windcheater Posted June 25, 2004 Share Posted June 25, 2004 I thought i would ask you lot for some opinions, as I am a bit stumped..... I have a VVC engined '99 Caterham which has done 7,000 miles. The oil pressure has been dropping off slightly, but suddenly it has started dropping right down to just above the red on the Oil Pressure Guage, when idling. I'm finding it quite difficult to measure the oil level with the dipstick as the curve in the tube seems to distort the reading a bit, but it seems to be ok. Its not leaking oil anywhere, and it was serviced last august nad has only done 3500 miles since. i have a new oil pressure sender on order, but was wondering if anyone has aother suggestions if i draw a blank with this?!? confused!! *confused* Link to comment Share on other sites More sharing options...
Peter Carmichael Posted June 25, 2004 Share Posted June 25, 2004 It is either the sender or it is an engine fault. You knew that already. Pressure at idle isn't the big problem. If you still have decent pressure when running you're fine and it is a better indicator of engine health. A sender/gauge fault could cause spurious mis-readings at idle or at running speeds. If there is any sign of tappety noises from the top end, don't risk it. What has changed? What oil do you use? When was it changed? Are you using the car on longer journeys so the oil gets hotter? What is the oil pressure at idle after a cold start? Link to comment Share on other sites More sharing options...
neil.cavanagh Posted June 25, 2004 Share Posted June 25, 2004 windcheater, I just did an oil change on my 1.8 K (140bhp roadsport) and the oil pressure at idle when warm is also only just above the red line. However when revs are higher it is fine, in the normal 'straight up' position.... So I'm not concerned. I've put it down to lovely new oil be a little more 'runny' then the old stuff... Link to comment Share on other sites More sharing options...
windcheater Posted June 25, 2004 Author Share Posted June 25, 2004 pressure when running at high speed is just short of half way on the pressure guage, but it was halfway to the next white line when i got it, and was running higher pressure at idle and high speed/revs. Theres no tappety noises at high revs, and the car is used mainly for journeys of 100+ miles, at much varied speeds. the oil is whatever was put in at the last service (done by caterham cars), although it has been topped up (after it started losing pressure) with mobil 15-40w. If i had changed the oild totally for the above oil, i wouldn't be too concerned, as it is probably more viscous than the standard oil. Its the fact that its reading lower pressures all round than it was 6 months ago, with no visible signs of leakage. My only other thought is that it is burning oil at a silly rate, but only a little puff of white smoke at start up doesn't seem to back this up, in conjunction with the fact that i have only done 3500 miles! i am thinking I will change the pressure sender, and then, if it still worrying me, I will be back.... Link to comment Share on other sites More sharing options...
Myles Posted June 25, 2004 Share Posted June 25, 2004 Theres no tappety noises at high revs What about at idle... I think this is what Peter C was on about... Keep BC free and open for ALL. Membership No. 43xx Alcester Racing 7's Equipe - 🙆🏻™ Alcester-Racing-Sevens.com Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted June 25, 2004 Leadership Team Share Posted June 25, 2004 In the Caterham installation the sump volume struggles to prevent occasional oil starvation, especially in the 1800 installation. If oil starvation has been a regular occurence - track use or fast road use, then over time the oil pump can wear due to the oil / air mix that is created as the pump draws air. This will not necessarily lead to a failure of the pump, but can lead to a small loss of pressure. Fitting an Apollo can slow down wear by reducing the level of air in the oil. Swap the sender, but if it shows no improvement then it may need a new oil pump after a few 1000 more miles? Stu. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted June 25, 2004 Share Posted June 25, 2004 Stuart, Aren't you talking rubbish? The apollo is on the pressure side of the pump, so does not prevent air in the pump so cannot slow down wear in the pump. I genuinely don't understand what you're getting at. Pound to a pinch of... it's the sender in this instance. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted June 25, 2004 Leadership Team Share Posted June 25, 2004 But Peter, the Apollo will reduce the air in the oil, not eliminate it. Once air is in there it is continually pumped around until it is dispersed, even with full submersion of the pick up pipe. Without the Apollo the level of air in the oil will be higher therefore wear of components, including the pump, is increased. ie. Air in the oil returning to the sump in an Apollo installation, will be less than without an Apollo, and hense the same applies going through the pump. Link to comment Share on other sites More sharing options...
windcheater Posted June 25, 2004 Author Share Posted June 25, 2004 Myles, i should probably actually read things instead of skimming you mean?!? 😬 Possibly a bit tappety at idle, possibly more so than when its warm...... Oil pressure guage reads middle when started from cold, presure drops off as oil warms up. I will chaneg the sender, then I will investigate the pump if that makes no difference. i may also drain the oil to make sure i have the right amount in it. i'm really not convinced by the dipstick readings either! Link to comment Share on other sites More sharing options...
Peter Carmichael Posted June 25, 2004 Share Posted June 25, 2004 Stuart, I think you live on a different planet if you believe that air pumped around the galleries and drained back to the sump is significant compared to windage. Your analysis is a fiction. In case you haven't noticed, this is a personal attack on your integrity, so let the flaming retributions begin. 😬 ... or alternatively explain to me why I am wrong and I will gladly change my mind. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted June 25, 2004 Share Posted June 25, 2004 Should also comment that if you have concerns the best bet is to drop the sump and have a look for anything untoward. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted June 25, 2004 Leadership Team Share Posted June 25, 2004 Peter, somebody must have rattled your cage this afternoon Windcheater has a gauge suggesting low oil pressure. Could be the sender. Could be the pump. Could be a number of differing things? I didn't realise that you had written the bible on K-Series problems and any suggestions or theories put forward by other owners need to be taken as utter bo**ocks? I respect greatly the knowledge you have regarding the engine and your readiness to give advise wherever it may help a fellow owner. However, if you're having a bad day, please don't lower yourself to becoming a sad individual like some others on this forum. From this point I'm out of the discussion. Link to comment Share on other sites More sharing options...
Tony C Posted June 25, 2004 Share Posted June 25, 2004 Just to throw in my two-ha'peth - a pump does not give pressure; resistance to flow provides the pressure. Therefore, if the low pressure indicated bt the gauge is accurate, it's likely to be caused by clearances which are too large. What's-up stu, couldn't you detect the tongue in cheek 😬 BRG Brooklands SV 😬 It seems that perfection is achieved not when there is nothing more to add, but when there is nothing more to take away. (Antoine de Saint-Exupery) Link to comment Share on other sites More sharing options...
Mick Day Posted June 25, 2004 Share Posted June 25, 2004 Actually pressure is a product of the pump output & resistance to flow. So if the pump is damaged & can't maintain output........................... .................. & yes I'll put my money on the sender being U.S. Link to comment Share on other sites More sharing options...
Tony C Posted June 25, 2004 Share Posted June 25, 2004 Yeh - sorry Mick I was in pedantic mode. A pump can only give flow rate - resistance to flow gives pressure. If the pump is not healthy it will ultimately result in a drop in pressure in the liquid, but it's because the flow rate is decreasing. You cannot buy a 100 psi pump - they are rated in flow rate (ltr/min). Considering the known anomalies with the 7 oil pressure indication system, it's most likely to be a sender or gauge problem. I "Cured" my poor oil pressure indications by going to a mechanical gauge. The added advantage is that the gauge is 0 - 100 psi. The reading is rock steady at the varying conditions: cold idle, cold running, hot running and hot idle. I think gauges reading in bars are ineffectual because of the inappropriate scale. Gas in the oil causes problems because the oil film in the bearings becomes too "Thin" because the gas bubbles are easily compressed and in the pum can cause cavitation and physical damage to the pump. Is the K-Series oil pump a type of spur gear pump? BRG Brooklands SV 😬 It seems that perfection is achieved not when there is nothing more to add, but when there is nothing more to take away. (Antoine de Saint-Exupery) Link to comment Share on other sites More sharing options...
mic Posted June 25, 2004 Share Posted June 25, 2004 It may not be the problem in this case , but its not unkown for the foam baffle to break up and block the pickup. Link to comment Share on other sites More sharing options...
thinfourth Posted June 25, 2004 Share Posted June 25, 2004 When did you last change the oil in time not miles as you migh have a wee bit of fuel ending up in the oil dropping its viscosity this is very common in marine diesels running on gas oil. Sod the heater wheres my shades Link to comment Share on other sites More sharing options...
Gridgway Posted June 25, 2004 Share Posted June 25, 2004 an astounding coincidence thinfourth. I was just thinking earlier this evening that my Caterham needed an upgrade. And I finally settled on a more reliable engine, a marine diesel. How strange is that??? What do you recommend? I am a bit worried about the engine oil viscosity though? As well as the effect of the salt on the aluminium. Mind you, as torque is more important than BHP, I think I'm on the right track. Graham Link to comment Share on other sites More sharing options...
windcheater Posted June 30, 2004 Author Share Posted June 30, 2004 well, you'll be glad to know that its all sorted anyway....... as it turns out, the sender was faulty, and after replacing it, the pressure is now reading very healthily indeed. Changing it was also much easier than i thought 😬 😬 thanks for all the help though guys Link to comment Share on other sites More sharing options...
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