- This topic has 1 reply, 2 voices, and was last updated 12 years ago by
.
-
Posts
-
I am posting this to try and give some comfort and courage to anyone who is contemplating doing an engine overhaul themselves. It really isn’t hard (unless you split the case) and I (70 years young) did it myself in my garage with no “special” VW unique tools although I do have a very large collection of normal mechanic’s tools. A small parts washer is a big help. I have air but it really isn’t necessary. Good light and a lot of horizontal surfaces and a $100 engine stand are required to do a good job.
MiGi now runs well with about 35# oil pressure at 2000-3000 rpm on 10W30 Valvoline VR1 Racing oil with ZDDP on a bright sunny day at 74 degrees ambient. Oil pressure at idle of 900 rpm warm is about 20#. Oil temp on the gauge and with an IR thermometer is 165 F. MiGi had a 1500cc sp – no dog house cooler. It is now a 1600cc sp (still no dog house).
When I bought MiGi, I was told that the engine had 12,000 miles on it. I have no idea what oil was in it. There was no oil pressure or temperature gauge and the little low oil pressure light was not hooked up. I am a suspicious sort and somewhat paranoid about high oil temps and low oil flow having previously had a few oil/air cooled engines. I immediately drained the oil and adjusted the valves. When I took off the valve covers, the insides of them and the rocker arm areas on the tops of the cylinder heads were covered with a sooty like black deposit. This made me very nervous. I cleaned it as best I could thinking the whole time that this sooty stuff was inside the block and possibly in the passages as well. I reasoned (I thought) that the engine had more miles on her than advertised. Decided to put in 10W40 oil. This was late summer when the roads were still hot. Put her back together and finally got the oil light to work. I ordered an oil pressure gauge and oil temp gauge also. Was unhappy to see that my oil pressure was only about 5-6# at idle when warm and about 18# at speed with oil temps at about 210F.
Soon afterward, I ran compression checks on the engine and found that all cylinders were ok except #1 which was about 70# (almost 60# less than the others). Not good. (Strangely enough the engine still started and ran well.) Oil consumption was not measurable, I was changing it almost weekly because of the sooty stuff mentioned above. So, I reasoned that I needed to put in some high mileage thicker oil and went with Castrol 20W50.
Immediately I noticed that the oil temperature went up but the oil pressure was not noticeably different.
Hoping that my oil pump was worn and with too much clearance, I ordered a new larger 26mm gear Schadek pump to replace the original equipment 23mm one. On replacing, it was obvious that the old pump was worn and my clearance readings proved that out. Oil pressure immediately jumped to about 38# with about 20# at idle. It was now January and therefore hard to get a good comparison but, was of course colder than before. Engine oil temp was still running about 210F, which I felt was too high for the running around town <55mph driving. Gave the engine a 4 can engine cleaner and high pressure washer clean. It helped the temp. And It looked a lot better too.
Then one cold morning I started her up but when I got home from a ride, she left me a puddle of oil. I blew either the cooler itself or a seal at the cooler (didn’t know which). My oil was too thick since I was still running the 20W50 but now with a new larger pump and colder weather, I caused the leak myself by overpressurizing – probably before I got out of the driveway. The dread oil leak. That did it! I decided to overhaul the engine and fix the leak and the low #1 compression problem. I was no longer concerned about oil pressure so decided to not split the case unless some other problem revealed itself after I pulled and got into the rebuild.
My son gave me an engine stand for Christmas and so I ordered a Mahle 1600 piston kit, gasket kit, new push rod tubes etc, etc. I had bought 2 heads that had just come back from the shop with new oversized valves, and new rockers and valve springs. I decided to go with a 1600 cc kit instead of larger because my engine does not have a dog house cooler and I was concerned about overheating.
Parts arrived and the engine pull was uneventful using a furniture dolly and a come-along.
No big surprises on pulling the engine apart except to note that it was the seals not the oil cooler that blew. Great! A lot of the tin was missing. None of the head bolts of the rocker arm shafts were tightened to spec – they were all very loose. In fact, I wondered if the last guy to overhaul even had a torque wrench. #1 cylinder had noticeable leakage betweent the cylinder and the head. Since these engines do not have a head gasket, i attributed this leakage to my low compression pressure in that cylinder. #3 cylinder exhaust valve head was about ready to pop off the stem so I felt good about tearing the engine apart for what really was only a oil leak on a good running engine. I also had about 1/3 of the carb to intake manifold gasket was missing causing a vacuum leak. None of my 10mm head bolts were pulling out and I decided that I would not put in case savers and 8mm studs as many recommend since that would involve splitting the case. All clearances on the main journals and end play were in spec. Reassembly was uneventful.
I switched to 10W30 Valvoline oil and cranked it on the starter motor for about 10 minutes with the plugs removed to build up oil pressure (35# on the starter motor) before measuring compression pressures (all at 135#).
Here is the great news: Oil temp is way down now. Why? I can only assume that the larger pump, with the thinner 10W30 oil allows more of it to flow through the cooler. The way that a sp VW engine controls oil pressure is by bypassing the oil cooler if the pressure is too high. So, if you run heavy oil and a good pump with good engine clearances, it is possible that your oil may never even pass through the cooler and would run high temp. I have convinced myself that the prior owner had been running non-detergent oil in the engine and that was the cause for the sooty deposits. Now all is sparkly clean. Also, the vacuum leak at the mating flange of the carb caused a high idle and made the speed and mixture adjustment screws ineffective. Changed the gasket, alls well at 900 rpm idle.
Doncha just love a happy ending? I’m going to do my first 300 mile oil change tomorrow and am staying away from 20W50.Great story, Roy. Glad you’re running cool, and that’s good info re the thinner oil leading to cooler temps.
I do think your vacuum leaks might have played a role in your higher temps though. Suspect the lean condition in #1 was cancelled by the loss of compression, but the intake air leak probably gave you at least two other lean jugs.
Congrats on a successful rebuild.
- You must be logged in to reply to this topic.