're all OK, I'll probably put them all back as they came out.

 

If it is necessary to change the pistons, I'll probably go silly and buy into the Scholar monoblock liner system, new (fully floating) pistons, steel oil pump rotor and uprated bottom end bearings. Although I think this is overkill and hope that it won't be necessary, a bottom end of this nature would remove all questions over strength and durability I have got with my current setup.

 

Expensive however, therefore I'll try a cheaper solution first. As I indicated above, I don't actually think there's anything wrong with the VHPD bottom end. I'm surprised at the sudden and dramatic increase in oil usage which makes me believe I have a catastrophic failure of something or I have buggered up something in the head when rebuilding. If it were a worn ring I would have expected the oil usage to have increased somewhat more gently than it has.

 

Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours