Best pressure & vacuum testers according to redditors

So, the easy bit is determining if there is a vacuum leak at all, there are cheapo gauges on amazon [link] and they are also normally borrow-able at autozone. To test, disconnect a line (the one feeding the EGR valve is easy to get to on the 89') and see what the gauge says. If its reading low at idle, you have a vacuum leak. Here's some poorly lit photos: https://imgur.com/a/VmSWFzd it should read like 18 inches of mercury at idle, but that varies based upon altitude and to an extent, outdoor air temperature. Its a quick test. Finding the leak is less fun. Its generally the small rubber interconnects on the vacuum manifold.

The four basic things every engine needs to run are fuel, spark, timing and compression.

It looks like you've got fuel, and spark which leads me to believe it could be compression or timing. Can you get a compression tester to see what it's getting?

If you find that you have compression then it's probably the timing that you're going to have to fix. And that's WELL out of my wheelhouse of knowledge about engines so someone else smarter than I would have to help with that.

I know you say you've got a lot of experience with small engines but sometimes it helps to go back to basics and start small.

First off, if there are any mods, I would not buy it. HOWEVER, if the mods are basic, cold air intake, headers, exhaust, then thats pretty easy stuff. Step by step though I would do this.

1. Make sure the car is cold, meaning that it hasn't been warmed up before you arrived.
   
   
2. Check the oil.
   
   
3. Check the trans fluid.
   
   
4. If is it warm, then look under the car for any fresh oil or anything else that might have leaked out.
   
   
5. Check under the hood (and I DO mean under the hood. Open it up and make sure the insulation is free of oil or any other liquids that have been splattered on the underside of the hood) and anywhere else. Oil leaves a pretty dark stain where ever it hits.
   
   
6. Do a compression test (http://www.amazon.com/Actron-CP7828-Professional-Compression-Storage/dp/B00020BM28) something like this. This will tell you a lot about the engine.
   
   
7. If they won't allow you to do this test, then walk away.
   
   
8. If the compression is good, then take it for a test drive. low speed, around town, test the brakes (not too hard) and basically go through every gear.
   
   
9. MOST IMPORTANT dont listen to what they have to say about the way it drives, take your own notes. This way you can lower the price based on what you just drove.
   
   
10. Feel the tires, and by this I mean run you hand lightly over the treads. If it feels wavy, then the tire is out of balance. If you feel bald spots here and there it means the shocks are not working as they should. If it feels worn on either the inside or outside of the tire then the alignment is off. All of these things will effect how the car drove when you tested it. Again, these are thing that the seller might not have known about and it only works in your favor.
    
    
11. And this is a tough one. Look for where the paint isn't all the same around the car. Cheap paint jobs usually cover up accidents. I would suggest looking up a youtube video on how to spot the differences, but its better then me trying to describe it.
    
    
12. Look for how the panels line up. For example, if you are in front of the car, and the gap between the hood and the headlight on the left compared to the one on the right is off, then that says either the hood has been off for some reason, or this car rear ended someone on a certain side. Again, youtube it to see.
    
    
13. Anything that you aren't sure of, electrical, engine noise, does the engine shake at idle, exhaust leaks, do some research online. heres a great link for future mods/projects http://honda-tech.com/
    
    
14. If the seller seems eager to sell you the car, watch out!
    
    Hopefully you do read these steps, and again they are 14 simple steps that NO mechanic will argue with. If a seller isn't willing to let you do any of these tests, then you do no want to buy that car.

Go to your local autoparts store (or call) and ask if they have tool rentals. If they do see if you can rent one of these with an adapter for a VW. Wipe dry as much of the coolant as possible then pressurize the cooling system to 10~15psi and start searching for the leak.

Is it low on coolant? does topping it off fix the problem?

Is it hotter when you are driving at speed, or just sitting at a light?

Definitely fix the radiator leak. You say it's leaking around the 'high pressure connection', do you mean where the bottom hose connects to the radiator? Since you just replaced the hose, double check that the clamp is tight enough.

Those plastic tanks (ends of the radiator) are notorious for cracking. Sometimes it can be an obvious crack, or just a small seeping crack that's hard to see, especially with the radiator in the car. If that's the case, a lot of times it makes more sense to get a new radiator rather than replace the tank. It's not that much more expensive, and sometimes it hard to get the tank to seal correctly without the right equipment.

It can also be hard to see the leak without a pressure test. I just realized how expensive the testers are, any good shop should have one, and they should test it for free if you want.

good luck!

-radiator shop family business, worked there every summer growing up.

TL/DR - Is it low? Fill it up. Fix the leak. Radiator shop.

Well if there is a puddle, then it's safe to say that's where your coolant is going. If you are crafty, you can take off the plastic panels underneath the car and have a look for leaks. If you want to go pro level crafty they make a tool that you can use to put pressure on the coolant system. When you put pressure on the system, you will definitely be able to find the leak.

Water pumps usually have a weep hole to warn you when seals are about to fail in the pump. It look like it might be starting to leak down and go around the crank. Sometimes the bolts can leak, they are usually ones that are sealed because they go into a water jacket and the Teflon has degraded. Honestly my experience is that you might as well change the pump at the same time anyway.

A real garage will hook up a pressure tester to the system and simulate running under the hot condition when most leaks occur or are much more pronounced. If the system loses pressure, there’s a leak. Usually you can find it but it takes a careful eye. They can test the cap with the same tester...

Something like this but probably a snap on or mac
Astro 78585 Universal Radiator Pressure Tester and Vacuum Type Cooling System Kit https://www.amazon.com/dp/B0042KOK28/ref=cm_sw_r_cp_api_bks.BbANYKRFF

There are test kits that screw into the filler cap opening and pressurize the system. That's probably your best bet.

Mityvac MV4560 Radiator/Cooling System and Pressure Test Kit https://www.amazon.com/dp/B003V9L05G/ref=cm_sw_r_cp_apa_E3ZDzb1VSDBWC

If that doesnt work, you can add UV dye to your coolant and search with a black light. I've seen people crack open a yellow highlighter on the cheap. Just be sure to do a coolant flush afterwards.

Yeah it's a coolant leak allright then.

Techniques for coolant leaks:
Pressurize the system, listen and look. Maybe not this one, but you get the idea:
https://www.amazon.com/Mityvac-MV4560-Radiator-Cooling-Pressure/dp/B003V9L05G/ref=sr_1_2?s=automotive&ie=UTF8&qid=1504476535&sr=1-2&keywords=coolant+pressure+tester

UV dye. Same, not a recommendation, just a link to the concept.
https://www.amazon.com/FJC-4972-Fluorescent-Leak-Detection/dp/B008QEYTZ4/ref=sr_1_2?s=automotive&ie=UTF8&qid=1504476572&sr=1-2&keywords=coolant+UV+dye+kit

But with your rate of draining, you should be able to find it just by eyeballing. Bet that engine compartment is cramped. 'Course they make stuff for that too. Mirrors on sticks, borescopes.


Jags love to mark their territory.
Check the radiator, hoses, especially where they connect or have a junction. Check the water pump.

Yeah I thought about grabbing a coolant tester. Might try the Mityvac brand from Amazon.

https://www.amazon.com/Mityvac-MV4560-Radiator-Cooling-Pressure/dp/B003V9L05G

First, go rent or buy a cheap compression testing kit to check your current engine and any "new" engine you may get. Compression can tell you a lot about the health of the engine. It's easy to check too. Just remove the spark plug and power to the distributor then screw in the compression test hose into where the spark plug was. Now you can try to start the engine to see if the compression is good. I would let the engine turn over at least three times before looking at the reading. Anything under about 90 PSI indicates a bad cylinder. Something like this should work great.

If your current engine still has compression then there is probably something relatively easy that can be fixed to get the motor going again. What symptoms are you experiencing that makes you think the current engine is done?

STINGER Brand EVAP Smoke Machine Leak Tester with EVAP Adapter & TWO Smoke Tips. Tests EVAP, Intake, Exhaust, Vacuum Lines, Manifolds, etc - Stinger Brand is The BEST CHOICE in Smoke Testing!!! https://www.amazon.com/dp/B0758ZRBT7/ref=cm_sw_r_cp_apa_k-z0BbC232NF2

So I built mine from a paint can. It is very delicate. I suggest you build one from an ammo can or you get one from a paint sprayer like the link. I spent about 150$ and 8 hours making mine. It has advanced features like the pressure gauge and flow meter. But I have never used these in practice. I have used the adjustable regulator though.

Now here's a sensible answer. Thank you good sir. I was just reading about this as well. I think I will pick this up: https://www.amazon.com/gp/product/B01GHD0NAK

$45 from amazon. This one can be used on many cars and trucks too. It's a nice quick little diag tool that can save you tons of money in the long run. I'd charge you $65 for a diagnostic (Labor)
http://www.amazon.com/Mityvac-MV4560-Radiator-Cooling-Pressure/dp/B003V9L05G/ref=sr_1_1?ie=UTF8&qid=1368137222&sr=8-1&keywords=radiator+pressure+tester

Good idea. A friend also suggested a cooling system pressure tester. Example: https://www.amazon.com/Mityvac-MV4560-Radiator-Cooling-Pressure/dp/B003V9L05G/ref=sr_1_1?ie=UTF8&qid=1486473117&sr=8-1&keywords=cooling+system+pressure+tester

I suspect you have a leak somewhere else, as long as it's not overheating or running too hot, you should be able to get it to a dealer without issue. They'll pressure test the cooling system and find the leak, likely a bad o-ring or hose clamp. Or you can do it yourself with one of these: https://www.amazon.com/Mityvac-MV4560-Radiator-Cooling-Pressure/dp/B003V9L05G Just don't go past your system's max pressure or you may blow out a seal or o-ring. Good luck.

You can go to Sears and buy a compression tool or rent one from an auto parts store. There is no point in spending money on labor for easy stuff.

http://www.amazon.com/Actron-CP7828-Professional-Compression-Storage/dp/B00020BM28/ref=sr_1_1?s=automotive&ie=UTF8&qid=1332346828&sr=1-1

Intake manifold gaskets are a very common failure on these engines, especially if the coolant has not been changed per the maintenance schedule during the lifetime of the truck.
If you take an inspection mirror (small mirror on a stick) and investigate the back of the engine above the bell housing you may be able to see liquid coolant; if so, replace the intake gasket.
If you cannot see liquid coolant, you can have your cooling system pressure tested to identify exactly where the leak is occurring. This is a quick easy test, generally less than $20 at any repair shop; or you can buy a pressure test tool set for around $60 and do it yourself.
http://www.amazon.com/Stant-12270-Cooling-System-Pressure/dp/B0002SRGWU/ref=sr_1_1?ie=UTF8&qid=1376069057&sr=8-1&keywords=stant+cooling+system+pressure+tester

You will either need to buy or rent a pressure tester similar to this
Stant 12270 30 Pound Cooling System and Pressure Cap Tester https://www.amazon.com/dp/B0002SRGWU/ref=cm_sw_r_cp_apa_i_32KlDbW0PBJAN

11v when you hit the starter sounds normal, as the battery is under load. What does it read when you are not pressing the starter?

Oil light should be on when the bike is not running, that's normal.

Have you tried a push start? Find a hill, roll down hill with ignition on, drop it into 1st or 2nd and let the clutch out rapidly.

To check for spark you need to remove a spark plug, put the plug back in the wire and hold it against the engine while pressing the starter button. Wear gloves to avoid a nasty shock. Might be worth doing this for all plugs to make sure you are not dropping a cylinder.

A compression tester is pretty cheap. You want to make sure all cylinders have similar levels of compression. You can check the specs to see what compression it had from the factory, however it's more important that the compression is equal between cylinders than matching the factory spec on a 20 year old bike.

You can also try removing the air-box and spraying starter fluid directly into the air intake while pressing the starter. If the bike will run while you are spraying but dies when you stop then you have a fuel problem. Check carb floats, failing that clean (or replace) the jets.